A toolkit for SQLite databases, with a focus on application development
Proudly serving the community since 2015
Latest release: October 13, 2024 • version 7.0.0-beta.6 • CHANGELOG • Migrating From GRDB 6 to GRDB 7
Requirements: iOS 13.0+ / macOS 10.15+ / tvOS 13.0+ / watchOS 7.0+ • SQLite 3.20.0+ • Swift 6+ / Xcode 16+
Contact:
- Release announcements and usage tips: follow @groue on Twitter, @[email protected] on Mastodon.
- Report bugs in a Github issue. Make sure you check the existing issues first.
- A question? Looking for advice? Do you wonder how to contribute? Fancy a chat? Go to the GitHub discussions, or the GRDB forums.
Use this library to save your application’s permanent data into SQLite databases. It comes with built-in tools that address common needs:
-
SQL Generation
Enhance your application models with persistence and fetching methods, so that you don't have to deal with SQL and raw database rows when you don't want to.
-
Database Observation
Get notifications when database values are modified.
-
Robust Concurrency
Multi-threaded applications can efficiently use their databases, including WAL databases that support concurrent reads and writes.
-
Migrations
Evolve the schema of your database as you ship new versions of your application.
-
Leverage your SQLite skills
Not all developers need advanced SQLite features. But when you do, GRDB is as sharp as you want it to be. Come with your SQL and SQLite skills, or learn new ones as you go!
Usage • Documentation • Installation • FAQ
Start using the database in four steps
import GRDB
// 1. Open a database connection
let dbQueue = try DatabaseQueue(path: "/path/to/database.sqlite")
// 2. Define the database schema
try dbQueue.write { db in
try db.create(table: "player") { t in
t.primaryKey("id", .text)
t.column("name", .text).notNull()
t.column("score", .integer).notNull()
}
}
// 3. Define a record type
struct Player: Codable, FetchableRecord, PersistableRecord {
var id: String
var name: String
var score: Int
}
// 4. Write and read in the database
try dbQueue.write { db in
try Player(id: "1", name: "Arthur", score: 100).insert(db)
try Player(id: "2", name: "Barbara", score: 1000).insert(db)
}
let players: [Player] = try dbQueue.read { db in
try Player.fetchAll(db)
}
Access to raw SQL
try dbQueue.write { db in
try db.execute(sql: """
CREATE TABLE place (
id INTEGER PRIMARY KEY AUTOINCREMENT,
title TEXT NOT NULL,
favorite BOOLEAN NOT NULL DEFAULT 0,
latitude DOUBLE NOT NULL,
longitude DOUBLE NOT NULL)
""")
try db.execute(sql: """
INSERT INTO place (title, favorite, latitude, longitude)
VALUES (?, ?, ?, ?)
""", arguments: ["Paris", true, 48.85341, 2.3488])
let parisId = db.lastInsertedRowID
// Avoid SQL injection with SQL interpolation
try db.execute(literal: """
INSERT INTO place (title, favorite, latitude, longitude)
VALUES (\("King's Cross"), \(true), \(51.52151), \(-0.12763))
""")
}
Access to raw database rows and values
try dbQueue.read { db in
// Fetch database rows
let rows = try Row.fetchCursor(db, sql: "SELECT * FROM place")
while let row = try rows.next() {
let title: String = row["title"]
let isFavorite: Bool = row["favorite"]
let coordinate = CLLocationCoordinate2D(
latitude: row["latitude"],
longitude: row["longitude"])
}
// Fetch values
let placeCount = try Int.fetchOne(db, sql: "SELECT COUNT(*) FROM place")! // Int
let placeTitles = try String.fetchAll(db, sql: "SELECT title FROM place") // [String]
}
let placeCount = try dbQueue.read { db in
try Int.fetchOne(db, sql: "SELECT COUNT(*) FROM place")!
}
See Fetch Queries
Database model types aka "records"
struct Place {
var id: Int64?
var title: String
var isFavorite: Bool
var coordinate: CLLocationCoordinate2D
}
// snip: turn Place into a "record" by adopting the protocols that
// provide fetching and persistence methods.
try dbQueue.write { db in
// Create database table
try db.create(table: "place") { t in
t.autoIncrementedPrimaryKey("id")
t.column("title", .text).notNull()
t.column("favorite", .boolean).notNull().defaults(to: false)
t.column("longitude", .double).notNull()
t.column("latitude", .double).notNull()
}
var berlin = Place(
id: nil,
title: "Berlin",
isFavorite: false,
coordinate: CLLocationCoordinate2D(latitude: 52.52437, longitude: 13.41053))
try berlin.insert(db)
berlin.id // some value
berlin.isFavorite = true
try berlin.update(db)
}
See Records
Query the database with the Swift query interface
try dbQueue.read { db in
// Place
let paris = try Place.find(db, id: 1)
// Place?
let berlin = try Place.filter(Column("title") == "Berlin").fetchOne(db)
// [Place]
let favoritePlaces = try Place
.filter(Column("favorite") == true)
.order(Column("title"))
.fetchAll(db)
// Int
let favoriteCount = try Place.filter(Column("favorite")).fetchCount(db)
// SQL is always welcome
let places = try Place.fetchAll(db, sql: "SELECT * FROM place")
}
See the Query Interface
Database changes notifications
// Define the observed value
let observation = ValueObservation.tracking { db in
try Place.fetchAll(db)
}
// Start observation
let cancellable = observation.start(
in: dbQueue,
onError: { error in ... },
onChange: { (places: [Place]) in print("Fresh places: \(places)") })
Ready-made support for Combine and RxSwift:
// Combine
let cancellable = observation.publisher(in: dbQueue).sink(
receiveCompletion: { completion in ... },
receiveValue: { (places: [Place]) in print("Fresh places: \(places)") })
// RxSwift
let disposable = observation.rx.observe(in: dbQueue).subscribe(
onNext: { (places: [Place]) in print("Fresh places: \(places)") },
onError: { error in ... })
GRDB runs on top of SQLite: you should get familiar with the SQLite FAQ. For general and detailed information, jump to the SQLite Documentation.
- Installation
- Database Connections: Connect to SQLite databases
- SQLite API: The low-level SQLite API • executing updates • fetch queries • SQL Interpolation
- Records: Fetching and persistence methods for your custom structs and class hierarchies
- Query Interface: A swift way to generate SQL • create tables, indexes, etc • requests • associations between record types
- Migrations: Transform your database as your application evolves.
- Full-Text Search: Perform efficient and customizable full-text searches.
- Database Observation: Observe database changes and transactions.
- Encryption: Encrypt your database with SQLCipher.
- Backup: Dump the content of a database to another.
- Interrupt a Database: Abort any pending database operation.
- Sharing a Database: How to share an SQLite database between multiple processes - recommendations for App Group containers, App Extensions, App Sandbox, and file coordination.
- Concurrency: How to access databases in a multi-threaded application.
- Combine: Access and observe the database with Combine publishers.
- Avoiding SQL Injection
- Error Handling
- Unicode
- Memory Management
- Data Protection
- 💡 Migrating From GRDB 6 to GRDB 7
- 💡 Why Adopt GRDB?
- 💡 Recommended Practices for Designing Record Types
- GRDBQuery: Access and observe the database from your SwiftUI views.
- GRDBSnapshotTesting: Test your database.
The installation procedures below have GRDB use the version of SQLite that ships with the target operating system.
See Encryption for the installation procedure of GRDB with SQLCipher.
See Custom SQLite builds for the installation procedure of GRDB with a customized build of SQLite.
The Swift Package Manager automates the distribution of Swift code. To use GRDB with SPM, add a dependency to https://github.com/groue/GRDB.swift.git
GRDB offers two libraries, GRDB
and GRDB-dynamic
. Pick only one. When in doubt, prefer GRDB
. The GRDB-dynamic
library can reveal useful if you are going to link it with multiple targets within your app and only wish to link to a shared, dynamic framework once. See How to link a Swift Package as dynamic for more information.
Note: Linux is not currently supported.
CocoaPods is a dependency manager for Xcode projects. To use GRDB with CocoaPods (version 1.2 or higher), specify in your Podfile
:
pod 'GRDB.swift'
GRDB can be installed as a framework, or a static library.
Important Note for CocoaPods installation
Due to an issue in CocoaPods, it is currently not possible to deploy new versions of GRDB to CocoaPods. The last version available on CocoaPods is 6.24.1. To install later versions of GRDB using CocoaPods, use one of the following workarounds:
-
Depend on the
GRDB6
branch. This is more or less equivalent to whatpod 'GRDB.swift', '~> 6.0'
would normally do, if CocoaPods would accept new GRDB versions to be published:# Can't use semantic versioning due to https://github.com/CocoaPods/CocoaPods/issues/11839 pod 'GRDB.swift', git: 'https://github.com/groue/GRDB.swift.git', branch: 'GRDB6'
-
Depend on a specific version explicitly (Replace the tag with the version you want to use):
# Can't use semantic versioning due to https://github.com/CocoaPods/CocoaPods/issues/11839 # Replace the tag with the tag that you want to use. pod 'GRDB.swift', git: 'https://github.com/groue/GRDB.swift.git', tag: 'v6.29.0'
Carthage is unsupported. For some context about this decision, see #433.
-
Download a copy of GRDB, or clone its repository and make sure you checkout the latest tagged version.
-
Embed the
GRDB.xcodeproj
project in your own project. -
Add the
GRDB
target in the Target Dependencies section of the Build Phases tab of your application target (extension target for WatchOS). -
Add the
GRDB.framework
to the Embedded Binaries section of the General tab of your application target (extension target for WatchOS).
GRDB provides two classes for accessing SQLite databases: DatabaseQueue
and DatabasePool
:
import GRDB
// Pick one:
let dbQueue = try DatabaseQueue(path: "/path/to/database.sqlite")
let dbPool = try DatabasePool(path: "/path/to/database.sqlite")
The differences are:
- Database pools allow concurrent database accesses (this can improve the performance of multithreaded applications).
- Database pools open your SQLite database in the WAL mode (unless read-only).
- Database queues support in-memory databases.
If you are not sure, choose DatabaseQueue
. You will always be able to switch to DatabasePool
later.
For more information and tips when opening connections, see Database Connections.
In this section of the documentation, we will talk SQL. Jump to the query interface if SQL is not your cup of tea.
- Executing Updates
- Fetch Queries
- Values
- Data
- Date and DateComponents
- NSNumber, NSDecimalNumber, and Decimal
- Swift enums
DatabaseValueConvertible
: the protocol for custom value types
- Transactions and Savepoints
- SQL Interpolation
Advanced topics:
- Prepared Statements
- Custom SQL Functions and Aggregates
- Database Schema Introspection
- Row Adapters
- Raw SQLite Pointers
Once granted with a database connection, the execute(sql:arguments:)
method executes the SQL statements that do not return any database row, such as CREATE TABLE
, INSERT
, DELETE
, ALTER
, etc.
For example:
try dbQueue.write { db in
try db.execute(sql: """
CREATE TABLE player (
id INTEGER PRIMARY KEY AUTOINCREMENT,
name TEXT NOT NULL,
score INT)
""")
try db.execute(
sql: "INSERT INTO player (name, score) VALUES (?, ?)",
arguments: ["Barbara", 1000])
try db.execute(
sql: "UPDATE player SET score = :score WHERE id = :id",
arguments: ["score": 1000, "id": 1])
}
}
The ?
and colon-prefixed keys like :score
in the SQL query are the statements arguments. You pass arguments with arrays or dictionaries, as in the example above. See Values for more information on supported arguments types (Bool, Int, String, Date, Swift enums, etc.), and StatementArguments
for a detailed documentation of SQLite arguments.
You can also embed query arguments right into your SQL queries, with execute(literal:)
, as in the example below. See SQL Interpolation for more details.
try dbQueue.write { db in
let name = "O'Brien"
let score = 550
try db.execute(literal: """
INSERT INTO player (name, score) VALUES (\(name), \(score))
""")
}
Never ever embed values directly in your raw SQL strings. See Avoiding SQL Injection for more information:
// WRONG: don't embed values in raw SQL strings
let id = 123
let name = textField.text
try db.execute(
sql: "UPDATE player SET name = '\(name)' WHERE id = \(id)")
// CORRECT: use arguments dictionary
try db.execute(
sql: "UPDATE player SET name = :name WHERE id = :id",
arguments: ["name": name, "id": id])
// CORRECT: use arguments array
try db.execute(
sql: "UPDATE player SET name = ? WHERE id = ?",
arguments: [name, id])
// CORRECT: use SQL Interpolation
try db.execute(
literal: "UPDATE player SET name = \(name) WHERE id = \(id)")
Join multiple statements with a semicolon:
try db.execute(sql: """
INSERT INTO player (name, score) VALUES (?, ?);
INSERT INTO player (name, score) VALUES (?, ?);
""", arguments: ["Arthur", 750, "Barbara", 1000])
try db.execute(literal: """
INSERT INTO player (name, score) VALUES (\("Arthur"), \(750));
INSERT INTO player (name, score) VALUES (\("Barbara"), \(1000));
""")
When you want to make sure that a single statement is executed, use a prepared Statement
.
After an INSERT statement, you can get the row ID of the inserted row with lastInsertedRowID
:
try db.execute(
sql: "INSERT INTO player (name, score) VALUES (?, ?)",
arguments: ["Arthur", 1000])
let playerId = db.lastInsertedRowID
Don't miss Records, that provide classic persistence methods:
var player = Player(name: "Arthur", score: 1000)
try player.insert(db)
let playerId = player.id
Database connections let you fetch database rows, plain values, and custom models aka "records".
Rows are the raw results of SQL queries:
try dbQueue.read { db in
if let row = try Row.fetchOne(db, sql: "SELECT * FROM wine WHERE id = ?", arguments: [1]) {
let name: String = row["name"]
let color: Color = row["color"]
print(name, color)
}
}
Values are the Bool, Int, String, Date, Swift enums, etc. stored in row columns:
try dbQueue.read { db in
let urls = try URL.fetchCursor(db, sql: "SELECT url FROM wine")
while let url = try urls.next() {
print(url)
}
}
Records are your application objects that can initialize themselves from rows:
let wines = try dbQueue.read { db in
try Wine.fetchAll(db, sql: "SELECT * FROM wine")
}
Throughout GRDB, you can always fetch cursors, arrays, sets, or single values of any fetchable type (database row, simple value, or custom record):
try Row.fetchCursor(...) // A Cursor of Row
try Row.fetchAll(...) // [Row]
try Row.fetchSet(...) // Set<Row>
try Row.fetchOne(...) // Row?
-
fetchCursor
returns a cursor over fetched values:let rows = try Row.fetchCursor(db, sql: "SELECT ...") // A Cursor of Row
-
fetchAll
returns an array:let players = try Player.fetchAll(db, sql: "SELECT ...") // [Player]
-
fetchSet
returns a set:let names = try String.fetchSet(db, sql: "SELECT ...") // Set<String>
-
fetchOne
returns a single optional value, and consumes a single database row (if any).let count = try Int.fetchOne(db, sql: "SELECT COUNT(*) ...") // Int?
All those fetching methods require an SQL string that contains a single SQL statement. When you want to fetch from multiple statements joined with a semicolon, iterate the multiple prepared statements found in the SQL string.
📖 Cursor
Whenever you consume several rows from the database, you can fetch an Array, a Set, or a Cursor.
The fetchAll()
and fetchSet()
methods return regular Swift array and sets, that you iterate like all other arrays and sets:
try dbQueue.read { db in
// [Player]
let players = try Player.fetchAll(db, sql: "SELECT ...")
for player in players {
// use player
}
}
Unlike arrays and sets, cursors returned by fetchCursor()
load their results step after step:
try dbQueue.read { db in
// Cursor of Player
let players = try Player.fetchCursor(db, sql: "SELECT ...")
while let player = try players.next() {
// use player
}
}
-
Cursors can not be used on any thread: you must consume a cursor on the dispatch queue it was created in. Particularly, don't extract a cursor out of a database access method:
// Wrong let cursor = try dbQueue.read { db in try Player.fetchCursor(db, ...) } while let player = try cursor.next() { ... }
Conversely, arrays and sets may be consumed on any thread:
// OK let array = try dbQueue.read { db in try Player.fetchAll(db, ...) } for player in array { ... }
-
Cursors can be iterated only one time. Arrays and sets can be iterated many times.
-
Cursors iterate database results in a lazy fashion, and don't consume much memory. Arrays and sets contain copies of database values, and may take a lot of memory when there are many fetched results.
-
Cursors are granted with direct access to SQLite, unlike arrays and sets that have to take the time to copy database values. If you look after extra performance, you may prefer cursors.
-
Cursors can feed Swift collections.
You will most of the time use
fetchAll
orfetchSet
when you want an array or a set. For more specific needs, you may prefer one of the initializers below. All of them accept an extra optionalminimumCapacity
argument which helps optimizing your app when you have an idea of the number of elements in a cursor (the built-infetchAll
andfetchSet
do not perform such an optimization).Arrays and all types conforming to
RangeReplaceableCollection
:// [String] let cursor = try String.fetchCursor(db, ...) let array = try Array(cursor)
Sets:
// Set<Int> let cursor = try Int.fetchCursor(db, ...) let set = try Set(cursor)
Dictionaries:
// [Int64: [Player]] let cursor = try Player.fetchCursor(db) let dictionary = try Dictionary(grouping: cursor, by: { $0.teamID }) // [Int64: Player] let cursor = try Player.fetchCursor(db).map { ($0.id, $0) } let dictionary = try Dictionary(uniqueKeysWithValues: cursor)
-
Cursors adopt the Cursor protocol, which looks a lot like standard lazy sequences of Swift. As such, cursors come with many convenience methods:
compactMap
,contains
,dropFirst
,dropLast
,drop(while:)
,enumerated
,filter
,first
,flatMap
,forEach
,joined
,joined(separator:)
,max
,max(by:)
,min
,min(by:)
,map
,prefix
,prefix(while:)
,reduce
,reduce(into:)
,suffix
:// Prints all Github links try URL .fetchCursor(db, sql: "SELECT url FROM link") .filter { url in url.host == "github.com" } .forEach { url in print(url) } // An efficient cursor of coordinates: let locations = try Row. .fetchCursor(db, sql: "SELECT latitude, longitude FROM place") .map { row in CLLocationCoordinate2D(latitude: row[0], longitude: row[1]) }
-
Cursors are not Swift sequences. That's because Swift sequences can't handle iteration errors, when reading SQLite results may fail at any time.
-
Cursors require a little care:
-
Don't modify the results during a cursor iteration:
// Undefined behavior while let player = try players.next() { try db.execute(sql: "DELETE ...") }
-
Don't turn a cursor of
Row
into an array or a set. You would not get the distinct rows you expect. To get a array of rows, useRow.fetchAll(...)
. To get a set of rows, useRow.fetchSet(...)
. Generally speaking, make sure you copy a row whenever you extract it from a cursor for later use:row.copy()
.
-
If you don't see, or don't care about the difference, use arrays. If you care about memory and performance, use cursors when appropriate.
Fetch cursors of rows, arrays, sets, or single rows (see fetching methods):
try dbQueue.read { db in
try Row.fetchCursor(db, sql: "SELECT ...", arguments: ...) // A Cursor of Row
try Row.fetchAll(db, sql: "SELECT ...", arguments: ...) // [Row]
try Row.fetchSet(db, sql: "SELECT ...", arguments: ...) // Set<Row>
try Row.fetchOne(db, sql: "SELECT ...", arguments: ...) // Row?
let rows = try Row.fetchCursor(db, sql: "SELECT * FROM wine")
while let row = try rows.next() {
let name: String = row["name"]
let color: Color = row["color"]
print(name, color)
}
}
let rows = try dbQueue.read { db in
try Row.fetchAll(db, sql: "SELECT * FROM player")
}
Arguments are optional arrays or dictionaries that fill the positional ?
and colon-prefixed keys like :name
in the query:
let rows = try Row.fetchAll(db,
sql: "SELECT * FROM player WHERE name = ?",
arguments: ["Arthur"])
let rows = try Row.fetchAll(db,
sql: "SELECT * FROM player WHERE name = :name",
arguments: ["name": "Arthur"])
See Values for more information on supported arguments types (Bool, Int, String, Date, Swift enums, etc.), and StatementArguments
for a detailed documentation of SQLite arguments.
Unlike row arrays that contain copies of the database rows, row cursors are close to the SQLite metal, and require a little care:
Note: Don't turn a cursor of
Row
into an array or a set. You would not get the distinct rows you expect. To get a array of rows, useRow.fetchAll(...)
. To get a set of rows, useRow.fetchSet(...)
. Generally speaking, make sure you copy a row whenever you extract it from a cursor for later use:row.copy()
.
Read column values by index or column name:
let name: String = row[0] // 0 is the leftmost column
let name: String = row["name"] // Leftmost matching column - lookup is case-insensitive
let name: String = row[Column("name")] // Using query interface's Column
Make sure to ask for an optional when the value may be NULL:
let name: String? = row["name"]
The row[]
subscript returns the type you ask for. See Values for more information on supported value types:
let bookCount: Int = row["bookCount"]
let bookCount64: Int64 = row["bookCount"]
let hasBooks: Bool = row["bookCount"] // false when 0
let string: String = row["date"] // "2015-09-11 18:14:15.123"
let date: Date = row["date"] // Date
self.date = row["date"] // Depends on the type of the property.
You can also use the as
type casting operator:
row[...] as Int
row[...] as Int?
Warning: avoid the
as!
andas?
operators:if let int = row[...] as? Int { ... } // BAD - doesn't work if let int = row[...] as Int? { ... } // GOOD
Warning: avoid nil-coalescing row values, and prefer the
coalesce
method instead:let name: String? = row["nickname"] ?? row["name"] // BAD - doesn't work let name: String? = row.coalesce(["nickname", "name"]) // GOOD
Generally speaking, you can extract the type you need, provided it can be converted from the underlying SQLite value:
-
Successful conversions include:
- All numeric SQLite values to all numeric Swift types, and Bool (zero is the only false boolean).
- Text SQLite values to Swift String.
- Blob SQLite values to Foundation Data.
See Values for more information on supported types (Bool, Int, String, Date, Swift enums, etc.)
-
NULL returns nil.
let row = try Row.fetchOne(db, sql: "SELECT NULL")! row[0] as Int? // nil row[0] as Int // fatal error: could not convert NULL to Int.
There is one exception, though: the DatabaseValue type:
row[0] as DatabaseValue // DatabaseValue.null
-
Missing columns return nil.
let row = try Row.fetchOne(db, sql: "SELECT 'foo' AS foo")! row["missing"] as String? // nil row["missing"] as String // fatal error: no such column: missing
You can explicitly check for a column presence with the
hasColumn
method. -
Invalid conversions throw a fatal error.
let row = try Row.fetchOne(db, sql: "SELECT 'Mom’s birthday'")! row[0] as String // "Mom’s birthday" row[0] as Date? // fatal error: could not convert "Mom’s birthday" to Date. row[0] as Date // fatal error: could not convert "Mom’s birthday" to Date. let row = try Row.fetchOne(db, sql: "SELECT 256")! row[0] as Int // 256 row[0] as UInt8? // fatal error: could not convert 256 to UInt8. row[0] as UInt8 // fatal error: could not convert 256 to UInt8.
Those conversion fatal errors can be avoided with the DatabaseValue type:
let row = try Row.fetchOne(db, sql: "SELECT 'Mom’s birthday'")! let dbValue: DatabaseValue = row[0] if dbValue.isNull { // Handle NULL } else if let date = Date.fromDatabaseValue(dbValue) { // Handle valid date } else { // Handle invalid date }
This extra verbosity is the consequence of having to deal with an untrusted database: you may consider fixing the content of your database instead. See Fatal Errors for more information.
-
SQLite has a weak type system, and provides convenience conversions that can turn String to Int, Double to Blob, etc.
GRDB will sometimes let those conversions go through:
let rows = try Row.fetchCursor(db, sql: "SELECT '20 small cigars'") while let row = try rows.next() { row[0] as Int // 20 }
Don't freak out: those conversions did not prevent SQLite from becoming the immensely successful database engine you want to use. And GRDB adds safety checks described just above. You can also prevent those convenience conversions altogether by using the DatabaseValue type.
DatabaseValue
is an intermediate type between SQLite and your values, which gives information about the raw value stored in the database.
You get DatabaseValue
just like other value types:
let dbValue: DatabaseValue = row[0]
let dbValue: DatabaseValue? = row["name"] // nil if and only if column does not exist
// Check for NULL:
dbValue.isNull // Bool
// The stored value:
dbValue.storage.value // Int64, Double, String, Data, or nil
// All the five storage classes supported by SQLite:
switch dbValue.storage {
case .null: print("NULL")
case .int64(let int64): print("Int64: \(int64)")
case .double(let double): print("Double: \(double)")
case .string(let string): print("String: \(string)")
case .blob(let data): print("Data: \(data)")
}
You can extract regular values (Bool, Int, String, Date, Swift enums, etc.) from DatabaseValue
with the fromDatabaseValue() method:
let dbValue: DatabaseValue = row["bookCount"]
let bookCount = Int.fromDatabaseValue(dbValue) // Int?
let bookCount64 = Int64.fromDatabaseValue(dbValue) // Int64?
let hasBooks = Bool.fromDatabaseValue(dbValue) // Bool?, false when 0
let dbValue: DatabaseValue = row["date"]
let string = String.fromDatabaseValue(dbValue) // "2015-09-11 18:14:15.123"
let date = Date.fromDatabaseValue(dbValue) // Date?
fromDatabaseValue
returns nil for invalid conversions:
let row = try Row.fetchOne(db, sql: "SELECT 'Mom’s birthday'")!
let dbValue: DatabaseValue = row[0]
let string = String.fromDatabaseValue(dbValue) // "Mom’s birthday"
let int = Int.fromDatabaseValue(dbValue) // nil
let date = Date.fromDatabaseValue(dbValue) // nil
Row adopts the standard RandomAccessCollection protocol, and can be seen as a dictionary of DatabaseValue:
// All the (columnName, dbValue) tuples, from left to right:
for (columnName, dbValue) in row {
...
}
You can build rows from dictionaries (standard Swift dictionaries and NSDictionary). See Values for more information on supported types:
let row: Row = ["name": "foo", "date": nil]
let row = Row(["name": "foo", "date": nil])
let row = Row(/* [AnyHashable: Any] */) // nil if invalid dictionary
Yet rows are not real dictionaries: they may contain duplicate columns:
let row = try Row.fetchOne(db, sql: "SELECT 1 AS foo, 2 AS foo")!
row.columnNames // ["foo", "foo"]
row.databaseValues // [1, 2]
row["foo"] // 1 (leftmost matching column)
for (columnName, dbValue) in row { ... } // ("foo", 1), ("foo", 2)
When you build a dictionary from a row, you have to disambiguate identical columns, and choose how to present database values. For example:
-
A
[String: DatabaseValue]
dictionary that keeps leftmost value in case of duplicated column name:let dict = Dictionary(row, uniquingKeysWith: { (left, _) in left })
-
A
[String: AnyObject]
dictionary which keeps rightmost value in case of duplicated column name. This dictionary is identical to FMResultSet's resultDictionary from FMDB. It contains NSNull values for null columns, and can be shared with Objective-C:let dict = Dictionary( row.map { (column, dbValue) in (column, dbValue.storage.value as AnyObject) }, uniquingKeysWith: { (_, right) in right })
-
A
[String: Any]
dictionary that can feed, for example, JSONSerialization:let dict = Dictionary( row.map { (column, dbValue) in (column, dbValue.storage.value) }, uniquingKeysWith: { (left, _) in left })
See the documentation of Dictionary.init(_:uniquingKeysWith:)
for more information.
Instead of rows, you can directly fetch values. There are many supported value types (Bool, Int, String, Date, Swift enums, etc.).
Like rows, fetch values as cursors, arrays, sets, or single values (see fetching methods). Values are extracted from the leftmost column of the SQL queries:
try dbQueue.read { db in
try Int.fetchCursor(db, sql: "SELECT ...", arguments: ...) // A Cursor of Int
try Int.fetchAll(db, sql: "SELECT ...", arguments: ...) // [Int]
try Int.fetchSet(db, sql: "SELECT ...", arguments: ...) // Set<Int>
try Int.fetchOne(db, sql: "SELECT ...", arguments: ...) // Int?
let maxScore = try Int.fetchOne(db, sql: "SELECT MAX(score) FROM player") // Int?
let names = try String.fetchAll(db, sql: "SELECT name FROM player") // [String]
}
Int.fetchOne
returns nil in two cases: either the SELECT statement yielded no row, or one row with a NULL value:
// No row:
try Int.fetchOne(db, sql: "SELECT 42 WHERE FALSE") // nil
// One row with a NULL value:
try Int.fetchOne(db, sql: "SELECT NULL") // nil
// One row with a non-NULL value:
try Int.fetchOne(db, sql: "SELECT 42") // 42
For requests which may contain NULL, fetch optionals:
try dbQueue.read { db in
try Optional<Int>.fetchCursor(db, sql: "SELECT ...", arguments: ...) // A Cursor of Int?
try Optional<Int>.fetchAll(db, sql: "SELECT ...", arguments: ...) // [Int?]
try Optional<Int>.fetchSet(db, sql: "SELECT ...", arguments: ...) // Set<Int?>
}
💡 Tip: One advanced use case, when you fetch one value, is to distinguish the cases of a statement that yields no row, or one row with a NULL value. To do so, use
Optional<Int>.fetchOne
, which returns a double optionalInt??
:// No row: try Optional<Int>.fetchOne(db, sql: "SELECT 42 WHERE FALSE") // .none // One row with a NULL value: try Optional<Int>.fetchOne(db, sql: "SELECT NULL") // .some(.none) // One row with a non-NULL value: try Optional<Int>.fetchOne(db, sql: "SELECT 42") // .some(.some(42))
There are many supported value types (Bool, Int, String, Date, Swift enums, etc.). See Values for more information.
GRDB ships with built-in support for the following value types:
-
Swift Standard Library: Bool, Double, Float, all signed and unsigned integer types, String, Swift enums.
-
Foundation: Data, Date, DateComponents, Decimal, NSNull, NSNumber, NSString, URL, UUID.
-
CoreGraphics: CGFloat.
-
DatabaseValue, the type which gives information about the raw value stored in the database.
-
Full-Text Patterns: FTS3Pattern and FTS5Pattern.
-
Generally speaking, all types that adopt the
DatabaseValueConvertible
protocol.
Values can be used as statement arguments:
let url: URL = ...
let verified: Bool = ...
try db.execute(
sql: "INSERT INTO link (url, verified) VALUES (?, ?)",
arguments: [url, verified])
Values can be extracted from rows:
let rows = try Row.fetchCursor(db, sql: "SELECT * FROM link")
while let row = try rows.next() {
let url: URL = row["url"]
let verified: Bool = row["verified"]
}
Values can be directly fetched:
let urls = try URL.fetchAll(db, sql: "SELECT url FROM link") // [URL]
Use values in Records:
struct Link: FetchableRecord {
var url: URL
var isVerified: Bool
init(row: Row) {
url = row["url"]
isVerified = row["verified"]
}
}
Use values in the query interface:
let url: URL = ...
let link = try Link.filter(Column("url") == url).fetchOne(db)
Data suits the BLOB SQLite columns. It can be stored and fetched from the database just like other values:
let rows = try Row.fetchCursor(db, sql: "SELECT data, ...")
while let row = try rows.next() {
let data: Data = row["data"]
}
At each step of the request iteration, the row[]
subscript creates two copies of the database bytes: one fetched by SQLite, and another, stored in the Swift Data value.
You have the opportunity to save memory by not copying the data fetched by SQLite:
while let row = try rows.next() {
try row.withUnsafeData(name: "data") { (data: Data?) in
...
}
}
The non-copied data does not live longer than the iteration step: make sure that you do not use it past this point.
Date and DateComponents can be stored and fetched from the database.
Here is how GRDB supports the various date formats supported by SQLite:
SQLite format | Date | DateComponents |
---|---|---|
YYYY-MM-DD | Read ¹ | Read / Write |
YYYY-MM-DD HH:MM | Read ¹ ² | Read ² / Write |
YYYY-MM-DD HH:MM:SS | Read ¹ ² | Read ² / Write |
YYYY-MM-DD HH:MM:SS.SSS | Read ¹ ² / Write ¹ | Read ² / Write |
YYYY-MM-DDTHH:MM | Read ¹ ² | Read ² |
YYYY-MM-DDTHH:MM:SS | Read ¹ ² | Read ² |
YYYY-MM-DDTHH:MM:SS.SSS | Read ¹ ² | Read ² |
HH:MM | Read ² / Write | |
HH:MM:SS | Read ² / Write | |
HH:MM:SS.SSS | Read ² / Write | |
Timestamps since unix epoch | Read ³ | |
now |
¹ Missing components are assumed to be zero. Dates are stored and read in the UTC time zone, unless the format is followed by a timezone indicator ⁽²⁾.
² This format may be optionally followed by a timezone indicator of the form [+-]HH:MM
or just Z
.
³ GRDB 2+ interprets numerical values as timestamps that fuel Date(timeIntervalSince1970:)
. Previous GRDB versions used to interpret numbers as julian days. Julian days are still supported, with the Date(julianDay:)
initializer.
Warning: the range of valid years in the SQLite date formats is 0000-9999. You will need to pick another date format when your application needs to process years outside of this range. See the following chapters.
Date can be stored and fetched from the database just like other values:
try db.execute(
sql: "INSERT INTO player (creationDate, ...) VALUES (?, ...)",
arguments: [Date(), ...])
let row = try Row.fetchOne(db, ...)!
let creationDate: Date = row["creationDate"]
Dates are stored using the format "YYYY-MM-DD HH:MM:SS.SSS" in the UTC time zone. It is precise to the millisecond.
Note: this format was chosen because it is the only format that is:
- Comparable (
ORDER BY date
works)- Comparable with the SQLite keyword CURRENT_TIMESTAMP (
WHERE date > CURRENT_TIMESTAMP
works)- Able to feed SQLite date & time functions
- Precise enough
Warning: the range of valid years in the SQLite date format is 0000-9999. You will experience problems with years outside of this range, such as decoding errors, or invalid date computations with SQLite date & time functions.
Some applications may prefer another date format:
- Some may prefer ISO-8601, with a
T
separator. - Some may prefer ISO-8601, with a time zone.
- Some may need to store years beyond the 0000-9999 range.
- Some may need sub-millisecond precision.
- Some may need exact
Date
roundtrip. - Etc.
You should think twice before choosing a different date format:
- ISO-8601 is about exchange and communication, when SQLite is about storage and data manipulation. Sharing the same representation in your database and in JSON files only provides a superficial convenience, and should be the least of your priorities. Don't store dates as ISO-8601 without understanding what you lose. For example, ISO-8601 time zones forbid database-level date comparison.
- Sub-millisecond precision and exact
Date
roundtrip are not as obvious needs as it seems at first sight. Dates generally don't precisely roundtrip as soon as they leave your application anyway, because the other systems your app communicates with use their own date representation (the Android version of your app, the server your application is talking to, etc.) On top of that,Date
comparison is at least as hard and nasty as floating point comparison.
The customization of date format is explicit. For example:
let date = Date()
let timeInterval = date.timeIntervalSinceReferenceDate
try db.execute(
sql: "INSERT INTO player (creationDate, ...) VALUES (?, ...)",
arguments: [timeInterval, ...])
if let row = try Row.fetchOne(db, ...) {
let timeInterval: TimeInterval = row["creationDate"]
let creationDate = Date(timeIntervalSinceReferenceDate: timeInterval)
}
See also Codable Records for more date customization options, and DatabaseValueConvertible
if you want to define a Date-wrapping type with customized database representation.
DateComponents is indirectly supported, through the DatabaseDateComponents helper type.
DatabaseDateComponents reads date components from all date formats supported by SQLite, and stores them in the format of your choice, from HH:MM to YYYY-MM-DD HH:MM:SS.SSS.
Warning: the range of valid years is 0000-9999. You will experience problems with years outside of this range, such as decoding errors, or invalid date computations with SQLite date & time functions. See Date for more information.
DatabaseDateComponents can be stored and fetched from the database just like other values:
let components = DateComponents()
components.year = 1973
components.month = 9
components.day = 18
// Store "1973-09-18"
let dbComponents = DatabaseDateComponents(components, format: .YMD)
try db.execute(
sql: "INSERT INTO player (birthDate, ...) VALUES (?, ...)",
arguments: [dbComponents, ...])
// Read "1973-09-18"
let row = try Row.fetchOne(db, sql: "SELECT birthDate ...")!
let dbComponents: DatabaseDateComponents = row["birthDate"]
dbComponents.format // .YMD (the actual format found in the database)
dbComponents.dateComponents // DateComponents
NSNumber and Decimal can be stored and fetched from the database just like other values.
Here is how GRDB supports the various data types supported by SQLite:
Integer | Double | String | |
---|---|---|---|
NSNumber | Read / Write | Read / Write | Read |
NSDecimalNumber | Read / Write | Read / Write | Read |
Decimal | Read | Read | Read / Write |
-
All three types can decode database integers and doubles:
let number = try NSNumber.fetchOne(db, sql: "SELECT 10") // NSNumber let number = try NSDecimalNumber.fetchOne(db, sql: "SELECT 1.23") // NSDecimalNumber let number = try Decimal.fetchOne(db, sql: "SELECT -100") // Decimal
-
All three types decode database strings as decimal numbers:
let number = try NSNumber.fetchOne(db, sql: "SELECT '10'") // NSDecimalNumber (sic) let number = try NSDecimalNumber.fetchOne(db, sql: "SELECT '1.23'") // NSDecimalNumber let number = try Decimal.fetchOne(db, sql: "SELECT '-100'") // Decimal
-
NSNumber
andNSDecimalNumber
send 64-bit signed integers and doubles in the database:// INSERT INTO transfer VALUES (10) try db.execute(sql: "INSERT INTO transfer VALUES (?)", arguments: [NSNumber(value: 10)]) // INSERT INTO transfer VALUES (10.0) try db.execute(sql: "INSERT INTO transfer VALUES (?)", arguments: [NSNumber(value: 10.0)]) // INSERT INTO transfer VALUES (10) try db.execute(sql: "INSERT INTO transfer VALUES (?)", arguments: [NSDecimalNumber(string: "10.0")]) // INSERT INTO transfer VALUES (10.5) try db.execute(sql: "INSERT INTO transfer VALUES (?)", arguments: [NSDecimalNumber(string: "10.5")])
Warning: since SQLite does not support decimal numbers, sending a non-integer
NSDecimalNumber
can result in a loss of precision during the conversion to double.Instead of sending non-integer
NSDecimalNumber
to the database, you may prefer:- Send
Decimal
instead (those store decimal strings in the database). - Send integers instead (for example, store amounts of cents instead of amounts of Euros).
- Send
-
Decimal
sends decimal strings in the database:// INSERT INTO transfer VALUES ('10') try db.execute(sql: "INSERT INTO transfer VALUES (?)", arguments: [Decimal(10)]) // INSERT INTO transfer VALUES ('10.5') try db.execute(sql: "INSERT INTO transfer VALUES (?)", arguments: [Decimal(string: "10.5")!])
UUID can be stored and fetched from the database just like other values.
GRDB stores uuids as 16-bytes data blobs, and decodes them from both 16-bytes data blobs and strings such as "E621E1F8-C36C-495A-93FC-0C247A3E6E5F".
Swift enums and generally all types that adopt the RawRepresentable protocol can be stored and fetched from the database just like their raw values:
enum Color : Int {
case red, white, rose
}
enum Grape : String {
case chardonnay, merlot, riesling
}
// Declare empty DatabaseValueConvertible adoption
extension Color : DatabaseValueConvertible { }
extension Grape : DatabaseValueConvertible { }
// Store
try db.execute(
sql: "INSERT INTO wine (grape, color) VALUES (?, ?)",
arguments: [Grape.merlot, Color.red])
// Read
let rows = try Row.fetchCursor(db, sql: "SELECT * FROM wine")
while let row = try rows.next() {
let grape: Grape = row["grape"]
let color: Color = row["color"]
}
When a database value does not match any enum case, you get a fatal error. This fatal error can be avoided with the DatabaseValue type:
let row = try Row.fetchOne(db, sql: "SELECT 'syrah'")!
row[0] as String // "syrah"
row[0] as Grape? // fatal error: could not convert "syrah" to Grape.
row[0] as Grape // fatal error: could not convert "syrah" to Grape.
let dbValue: DatabaseValue = row[0]
if dbValue.isNull {
// Handle NULL
} else if let grape = Grape.fromDatabaseValue(dbValue) {
// Handle valid grape
} else {
// Handle unknown grape
}
SQLite lets you define SQL functions and aggregates.
A custom SQL function or aggregate extends SQLite:
SELECT reverse(name) FROM player; -- custom function
SELECT maxLength(name) FROM player; -- custom aggregate
A function argument takes an array of DatabaseValue, and returns any valid value (Bool, Int, String, Date, Swift enums, etc.) The number of database values is guaranteed to be argumentCount.
SQLite has the opportunity to perform additional optimizations when functions are "pure", which means that their result only depends on their arguments. So make sure to set the pure argument to true when possible.
let reverse = DatabaseFunction("reverse", argumentCount: 1, pure: true) { (values: [DatabaseValue]) in
// Extract string value, if any...
guard let string = String.fromDatabaseValue(values[0]) else {
return nil
}
// ... and return reversed string:
return String(string.reversed())
}
You make a function available to a database connection through its configuration:
var config = Configuration()
config.prepareDatabase { db in
db.add(function: reverse)
}
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config)
try dbQueue.read { db in
// "oof"
try String.fetchOne(db, sql: "SELECT reverse('foo')")!
}
Functions can take a variable number of arguments:
When you don't provide any explicit argumentCount, the function can take any number of arguments:
let averageOf = DatabaseFunction("averageOf", pure: true) { (values: [DatabaseValue]) in
let doubles = values.compactMap { Double.fromDatabaseValue($0) }
return doubles.reduce(0, +) / Double(doubles.count)
}
db.add(function: averageOf)
// 2.0
try Double.fetchOne(db, sql: "SELECT averageOf(1, 2, 3)")!
Functions can throw:
let sqrt = DatabaseFunction("sqrt", argumentCount: 1, pure: true) { (values: [DatabaseValue]) in
guard let double = Double.fromDatabaseValue(values[0]) else {
return nil
}
guard double >= 0 else {
throw DatabaseError(message: "invalid negative number")
}
return sqrt(double)
}
db.add(function: sqrt)
// SQLite error 1 with statement `SELECT sqrt(-1)`: invalid negative number
try Double.fetchOne(db, sql: "SELECT sqrt(-1)")!
Use custom functions in the query interface:
// SELECT reverseString("name") FROM player
Player.select(reverseString(nameColumn))
GRDB ships with built-in SQL functions that perform unicode-aware string transformations. See Unicode.
📖 DatabaseFunction
, DatabaseAggregate
Before registering a custom aggregate, you need to define a type that adopts the DatabaseAggregate
protocol:
protocol DatabaseAggregate {
// Initializes an aggregate
init()
// Called at each step of the aggregation
mutating func step(_ dbValues: [DatabaseValue]) throws
// Returns the final result
func finalize() throws -> DatabaseValueConvertible?
}
For example:
struct MaxLength : DatabaseAggregate {
var maxLength: Int = 0
mutating func step(_ dbValues: [DatabaseValue]) {
// At each step, extract string value, if any...
guard let string = String.fromDatabaseValue(dbValues[0]) else {
return
}
// ... and update the result
let length = string.count
if length > maxLength {
maxLength = length
}
}
func finalize() -> DatabaseValueConvertible? {
maxLength
}
}
let maxLength = DatabaseFunction(
"maxLength",
argumentCount: 1,
pure: true,
aggregate: MaxLength.self)
Like custom SQL Functions, you make an aggregate function available to a database connection through its configuration:
var config = Configuration()
config.prepareDatabase { db in
db.add(function: maxLength)
}
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config)
try dbQueue.read { db in
// Some Int
try Int.fetchOne(db, sql: "SELECT maxLength(name) FROM player")!
}
The step
method of the aggregate takes an array of DatabaseValue. This array contains as many values as the argumentCount parameter (or any number of values, when argumentCount is omitted).
The finalize
method of the aggregate returns the final aggregated value (Bool, Int, String, Date, Swift enums, etc.).
SQLite has the opportunity to perform additional optimizations when aggregates are "pure", which means that their result only depends on their inputs. So make sure to set the pure argument to true when possible.
Use custom aggregates in the query interface:
// SELECT maxLength("name") FROM player
let request = Player.select(maxLength.apply(nameColumn))
try Int.fetchOne(db, request) // Int?
If not all SQLite APIs are exposed in GRDB, you can still use the SQLite C Interface and call SQLite C functions.
To access the C SQLite functions from SQLCipher or the system SQLite, you need to perform an extra import:
import SQLite3 // System SQLite
import SQLCipher // SQLCipher
let sqliteVersion = String(cString: sqlite3_libversion())
Raw pointers to database connections and statements are available through the Database.sqliteConnection
and Statement.sqliteStatement
properties:
try dbQueue.read { db in
// The raw pointer to a database connection:
let sqliteConnection = db.sqliteConnection
// The raw pointer to a statement:
let statement = try db.makeStatement(sql: "SELECT ...")
let sqliteStatement = statement.sqliteStatement
}
Note
- Those pointers are owned by GRDB: don't close connections or finalize statements created by GRDB.
- GRDB opens SQLite connections in the "multi-thread mode", which (oddly) means that they are not thread-safe. Make sure you touch raw databases and statements inside their dedicated dispatch queues.
- Use the raw SQLite C Interface at your own risk. GRDB won't prevent you from shooting yourself in the foot.
On top of the SQLite API, GRDB provides protocols that help manipulating database rows as regular objects named "records":
try dbQueue.write { db in
if var place = try Place.fetchOne(db, id: 1) {
place.isFavorite = true
try place.update(db)
}
}
Of course, you need to open a database connection, and create database tables first.
To define a record type, define a type and extend it with protocols that come with focused sets of features.
For example:
struct Player: {
var id: Int64
var name: String
var score: Int
}
// Players can be fetched from the database.
extension Player: FetchableRecord { ... }
// Players can be saved into the database.
extension Player: PersistableRecord { ... }
See some examples of record definitions.
Note: if you are familiar with Core Data's NSManagedObject or Realm's Object, you may experience a cultural shock: GRDB records are not uniqued, do not auto-update, and do not lazy-load. This is both a purpose, and a consequence of protocol-oriented programming.
Tip: The Recommended Practices for Designing Record Types guide provides general guidance..
Tip: See the Demo Applications for sample apps that uses records.
Overview
Protocols and the Record Class
- Record Protocols Overview
- FetchableRecord Protocol
- TableRecord Protocol
- PersistableRecord Protocol
- Identifiable Records
- Codable Records
- Record Comparison
- Record Customization Options
- Record Timestamps and Transaction Date
To insert a record in the database, call the insert
method:
let player = Player(name: "Arthur", email: "[email protected]")
try player.insert(db)
👉 insert
is available for types that adopt the PersistableRecord protocol.
To fetch records from the database, call a fetching method:
let arthur = try Player.fetchOne(db, // Player?
sql: "SELECT * FROM players WHERE name = ?",
arguments: ["Arthur"])
let bestPlayers = try Player // [Player]
.order(Column("score").desc)
.limit(10)
.fetchAll(db)
let spain = try Country.fetchOne(db, id: "ES") // Country?
let italy = try Country.find(db, id: "IT") // Country
👉 Fetching from raw SQL is available for types that adopt the FetchableRecord protocol.
👉 Fetching without SQL, using the query interface, is available for types that adopt both FetchableRecord and TableRecord protocol.
To update a record in the database, call the update
method:
var player: Player = ...
player.score = 1000
try player.update(db)
It is possible to avoid useless updates:
// does not hit the database if score has not changed
try player.updateChanges(db) {
$0.score = 1000
}
See the query interface for batch updates:
try Player
.filter(Column("team") == "red")
.updateAll(db, Column("score") += 1)
👉 update methods are available for types that adopt the PersistableRecord protocol. Batch updates are available on the TableRecord protocol.
To delete a record in the database, call the delete
method:
let player: Player = ...
try player.delete(db)
You can also delete by primary key, unique key, or perform batch deletes (see Delete Requests):
try Player.deleteOne(db, id: 1)
try Player.deleteOne(db, key: ["email": "[email protected]"])
try Country.deleteAll(db, ids: ["FR", "US"])
try Player
.filter(Column("email") == nil)
.deleteAll(db)
👉 delete methods are available for types that adopt the PersistableRecord protocol. Batch deletes are available on the TableRecord protocol.
To count records, call the fetchCount
method:
let playerCount: Int = try Player.fetchCount(db)
let playerWithEmailCount: Int = try Player
.filter(Column("email") == nil)
.fetchCount(db)
👉 fetchCount
is available for types that adopt the TableRecord protocol.
Details follow:
- Record Protocols Overview
- FetchableRecord Protocol
- TableRecord Protocol
- PersistableRecord Protocol
- Identifiable Records
- Codable Records
- Record Comparison
- Record Customization Options
- Examples of Record Definitions
GRDB ships with three record protocols. Your own types will adopt one or several of them, according to the abilities you want to extend your types with.
-
FetchableRecord is able to decode database rows.
struct Place: FetchableRecord { ... } let places = try dbQueue.read { db in try Place.fetchAll(db, sql: "SELECT * FROM place") }
💡 Tip:
FetchableRecord
can derive its implementation from the standardDecodable
protocol. See Codable Records for more information.FetchableRecord
can decode database rows, but it is not able to build SQL requests for you. For that, you also needTableRecord
: -
TableRecord is able to generate SQL queries:
struct Place: TableRecord { ... } let placeCount = try dbQueue.read { db in // Generates and runs `SELECT COUNT(*) FROM place` try Place.fetchCount(db) }
When a type adopts both
TableRecord
andFetchableRecord
, it can load from those requests:struct Place: TableRecord, FetchableRecord { ... } try dbQueue.read { db in let places = try Place.order(Column("title")).fetchAll(db) let paris = try Place.fetchOne(id: 1) }
-
PersistableRecord is able to write: it can create, update, and delete rows in the database:
struct Place : PersistableRecord { ... } try dbQueue.write { db in try Place.delete(db, id: 1) try Place(...).insert(db) }
A persistable record can also compare itself against other records, and avoid useless database updates.
💡 Tip:
PersistableRecord
can derive its implementation from the standardEncodable
protocol. See Codable Records for more information.
The FetchableRecord protocol grants fetching methods to any type that can be built from a database row:
protocol FetchableRecord {
/// Row initializer
init(row: Row) throws
}
For example:
struct Place {
var id: Int64?
var title: String
var coordinate: CLLocationCoordinate2D
}
extension Place : FetchableRecord {
init(row: Row) {
id = row["id"]
title = row["title"]
coordinate = CLLocationCoordinate2D(
latitude: row["latitude"],
longitude: row["longitude"])
}
}
Rows also accept column enums:
extension Place : FetchableRecord {
enum Columns: String, ColumnExpression {
case id, title, latitude, longitude
}
init(row: Row) {
id = row[Columns.id]
title = row[Columns.title]
coordinate = CLLocationCoordinate2D(
latitude: row[Columns.latitude],
longitude: row[Columns.longitude])
}
}
See column values for more information about the row[]
subscript.
When your record type adopts the standard Decodable protocol, you don't have to provide the implementation for init(row:)
. See Codable Records for more information:
// That's all
struct Player: Decodable, FetchableRecord {
var id: Int64
var name: String
var score: Int
}
FetchableRecord allows adopting types to be fetched from SQL queries:
try Place.fetchCursor(db, sql: "SELECT ...", arguments:...) // A Cursor of Place
try Place.fetchAll(db, sql: "SELECT ...", arguments:...) // [Place]
try Place.fetchSet(db, sql: "SELECT ...", arguments:...) // Set<Place>
try Place.fetchOne(db, sql: "SELECT ...", arguments:...) // Place?
See fetching methods for information about the fetchCursor
, fetchAll
, fetchSet
and fetchOne
methods. See StatementArguments
for more information about the query arguments.
Note: for performance reasons, the same row argument to
init(row:)
is reused during the iteration of a fetch query. If you want to keep the row for later use, make sure to store a copy:self.row = row.copy()
.
Note: The
FetchableRecord.init(row:)
initializer fits the needs of most applications. But some application are more demanding than others. When FetchableRecord does not exactly provide the support you need, have a look at the Beyond FetchableRecord chapter.
The TableRecord protocol generates SQL for you:
protocol TableRecord {
static var databaseTableName: String { get }
static var databaseSelection: [any SQLSelectable] { get }
}
The databaseSelection
type property is optional, and documented in the Columns Selected by a Request chapter.
The databaseTableName
type property is the name of a database table. By default, it is derived from the type name:
struct Place: TableRecord { }
print(Place.databaseTableName) // prints "place"
For example:
- Place:
place
- Country:
country
- PostalAddress:
postalAddress
- HTTPRequest:
httpRequest
- TOEFL:
toefl
You can still provide a custom table name:
struct Place: TableRecord {
static let databaseTableName = "location"
}
print(Place.databaseTableName) // prints "location"
When a type adopts both TableRecord and FetchableRecord, it can be fetched using the query interface:
// SELECT * FROM place WHERE name = 'Paris'
let paris = try Place.filter(nameColumn == "Paris").fetchOne(db)
TableRecord can also fetch deal with primary and unique keys: see Fetching by Key and Testing for Record Existence.
📖 EncodableRecord
, MutablePersistableRecord
, PersistableRecord
GRDB record types can create, update, and delete rows in the database.
Those abilities are granted by three protocols:
// Defines how a record encodes itself into the database
protocol EncodableRecord {
/// Defines the values persisted in the database
func encode(to container: inout PersistenceContainer) throws
}
// Adds persistence methods
protocol MutablePersistableRecord: TableRecord, EncodableRecord {
/// Optional method that lets your adopting type store its rowID upon
/// successful insertion. Don't call it directly: it is called for you.
mutating func didInsert(_ inserted: InsertionSuccess)
}
// Adds immutability
protocol PersistableRecord: MutablePersistableRecord {
/// Non-mutating version of the optional didInsert(_:)
func didInsert(_ inserted: InsertionSuccess)
}
Yes, three protocols instead of one. Here is how you pick one or the other:
-
If your type is a class, choose
PersistableRecord
. On top of that, implementdidInsert(_:)
if the database table has an auto-incremented primary key. -
If your type is a struct, and the database table has an auto-incremented primary key, choose
MutablePersistableRecord
, and implementdidInsert(_:)
. -
Otherwise, choose
PersistableRecord
, and ignoredidInsert(_:)
.
The encode(to:)
method defines which values (Bool, Int, String, Date, Swift enums, etc.) are assigned to database columns.
The optional didInsert
method lets the adopting type store its rowID after successful insertion, and is only useful for tables that have an auto-incremented primary key. It is called from a protected dispatch queue, and serialized with all database updates.
For example:
extension Place : MutablePersistableRecord {
/// The values persisted in the database
func encode(to container: inout PersistenceContainer) {
container["id"] = id
container["title"] = title
container["latitude"] = coordinate.latitude
container["longitude"] = coordinate.longitude
}
// Update auto-incremented id upon successful insertion
mutating func didInsert(_ inserted: InsertionSuccess) {
id = inserted.rowID
}
}
var paris = Place(
id: nil,
title: "Paris",
coordinate: CLLocationCoordinate2D(latitude: 48.8534100, longitude: 2.3488000))
try paris.insert(db)
paris.id // some value
Persistence containers also accept column enums:
extension Place : MutablePersistableRecord {
enum Columns: String, ColumnExpression {
case id, title, latitude, longitude
}
func encode(to container: inout PersistenceContainer) {
container[Columns.id] = id
container[Columns.title] = title
container[Columns.latitude] = coordinate.latitude
container[Columns.longitude] = coordinate.longitude
}
}
When your record type adopts the standard Encodable protocol, you don't have to provide the implementation for encode(to:)
. See Codable Records for more information:
// That's all
struct Player: Encodable, MutablePersistableRecord {
var id: Int64?
var name: String
var score: Int
// Update auto-incremented id upon successful insertion
mutating func didInsert(_ inserted: InsertionSuccess) {
id = inserted.rowID
}
}
Types that adopt the PersistableRecord protocol are given methods that insert, update, and delete:
// INSERT
try place.insert(db)
let insertedPlace = try place.inserted(db) // non-mutating
// UPDATE
try place.update(db)
try place.update(db, columns: ["title"])
// Maybe UPDATE
try place.updateChanges(db, from: otherPlace)
try place.updateChanges(db) { $0.isFavorite = true }
// INSERT or UPDATE
try place.save(db)
let savedPlace = place.saved(db) // non-mutating
// UPSERT
try place.upsert(db)
let insertedPlace = place.upsertAndFetch(db)
// DELETE
try place.delete(db)
// EXISTENCE CHECK
let exists = try place.exists(db)
See Upsert below for more information about upserts.
The TableRecord protocol comes with batch operations:
// UPDATE
try Place.updateAll(db, ...)
// DELETE
try Place.deleteAll(db)
try Place.deleteAll(db, ids:...)
try Place.deleteAll(db, keys:...)
try Place.deleteOne(db, id:...)
try Place.deleteOne(db, key:...)
For more information about batch updates, see Update Requests.
-
All persistence methods can throw a DatabaseError.
-
update
andupdateChanges
throw RecordError if the database does not contain any row for the primary key of the record. -
save
makes sure your values are stored in the database. It performs an UPDATE if the record has a non-null primary key, and then, if no row was modified, an INSERT. It directly performs an INSERT if the record has no primary key, or a null primary key. -
delete
anddeleteOne
returns whether a database row was deleted or not.deleteAll
returns the number of deleted rows.updateAll
returns the number of updated rows.updateChanges
returns whether a database row was updated or not.
All primary keys are supported, including composite primary keys that span several columns, and the hidden rowid
column.
To customize persistence methods, you provide Persistence Callbacks, described below. Do not attempt at overriding the ready-made persistence methods.
UPSERT is an SQLite feature that causes an INSERT to behave as an UPDATE or a no-op if the INSERT would violate a uniqueness constraint (primary key or unique index).
Note: Upsert apis are available from SQLite 3.35.0+: iOS 15.0+, macOS 12.0+, tvOS 15.0+, watchOS 8.0+, or with a custom SQLite build or SQLCipher.
Note: With regard to persistence callbacks, an upsert behaves exactly like an insert. In particular: the
aroundInsert(_:)
anddidInsert(_:)
callbacks reports the rowid of the inserted or updated row;willUpdate
,aroundUdate
,didUdate
are not called.
PersistableRecord provides three upsert methods:
-
upsert(_:)
Inserts or updates a record.
The upsert behavior is triggered by a violation of any uniqueness constraint on the table (primary key or unique index). In case of conflict, all columns but the primary key are overwritten with the inserted values:
struct Player: Encodable, PersistableRecord { var id: Int64 var name: String var score: Int } // INSERT INTO player (id, name, score) // VALUES (1, 'Arthur', 1000) // ON CONFLICT DO UPDATE SET // name = excluded.name, // score = excluded.score let player = Player(id: 1, name: "Arthur", score: 1000) try player.upsert(db)
-
upsertAndFetch(_:onConflict:doUpdate:)
(requires FetchableRecord conformance)Inserts or updates a record, and returns the upserted record.
The
onConflict
anddoUpdate
arguments let you further control the upsert behavior. Make sure you check the SQLite UPSERT documentation for detailed information.-
onConflict
: the "conflict target" is the array of columns in the uniqueness constraint (primary key or unique index) that triggers the upsert.If empty (the default), all uniqueness constraint are considered.
-
doUpdate
: a closure that returns columns assignments to perform in case of conflict. Other columns are overwritten with the inserted values.By default, all inserted columns but the primary key and the conflict target are overwritten.
In the example below, we upsert the new vocabulary word "jovial". It is inserted if that word is not already in the dictionary. Otherwise,
count
is incremented,isTainted
is not overwritten, andkind
is overwritten:// CREATE TABLE vocabulary( // word TEXT NOT NULL PRIMARY KEY, // kind TEXT NOT NULL, // isTainted BOOLEAN DEFAULT 0, // count INT DEFAULT 1)) struct Vocabulary: Encodable, PersistableRecord { var word: String var kind: String var isTainted: Bool } // INSERT INTO vocabulary(word, kind, isTainted) // VALUES('jovial', 'adjective', 0) // ON CONFLICT(word) DO UPDATE SET \ // count = count + 1, -- on conflict, count is incremented // kind = excluded.kind -- on conflict, kind is overwritten // RETURNING * let vocabulary = Vocabulary(word: "jovial", kind: "adjective", isTainted: false) let upserted = try vocabulary.upsertAndFetch( db, onConflict: ["word"], doUpdate: { _ in [Column("count") += 1, // on conflict, count is incremented Column("isTainted").noOverwrite] // on conflict, isTainted is NOT overwritten })
The
doUpdate
closure accepts anexcluded
TableAlias argument that refers to the inserted values that trigger the conflict. You can use it to specify an explicit overwrite, or to perform a computation. In the next example, the upsert keeps the maximum date in case of conflict:// INSERT INTO message(id, text, date) // VALUES(...) // ON CONFLICT DO UPDATE SET \ // text = excluded.text, // date = MAX(date, excluded.date) // RETURNING * let upserted = try message.upsertAndFetch(doUpdate: { excluded in // keep the maximum date in case of conflict [Column("date").set(to: max(Column("date"), excluded["date"]))] })
-
-
upsertAndFetch(_:as:onConflict:doUpdate:)
(does not require FetchableRecord conformance)This method is identical to
upsertAndFetch(_:onConflict:doUpdate:)
described above, but you can provide a distinct FetchableRecord record type as a result, in order to specify the returned columns.
SQLite is able to return values from a inserted, updated, or deleted row, with the RETURNING
clause.
Note: Support for the
RETURNING
clause is available from SQLite 3.35.0+: iOS 15.0+, macOS 12.0+, tvOS 15.0+, watchOS 8.0+, or with a custom SQLite build or SQLCipher.
The RETURNING
clause helps dealing with database features such as auto-incremented ids, default values, and generated columns. You can, for example, insert a few columns and fetch the default or generated ones in one step.
GRDB uses the RETURNING
clause in all persistence methods that contain AndFetch
in their name.
For example, given a database table with an auto-incremented primary key and a default score:
try dbQueue.write { db in
try db.execute(sql: """
CREATE TABLE player(
id INTEGER PRIMARY KEY AUTOINCREMENT,
name TEXT NOT NULL,
score INTEGER NOT NULL DEFAULT 1000)
""")
}
You can define a record type with full database information, and another partial record type that deals with a subset of columns:
// A player with full database information
struct Player: Codable, PersistableRecord, FetchableRecord {
var id: Int64
var name: String
var score: Int
}
// A partial player
struct PartialPlayer: Encodable, PersistableRecord {
static let databaseTableName = "player"
var name: String
}
And now you can get a full player by inserting a partial one:
try dbQueue.write { db in
let partialPlayer = PartialPlayer(name: "Alice")
// INSERT INTO player (name) VALUES ('Alice') RETURNING *
let player = try partialPlayer.insertAndFetch(db, as: Player.self)
print(player.id) // The inserted id
print(player.name) // The inserted name
print(player.score) // The default score
}
For extra precision, you can select only the columns you need, and fetch the desired value from the provided prepared Statement
:
try dbQueue.write { db in
let partialPlayer = PartialPlayer(name: "Alice")
// INSERT INTO player (name) VALUES ('Alice') RETURNING score
let score = try partialPlayer.insertAndFetch(db, selection: [Column("score")]) { statement in
try Int.fetchOne(statement)
}
print(score) // Prints 1000, the default score
}
There are other similar persistence methods, such as upsertAndFetch
, saveAndFetch
, updateAndFetch
, updateChangesAndFetch
, etc. They all behave like upsert
, save
, update
, updateChanges
, except that they return saved values. For example:
// Save and return the saved player
let savedPlayer = try player.saveAndFetch(db)
See Persistence Methods, Upsert, and updateChanges
methods for more information.
Batch operations can return updated or deleted values:
Warning: Make sure you check the documentation of the
RETURNING
clause, which describes important limitations and caveats for batch operations.
let request = Player.filter(...)...
// Fetch all deleted players
// DELETE FROM player RETURNING *
let deletedPlayers = try request.deleteAndFetchAll(db) // [Player]
// Fetch a selection of columns from the deleted rows
// DELETE FROM player RETURNING name
let statement = try request.deleteAndFetchStatement(db, selection: [Column("name")])
let deletedNames = try String.fetchSet(statement)
// Fetch all updated players
// UPDATE player SET score = score + 10 RETURNING *
let updatedPlayers = try request.updateAndFetchAll(db, [Column("score") += 10]) // [Player]
// Fetch a selection of columns from the updated rows
// UPDATE player SET score = score + 10 RETURNING score
let statement = try request.updateAndFetchStatement(
db, [Column("score") += 10],
select: [Column("score")])
let updatedScores = try Int.fetchAll(statement)
Your custom type may want to perform extra work when the persistence methods are invoked.
To this end, your record type can implement persistence callbacks. Callbacks are methods that get called at certain moments of a record's life cycle. With callbacks it is possible to write code that will run whenever an record is inserted, updated, or deleted.
In order to use a callback method, you need to provide its implementation. For example, a frequently used callback is didInsert
, in the case of auto-incremented database ids:
struct Player: MutablePersistableRecord {
var id: Int64?
// Update auto-incremented id upon successful insertion
mutating func didInsert(_ inserted: InsertionSuccess) {
id = inserted.rowID
}
}
try dbQueue.write { db in
var player = Player(id: nil, ...)
try player.insert(db)
print(player.id) // didInsert was called: prints some non-nil id
}
Callbacks can also help implementing record validation:
struct Link: PersistableRecord {
var url: URL
func willSave(_ db: Database) throws {
if url.host == nil {
throw ValidationError("url must be absolute.")
}
}
}
try link.insert(db) // Calls the willSave callback
try link.update(db) // Calls the willSave callback
try link.save(db) // Calls the willSave callback
try link.upsert(db) // Calls the willSave callback
Here is a list with all the available persistence callbacks, listed in the same order in which they will get called during the respective operations:
-
Inserting a record (all
record.insert
andrecord.upsert
methods)willSave
aroundSave
willInsert
aroundInsert
didInsert
didSave
-
Updating a record (all
record.update
methods)willSave
aroundSave
willUpdate
aroundUpdate
didUpdate
didSave
-
Deleting a record (only the
record.delete(_:)
method)willDelete
aroundDelete
didDelete
For detailed information about each callback, check the reference.
In the MutablePersistableRecord
protocol, willInsert
and didInsert
are mutating methods. In PersistableRecord
, they are not mutating.
Note: The
record.save(_:)
method performs an UPDATE if the record has a non-null primary key, and then, if no row was modified, an INSERT. It directly performs an INSERT if the record has no primary key, or a null primary key. It triggers update and/or insert callbacks accordingly.Warning: Callbacks are only invoked from persistence methods called on record instances. Callbacks are not invoked when you call a type method, perform a batch operations, or execute raw SQL.
Warning: When a
did***
callback is invoked, do not assume that the change is actually persisted on disk, because the database may still be inside an uncommitted transaction. When you need to handle transaction completions, use the afterNextTransaction(onCommit:onRollback:). For example:struct PictureFile: PersistableRecord { var path: String func willDelete(_ db: Database) { db.afterNextTransaction { _ in try? deleteFileOnDisk() } } }
When a record type maps a table with a single-column primary key, it is recommended to have it adopt the standard Identifiable protocol.
struct Player: Identifiable, FetchableRecord, PersistableRecord {
var id: Int64 // fulfills the Identifiable requirement
var name: String
var score: Int
}
When id
has a database-compatible type (Int64, Int, String, UUID, ...), the Identifiable
conformance unlocks type-safe record and request methods:
let player = try Player.find(db, id: 1) // Player
let player = try Player.fetchOne(db, id: 1) // Player?
let players = try Player.fetchAll(db, ids: [1, 2, 3]) // [Player]
let players = try Player.fetchSet(db, ids: [1, 2, 3]) // Set<Player>
let request = Player.filter(id: 1)
let request = Player.filter(ids: [1, 2, 3])
try Player.deleteOne(db, id: 1)
try Player.deleteAll(db, ids: [1, 2, 3])
Note: Not all record types can be made
Identifiable
, and not all tables have a single-column primary key. GRDB provides other methods that deal with primary and unique keys, but they won't check the type of their arguments:// Available on non-Identifiable types try Player.fetchOne(db, key: 1) try Player.fetchOne(db, key: ["email": "[email protected]"]) try Country.fetchAll(db, keys: ["FR", "US"]) try Citizenship.fetchOne(db, key: ["citizenId": 1, "countryCode": "FR"]) let request = Player.filter(key: 1) let request = Player.filter(keys: [1, 2, 3]) try Player.deleteOne(db, key: 1) try Player.deleteAll(db, keys: [1, 2, 3])
Note: It is not recommended to use
Identifiable
on record types that use an auto-incremented primary key:// AVOID declaring Identifiable conformance when key is auto-incremented struct Player { var id: Int64? // Not an id suitable for Identifiable var name: String var score: Int } extension Player: FetchableRecord, MutablePersistableRecord { // Update auto-incremented id upon successful insertion mutating func didInsert(_ inserted: InsertionSuccess) { id = inserted.rowID } }For a detailed rationale, please see issue #1435.
Some database tables have a single-column primary key which is not called "id":
try db.create(table: "country") { t in
t.primaryKey("isoCode", .text)
t.column("name", .text).notNull()
t.column("population", .integer).notNull()
}
In this case, Identifiable
conformance can be achieved, for example, by returning the primary key column from the id
property:
struct Country: Identifiable, FetchableRecord, PersistableRecord {
var isoCode: String
var name: String
var population: Int
// Fulfill the Identifiable requirement
var id: String { isoCode }
}
let france = try dbQueue.read { db in
try Country.fetchOne(db, id: "FR")
}
Record types that adopt an archival protocol (Codable, Encodable or Decodable) get free database support just by declaring conformance to the desired record protocols:
// Declare a record...
struct Player: Codable, FetchableRecord, PersistableRecord {
var name: String
var score: Int
}
// ...and there you go:
try dbQueue.write { db in
try Player(name: "Arthur", score: 100).insert(db)
let players = try Player.fetchAll(db)
}
Codable records encode and decode their properties according to their own implementation of the Encodable and Decodable protocols. Yet databases have specific requirements:
- Properties are always coded according to their preferred database representation, when they have one (all values that adopt the
DatabaseValueConvertible
protocol). - You can customize the encoding and decoding of dates and uuids.
- Complex properties (arrays, dictionaries, nested structs, etc.) are stored as JSON.
For more information about Codable records, see:
- JSON Columns
- Column Names Coding Strategies
- Data, Date, and UUID Coding Strategies
- The userInfo Dictionary
- Tip: Derive Columns from Coding Keys
💡 Tip: see the Demo Applications for sample code that uses Codable records.
When a Codable record contains a property that is not a simple value (Bool, Int, String, Date, Swift enums, etc.), that value is encoded and decoded as a JSON string. For example:
enum AchievementColor: String, Codable {
case bronze, silver, gold
}
struct Achievement: Codable {
var name: String
var color: AchievementColor
}
struct Player: Codable, FetchableRecord, PersistableRecord {
var name: String
var score: Int
var achievements: [Achievement] // stored in a JSON column
}
try dbQueue.write { db in
// INSERT INTO player (name, score, achievements)
// VALUES (
// 'Arthur',
// 100,
// '[{"color":"gold","name":"Use Codable Records"}]')
let achievement = Achievement(name: "Use Codable Records", color: .gold)
let player = Player(name: "Arthur", score: 100, achievements: [achievement])
try player.insert(db)
}
GRDB uses the standard JSONDecoder and JSONEncoder from Foundation. By default, Data values are handled with the .base64
strategy, Date with the .millisecondsSince1970
strategy, and non conforming floats with the .throw
strategy.
You can customize the JSON format by implementing those methods:
protocol FetchableRecord {
static func databaseJSONDecoder(for column: String) -> JSONDecoder
}
protocol EncodableRecord {
static func databaseJSONEncoder(for column: String) -> JSONEncoder
}
💡 Tip: Make sure you set the JSONEncoder
sortedKeys
option. This option makes sure that the JSON output is stable. This stability is required for Record Comparison to work as expected, and database observation tools such as ValueObservation to accurately recognize changed records.
By default, Codable Records store their values into database columns that match their coding keys: the teamID
property is stored into the teamID
column.
This behavior can be overridden, so that you can, for example, store the teamID
property into the team_id
column:
protocol FetchableRecord {
static var databaseColumnDecodingStrategy: DatabaseColumnDecodingStrategy { get }
}
protocol EncodableRecord {
static var databaseColumnEncodingStrategy: DatabaseColumnEncodingStrategy { get }
}
See DatabaseColumnDecodingStrategy and DatabaseColumnEncodingStrategy to learn about all available strategies.
By default, Codable Records encode and decode their Data properties as blobs, and Date and UUID properties as described in the general Date and DateComponents and UUID chapters.
To sum up: dates encode themselves in the "YYYY-MM-DD HH:MM:SS.SSS" format, in the UTC time zone, and decode a variety of date formats and timestamps. UUIDs encode themselves as 16-bytes data blobs, and decode both 16-bytes data blobs and strings such as "E621E1F8-C36C-495A-93FC-0C247A3E6E5F".
Those behaviors can be overridden:
protocol FetchableRecord {
static func databaseDataDecodingStrategy(for column: String) -> DatabaseDataDecodingStrategy
static func databaseDateDecodingStrategy(for column: String) -> DatabaseDateDecodingStrategy
}
protocol EncodableRecord {
static func databaseDataEncodingStrategy(for column: String) -> DatabaseDataEncodingStrategy
static func databaseDateEncodingStrategy(for column: String) -> DatabaseDateEncodingStrategy
static func databaseUUIDEncodingStrategy(for column: String) -> DatabaseUUIDEncodingStrategy
}
See DatabaseDataDecodingStrategy, DatabaseDateDecodingStrategy, DatabaseDataEncodingStrategy, DatabaseDateEncodingStrategy, and DatabaseUUIDEncodingStrategy to learn about all available strategies.
There is no customization of uuid decoding, because UUID can already decode all its encoded variants (16-bytes blobs and uuid strings, both uppercase and lowercase).
Customized coding strategies apply:
- When encoding and decoding database rows to and from records (fetching and persistence methods).
- In requests by single-column primary key:
fetchOne(_:id:)
,filter(id:)
,deleteAll(_:keys:)
, etc.
They do not apply in other requests based on data, date, or uuid values.
So make sure that those are properly encoded in your requests. For example:
struct Player: Codable, FetchableRecord, PersistableRecord, Identifiable {
// UUIDs are stored as strings
static func databaseUUIDEncodingStrategy(for column: String) -> DatabaseUUIDEncodingStrategy {
.uppercaseString
}
var id: UUID
...
}
try dbQueue.write { db in
let uuid = UUID()
let player = Player(id: uuid, ...)
// OK: inserts a player in the database, with a string uuid
try player.insert(db)
// OK: performs a string-based query, finds the inserted player
_ = try Player.filter(id: uuid).fetchOne(db)
// NOT OK: performs a blob-based query, fails to find the inserted player
_ = try Player.filter(Column("id") == uuid).fetchOne(db)
// OK: performs a string-based query, finds the inserted player
_ = try Player.filter(Column("id") == uuid.uuidString).fetchOne(db)
}
Your Codable Records can be stored in the database, but they may also have other purposes. In this case, you may need to customize their implementations of Decodable.init(from:)
and Encodable.encode(to:)
, depending on the context.
The standard way to provide such context is the userInfo
dictionary. Implement those properties:
protocol FetchableRecord {
static var databaseDecodingUserInfo: [CodingUserInfoKey: Any] { get }
}
protocol EncodableRecord {
static var databaseEncodingUserInfo: [CodingUserInfoKey: Any] { get }
}
For example, here is a Player type that customizes its decoding:
// A key that holds a decoder's name
let decoderName = CodingUserInfoKey(rawValue: "decoderName")!
struct Player: FetchableRecord, Decodable {
init(from decoder: Decoder) throws {
// Print the decoder name
let decoderName = decoder.userInfo[decoderName] as? String
print("Decoded from \(decoderName ?? "unknown decoder")")
...
}
}
You can have a specific decoding from JSON...
// prints "Decoded from JSON"
let decoder = JSONDecoder()
decoder.userInfo = [decoderName: "JSON"]
let player = try decoder.decode(Player.self, from: jsonData)
... and another one from database rows:
extension Player: FetchableRecord {
static var databaseDecodingUserInfo: [CodingUserInfoKey: Any] {
[decoderName: "database row"]
}
}
// prints "Decoded from database row"
let player = try Player.fetchOne(db, ...)
Note: make sure the
databaseDecodingUserInfo
anddatabaseEncodingUserInfo
properties are explicitly declared as[CodingUserInfoKey: Any]
. If they are not, the Swift compiler may silently miss the protocol requirement, resulting in sticky empty userInfo.
Codable types are granted with a CodingKeys enum. You can use them to safely define database columns:
struct Player: Codable {
var id: Int64
var name: String
var score: Int
}
extension Player: FetchableRecord, PersistableRecord {
enum Columns {
static let id = Column(CodingKeys.id)
static let name = Column(CodingKeys.name)
static let score = Column(CodingKeys.score)
}
}
See the query interface and Recommended Practices for Designing Record Types for further information.
Records that adopt the EncodableRecord protocol can compare against other records, or against previous versions of themselves.
This helps avoiding costly UPDATE statements when a record has not been edited.
- The
updateChanges
Methods - The
databaseEquals
Method - The
databaseChanges
andhasDatabaseChanges
Methods
The updateChanges
methods perform a database update of the changed columns only (and does nothing if record has no change).
-
updateChanges(_:from:)
This method lets you compare two records:
if let oldPlayer = try Player.fetchOne(db, id: 42) { var newPlayer = oldPlayer newPlayer.score = 100 if try newPlayer.updateChanges(db, from: oldPlayer) { print("player was modified, and updated in the database") } else { print("player was not modified, and database was not hit") } }
-
updateChanges(_:modify:)
This method lets you update a record in place:
if var player = try Player.fetchOne(db, id: 42) { let modified = try player.updateChanges(db) { $0.score = 100 } if modified { print("player was modified, and updated in the database") } else { print("player was not modified, and database was not hit") } }
This method returns whether two records have the same database representation:
let oldPlayer: Player = ...
var newPlayer: Player = ...
if newPlayer.databaseEquals(oldPlayer) == false {
try newPlayer.save(db)
}
Note: The comparison is performed on the database representation of records. As long as your record type adopts the EncodableRecord protocol, you don't need to care about Equatable.
databaseChanges(from:)
returns a dictionary of differences between two records:
let oldPlayer = Player(id: 1, name: "Arthur", score: 100)
let newPlayer = Player(id: 1, name: "Arthur", score: 1000)
for (column, oldValue) in try newPlayer.databaseChanges(from: oldPlayer) {
print("\(column) was \(oldValue)")
}
// prints "score was 100"
For an efficient algorithm which synchronizes the content of a database table with a JSON payload, check groue/SortedDifference.
GRDB records come with many default behaviors, that are designed to fit most situations. Many of those defaults can be customized for your specific needs:
- Persistence Callbacks: define what happens when you call a persistence method such as
player.insert(db)
- Conflict Resolution: Run
INSERT OR REPLACE
queries, and generally define what happens when a persistence method violates a unique index. - Columns Selected by a Request: define which columns are selected by requests such as
Player.fetchAll(db)
. - Beyond FetchableRecord: the FetchableRecord protocol is not the end of the story.
Codable Records have a few extra options:
- JSON Columns: control the format of JSON columns.
- Column Names Coding Strategies: control how coding keys are turned into column names
- [Date and UUID Coding Strategies]: control the format of Date and UUID properties in your Codable records.
- The userInfo Dictionary: adapt your Codable implementation for the database.
Insertions and updates can create conflicts: for example, a query may attempt to insert a duplicate row that violates a unique index.
Those conflicts normally end with an error. Yet SQLite let you alter the default behavior, and handle conflicts with specific policies. For example, the INSERT OR REPLACE
statement handles conflicts with the "replace" policy which replaces the conflicting row instead of throwing an error.
The five different policies are: abort (the default), replace, rollback, fail, and ignore.
SQLite let you specify conflict policies at two different places:
-
In the definition of the database table:
// CREATE TABLE player ( // id INTEGER PRIMARY KEY AUTOINCREMENT, // email TEXT UNIQUE ON CONFLICT REPLACE // ) try db.create(table: "player") { t in t.autoIncrementedPrimaryKey("id") t.column("email", .text).unique(onConflict: .replace) // <-- } // Despite the unique index on email, both inserts succeed. // The second insert replaces the first row: try db.execute(sql: "INSERT INTO player (email) VALUES (?)", arguments: ["[email protected]"]) try db.execute(sql: "INSERT INTO player (email) VALUES (?)", arguments: ["[email protected]"])
-
In each modification query:
// CREATE TABLE player ( // id INTEGER PRIMARY KEY AUTOINCREMENT, // email TEXT UNIQUE // ) try db.create(table: "player") { t in t.autoIncrementedPrimaryKey("id") t.column("email", .text).unique() } // Again, despite the unique index on email, both inserts succeed. try db.execute(sql: "INSERT OR REPLACE INTO player (email) VALUES (?)", arguments: ["[email protected]"]) try db.execute(sql: "INSERT OR REPLACE INTO player (email) VALUES (?)", arguments: ["[email protected]"])
When you want to handle conflicts at the query level, specify a custom persistenceConflictPolicy
in your type that adopts the PersistableRecord protocol. It will alter the INSERT and UPDATE queries run by the insert
, update
and save
persistence methods:
protocol MutablePersistableRecord {
/// The policy that handles SQLite conflicts when records are
/// inserted or updated.
///
/// This property is optional: its default value uses the ABORT
/// policy for both insertions and updates, so that GRDB generate
/// regular INSERT and UPDATE queries.
static var persistenceConflictPolicy: PersistenceConflictPolicy { get }
}
struct Player : MutablePersistableRecord {
static let persistenceConflictPolicy = PersistenceConflictPolicy(
insert: .replace,
update: .replace)
}
// INSERT OR REPLACE INTO player (...) VALUES (...)
try player.insert(db)
Note: If you specify the
ignore
policy for inserts, thedidInsert
callback will be called with some random id in case of failed insert. You can detect failed insertions withinsertAndFetch
:// How to detect failed `INSERT OR IGNORE`: // INSERT OR IGNORE INTO player ... RETURNING * do { let insertedPlayer = try player.insertAndFetch(db) { // Succesful insertion catch RecordError.recordNotFound { // Failed insertion due to IGNORE policy }Note: The
replace
policy may have to delete rows so that inserts and updates can succeed. Those deletions are not reported to transaction observers (this might change in a future release of SQLite).
Some GRDB users eventually discover that the FetchableRecord protocol does not fit all situations. Use cases that are not well handled by FetchableRecord include:
-
Your application needs polymorphic row decoding: it decodes some type or another, depending on the values contained in a database row.
-
Your application needs to decode rows with a context: each decoded value should be initialized with some extra value that does not come from the database.
Since those use cases are not well handled by FetchableRecord, don't try to implement them on top of this protocol: you'll just fight the framework.
We will show below how to declare a record type for the following database table:
try dbQueue.write { db in
try db.create(table: "place") { t in
t.autoIncrementedPrimaryKey("id")
t.column("title", .text).notNull()
t.column("isFavorite", .boolean).notNull().defaults(to: false)
t.column("longitude", .double).notNull()
t.column("latitude", .double).notNull()
}
}
Each one of the three examples below is correct. You will pick one or the other depending on your personal preferences and the requirements of your application:
Define a Codable struct, and adopt the record protocols you need
This is the shortest way to define a record type.
See the Record Protocols Overview, and Codable Records for more information.
struct Place: Codable {
var id: Int64?
var title: String
var isFavorite: Bool
private var latitude: CLLocationDegrees
private var longitude: CLLocationDegrees
var coordinate: CLLocationCoordinate2D {
get {
CLLocationCoordinate2D(
latitude: latitude,
longitude: longitude)
}
set {
latitude = newValue.latitude
longitude = newValue.longitude
}
}
}
// SQL generation
extension Place: TableRecord {
/// The table columns
enum Columns {
static let id = Column(CodingKeys.id)
static let title = Column(CodingKeys.title)
static let isFavorite = Column(CodingKeys.isFavorite)
static let latitude = Column(CodingKeys.latitude)
static let longitude = Column(CodingKeys.longitude)
}
}
// Fetching methods
extension Place: FetchableRecord { }
// Persistence methods
extension Place: MutablePersistableRecord {
// Update auto-incremented id upon successful insertion
mutating func didInsert(_ inserted: InsertionSuccess) {
id = inserted.rowID
}
}
Define a plain struct, and adopt the record protocols you need
See the Record Protocols Overview for more information.
struct Place {
var id: Int64?
var title: String
var isFavorite: Bool
var coordinate: CLLocationCoordinate2D
}
// SQL generation
extension Place: TableRecord {
/// The table columns
enum Columns: String, ColumnExpression {
case id, title, isFavorite, latitude, longitude
}
}
// Fetching methods
extension Place: FetchableRecord {
/// Creates a record from a database row
init(row: Row) {
id = row[Columns.id]
title = row[Columns.title]
isFavorite = row[Columns.isFavorite]
coordinate = CLLocationCoordinate2D(
latitude: row[Columns.latitude],
longitude: row[Columns.longitude])
}
}
// Persistence methods
extension Place: MutablePersistableRecord {
/// The values persisted in the database
func encode(to container: inout PersistenceContainer) {
container[Columns.id] = id
container[Columns.title] = title
container[Columns.isFavorite] = isFavorite
container[Columns.latitude] = coordinate.latitude
container[Columns.longitude] = coordinate.longitude
}
// Update auto-incremented id upon successful insertion
mutating func didInsert(_ inserted: InsertionSuccess) {
id = inserted.rowID
}
}
Define a plain struct optimized for fetching performance
This struct derives its persistence methods from the standard Encodable protocol (see Codable Records), but performs optimized row decoding by accessing database columns with numeric indexes.
See the Record Protocols Overview for more information.
struct Place: Encodable {
var id: Int64?
var title: String
var isFavorite: Bool
private var latitude: CLLocationDegrees
private var longitude: CLLocationDegrees
var coordinate: CLLocationCoordinate2D {
get {
CLLocationCoordinate2D(
latitude: latitude,
longitude: longitude)
}
set {
latitude = newValue.latitude
longitude = newValue.longitude
}
}
}
// SQL generation
extension Place: TableRecord {
/// The table columns
enum Columns {
static let id = Column(CodingKeys.id)
static let title = Column(CodingKeys.title)
static let isFavorite = Column(CodingKeys.isFavorite)
static let latitude = Column(CodingKeys.latitude)
static let longitude = Column(CodingKeys.longitude)
}
/// Arrange the selected columns and lock their order
static var databaseSelection: [any SQLSelectable] {
[
Columns.id,
Columns.title,
Columns.favorite,
Columns.latitude,
Columns.longitude,
]
}
}
// Fetching methods
extension Place: FetchableRecord {
/// Creates a record from a database row
init(row: Row) {
// For high performance, use numeric indexes that match the
// order of Place.databaseSelection
id = row[0]
title = row[1]
isFavorite = row[2]
coordinate = CLLocationCoordinate2D(
latitude: row[3],
longitude: row[4])
}
}
// Persistence methods
extension Place: MutablePersistableRecord {
// Update auto-incremented id upon successful insertion
mutating func didInsert(_ inserted: InsertionSuccess) {
id = inserted.rowID
}
}
The query interface lets you write pure Swift instead of SQL:
try dbQueue.write { db in
// Update database schema
try db.create(table: "wine") { t in ... }
// Fetch records
let wines = try Wine
.filter(originColumn == "Burgundy")
.order(priceColumn)
.fetchAll(db)
// Count
let count = try Wine
.filter(colorColumn == Color.red)
.fetchCount(db)
// Update
try Wine
.filter(originColumn == "Burgundy")
.updateAll(db, priceColumn *= 0.75)
// Delete
try Wine
.filter(corkedColumn == true)
.deleteAll(db)
}
You need to open a database connection before you can query the database.
Please bear in mind that the query interface can not generate all possible SQL queries. You may also prefer writing SQL, and this is just OK. From little snippets to full queries, your SQL skills are welcome:
try dbQueue.write { db in
// Update database schema (with SQL)
try db.execute(sql: "CREATE TABLE wine (...)")
// Fetch records (with SQL)
let wines = try Wine.fetchAll(db,
sql: "SELECT * FROM wine WHERE origin = ? ORDER BY price",
arguments: ["Burgundy"])
// Count (with an SQL snippet)
let count = try Wine
.filter(sql: "color = ?", arguments: [Color.red])
.fetchCount(db)
// Update (with SQL)
try db.execute(sql: "UPDATE wine SET price = price * 0.75 WHERE origin = 'Burgundy'")
// Delete (with SQL)
try db.execute(sql: "DELETE FROM wine WHERE corked")
}
So don't miss the SQL API.
Note: the generated SQL may change between GRDB releases, without notice: don't have your application rely on any specific SQL output.
- The Database Schema
- Requests
- Expressions
- Embedding SQL in Query Interface Requests
- Fetching from Requests
- Fetching by Key
- Testing for Record Existence
- Fetching Aggregated Values
- Delete Requests
- Update Requests
- Custom Requests
- 📘 Associations and Joins
- 📘 Common Table Expressions
- 📘 Query Interface Organization
📖 QueryInterfaceRequest
, Table
The query interface requests let you fetch values from the database:
let request = Player.filter(emailColumn != nil).order(nameColumn)
let players = try request.fetchAll(db) // [Player]
let count = try request.fetchCount(db) // Int
Query interface requests usually start from a type that adopts the TableRecord
protocol:
struct Player: TableRecord { ... }
// The request for all players:
let request = Player.all()
let players = try request.fetchAll(db) // [Player]
When you can not use a record type, use Table
:
// The request for all rows from the player table:
let table = Table("player")
let request = table.all()
let rows = try request.fetchAll(db) // [Row]
// The request for all players from the player table:
let table = Table<Player>("player")
let request = table.all()
let players = try request.fetchAll(db) // [Player]
Note: all examples in the documentation below use a record type, but you can always substitute a
Table
instead.
Next, declare the table columns that you want to use for filtering, or sorting:
let idColumn = Column("id")
let nameColumn = Column("name")
You can also declare column enums, if you prefer:
// Columns.id and Columns.name can be used just as
// idColumn and nameColumn declared above.
enum Columns: String, ColumnExpression {
case id
case name
}
You can now build requests with the following methods: all
, none
, select
, distinct
, filter
, matching
, group
, having
, order
, reversed
, limit
, joining
, including
, with
. All those methods return another request, which you can further refine by applying another method: Player.select(...).filter(...).order(...)
.
-
all()
,none()
: the requests for all rows, or no row.// SELECT * FROM player Player.all()
By default, all columns are selected. See Columns Selected by a Request.
-
select(...)
andselect(..., as:)
define the selected columns. See Columns Selected by a Request.// SELECT name FROM player Player.select(nameColumn, as: String.self)
-
annotated(with: expression...)
extends the selection.// SELECT *, (score + bonus) AS total FROM player Player.annotated(with: (scoreColumn + bonusColumn).forKey("total"))
-
annotated(with: aggregate)
extends the selection with association aggregates.// SELECT team.*, COUNT(DISTINCT player.id) AS playerCount // FROM team // LEFT JOIN player ON player.teamId = team.id // GROUP BY team.id Team.annotated(with: Team.players.count)
-
annotated(withRequired: association)
andannotated(withOptional: association)
extends the selection with Associations.// SELECT player.*, team.color // FROM player // JOIN team ON team.id = player.teamId Player.annotated(withRequired: Player.team.select(colorColumn))
-
distinct()
performs uniquing.// SELECT DISTINCT name FROM player Player.select(nameColumn, as: String.self).distinct()
-
filter(expression)
applies conditions.// SELECT * FROM player WHERE id IN (1, 2, 3) Player.filter([1,2,3].contains(idColumn)) // SELECT * FROM player WHERE (name IS NOT NULL) AND (height > 1.75) Player.filter(nameColumn != nil && heightColumn > 1.75)
-
filter(id:)
andfilter(ids:)
are type-safe methods available on Identifiable Records:// SELECT * FROM player WHERE id = 1 Player.filter(id: 1) // SELECT * FROM country WHERE isoCode IN ('FR', 'US') Country.filter(ids: ["FR", "US"])
-
filter(key:)
andfilter(keys:)
apply conditions on primary and unique keys:// SELECT * FROM player WHERE id = 1 Player.filter(key: 1) // SELECT * FROM country WHERE isoCode IN ('FR', 'US') Country.filter(keys: ["FR", "US"]) // SELECT * FROM citizenship WHERE citizenId = 1 AND countryCode = 'FR' Citizenship.filter(key: ["citizenId": 1, "countryCode": "FR"]) // SELECT * FROM player WHERE email = '[email protected]' Player.filter(key: ["email": "[email protected]"])
-
matching(pattern)
(FTS3, FTS5) performs full-text search.// SELECT * FROM document WHERE document MATCH 'sqlite database' let pattern = FTS3Pattern(matchingAllTokensIn: "SQLite database") Document.matching(pattern)
When the pattern is nil, no row will match.
-
group(expression, ...)
groups rows.// SELECT name, MAX(score) FROM player GROUP BY name Player .select(nameColumn, max(scoreColumn)) .group(nameColumn)
-
having(expression)
applies conditions on grouped rows.// SELECT team, MAX(score) FROM player GROUP BY team HAVING MIN(score) >= 1000 Player .select(teamColumn, max(scoreColumn)) .group(teamColumn) .having(min(scoreColumn) >= 1000)
-
having(aggregate)
applies conditions on grouped rows, according to an association aggregate.// SELECT team.* // FROM team // LEFT JOIN player ON player.teamId = team.id // GROUP BY team.id // HAVING COUNT(DISTINCT player.id) >= 5 Team.having(Team.players.count >= 5)
-
order(ordering, ...)
sorts.// SELECT * FROM player ORDER BY name Player.order(nameColumn) // SELECT * FROM player ORDER BY score DESC, name Player.order(scoreColumn.desc, nameColumn)
SQLite considers NULL values to be smaller than any other values for sorting purposes. Hence, NULLs naturally appear at the beginning of an ascending ordering and at the end of a descending ordering. With a custom SQLite build, this can be changed using
.ascNullsLast
and.descNullsFirst
:// SELECT * FROM player ORDER BY score ASC NULLS LAST Player.order(nameColumn.ascNullsLast)
Each
order
call clears any previous ordering:// SELECT * FROM player ORDER BY name Player.order(scoreColumn).order(nameColumn)
-
reversed()
reverses the eventual orderings.// SELECT * FROM player ORDER BY score ASC, name DESC Player.order(scoreColumn.desc, nameColumn).reversed()
If no ordering was already specified, this method has no effect:
// SELECT * FROM player Player.all().reversed()
-
limit(limit, offset: offset)
limits and pages results.// SELECT * FROM player LIMIT 5 Player.limit(5) // SELECT * FROM player LIMIT 5 OFFSET 10 Player.limit(5, offset: 10)
-
joining(required:)
,joining(optional:)
,including(required:)
,including(optional:)
, andincluding(all:)
fetch and join records through Associations.// SELECT player.*, team.* // FROM player // JOIN team ON team.id = player.teamId Player.including(required: Player.team)
-
with(cte)
embeds a common table expression:// WITH ... SELECT * FROM player let cte = CommonTableExpression(...) Player.with(cte)
-
Other requests that involve the primary key:
-
selectPrimaryKey(as:)
selects the primary key.// SELECT id FROM player Player.selectPrimaryKey(as: Int64.self) // QueryInterfaceRequest<Int64> // SELECT code FROM country Country.selectPrimaryKey(as: String.self) // QueryInterfaceRequest<String> // SELECT citizenId, countryCode FROM citizenship Citizenship.selectPrimaryKey(as: Row.self) // QueryInterfaceRequest<Row>
-
orderByPrimaryKey()
sorts by primary key.// SELECT * FROM player ORDER BY id Player.orderByPrimaryKey() // SELECT * FROM country ORDER BY code Country.orderByPrimaryKey() // SELECT * FROM citizenship ORDER BY citizenId, countryCode Citizenship.orderByPrimaryKey()
-
groupByPrimaryKey()
groups rows by primary key.
-
You can refine requests by chaining those methods:
// SELECT * FROM player WHERE (email IS NOT NULL) ORDER BY name
Player.order(nameColumn).filter(emailColumn != nil)
The select
, order
, group
, and limit
methods ignore and replace previously applied selection, orderings, grouping, and limits. On the opposite, filter
, matching
, and having
methods extend the query:
Player // SELECT * FROM player
.filter(nameColumn != nil) // WHERE (name IS NOT NULL)
.filter(emailColumn != nil) // AND (email IS NOT NULL)
.order(nameColumn) // - ignored -
.reversed() // - ignored -
.order(scoreColumn) // ORDER BY score
.limit(20, offset: 40) // - ignored -
.limit(10) // LIMIT 10
Raw SQL snippets are also accepted, with eventual arguments:
// SELECT DATE(creationDate), COUNT(*) FROM player WHERE name = 'Arthur' GROUP BY date(creationDate)
Player
.select(sql: "DATE(creationDate), COUNT(*)")
.filter(sql: "name = ?", arguments: ["Arthur"])
.group(sql: "DATE(creationDate)")
By default, query interface requests select all columns:
// SELECT * FROM player
struct Player: TableRecord { ... }
let request = Player.all()
// SELECT * FROM player
let table = Table("player")
let request = table.all()
The selection can be changed for each individual requests, or in the case of record-based requests, for all requests built from this record type.
The select(...)
and select(..., as:)
methods change the selection of a single request (see Fetching from Requests for detailed information):
let request = Player.select(max(Column("score")))
let maxScore = try Int.fetchOne(db, request) // Int?
let request = Player.select(max(Column("score")), as: Int.self)
let maxScore = try request.fetchOne(db) // Int?
The default selection for a record type is controlled by the databaseSelection
property:
struct RestrictedPlayer : TableRecord {
static let databaseTableName = "player"
static var databaseSelection: [any SQLSelectable] { [Column("id"), Column("name")] }
}
struct ExtendedPlayer : TableRecord {
static let databaseTableName = "player"
static var databaseSelection: [any SQLSelectable] { [AllColumns(), Column.rowID] }
}
// SELECT id, name FROM player
let request = RestrictedPlayer.all()
// SELECT *, rowid FROM player
let request = ExtendedPlayer.all()
Note: make sure the
databaseSelection
property is explicitly declared as[any SQLSelectable]
. If it is not, the Swift compiler may silently miss the protocol requirement, resulting in stickySELECT *
requests. To verify your setup, see the How do I print a request as SQL? FAQ.
Feed requests with SQL expressions built from your Swift code:
GRDB comes with a Swift version of many SQLite built-in operators, listed below. But not all: see Embedding SQL in Query Interface Requests for a way to add support for missing SQL operators.
-
=
,<>
,<
,<=
,>
,>=
,IS
,IS NOT
Comparison operators are based on the Swift operators
==
,!=
,===
,!==
,<
,<=
,>
,>=
:// SELECT * FROM player WHERE (name = 'Arthur') Player.filter(nameColumn == "Arthur") // SELECT * FROM player WHERE (name IS NULL) Player.filter(nameColumn == nil) // SELECT * FROM player WHERE (score IS 1000) Player.filter(scoreColumn === 1000) // SELECT * FROM rectangle WHERE width < height Rectangle.filter(widthColumn < heightColumn)
Subqueries are supported:
// SELECT * FROM player WHERE score = (SELECT max(score) FROM player) let maximumScore = Player.select(max(scoreColumn)) Player.filter(scoreColumn == maximumScore) // SELECT * FROM player WHERE score = (SELECT max(score) FROM player) let maximumScore = SQLRequest("SELECT max(score) FROM player") Player.filter(scoreColumn == maximumScore)
Note: SQLite string comparison, by default, is case-sensitive and not Unicode-aware. See string comparison if you need more control.
-
*
,/
,+
,-
SQLite arithmetic operators are derived from their Swift equivalent:
// SELECT ((temperature * 1.8) + 32) AS fahrenheit FROM planet Planet.select((temperatureColumn * 1.8 + 32).forKey("fahrenheit"))
Note: an expression like
nameColumn + "rrr"
will be interpreted by SQLite as a numerical addition (with funny results), not as a string concatenation. See theconcat
operator below.When you want to join a sequence of expressions with the
+
or*
operator, usejoined(operator:)
:// SELECT score + bonus + 1000 FROM player let values = [ scoreColumn, bonusColumn, 1000.databaseValue] Player.select(values.joined(operator: .add))
Note in the example above how you concatenate raw values:
1000.databaseValue
. A plain1000
would not compile.When the sequence is empty,
joined(operator: .add)
returns 0, andjoined(operator: .multiply)
returns 1. -
&
,|
,~
,<<
,>>
Bitwise operations (bitwise and, or, not, left shift, right shift) are derived from their Swift equivalent:
// SELECT mask & 2 AS isRocky FROM planet Planet.select((Column("mask") & 2).forKey("isRocky"))
-
||
Concatenate several strings:
// SELECT firstName || ' ' || lastName FROM player Player.select([firstNameColumn, " ".databaseValue, lastNameColumn].joined(operator: .concat))
Note in the example above how you concatenate raw strings:
" ".databaseValue
. A plain" "
would not compile.When the sequence is empty,
joined(operator: .concat)
returns the empty string. -
AND
,OR
,NOT
The SQL logical operators are derived from the Swift
&&
,||
and!
:// SELECT * FROM player WHERE ((NOT verified) OR (score < 1000)) Player.filter(!verifiedColumn || scoreColumn < 1000)
When you want to join a sequence of expressions with the
AND
orOR
operator, usejoined(operator:)
:// SELECT * FROM player WHERE (verified AND (score >= 1000) AND (name IS NOT NULL)) let conditions = [ verifiedColumn, scoreColumn >= 1000, nameColumn != nil] Player.filter(conditions.joined(operator: .and))
When the sequence is empty,
joined(operator: .and)
returns true, andjoined(operator: .or)
returns false:// SELECT * FROM player WHERE 1 Player.filter([].joined(operator: .and)) // SELECT * FROM player WHERE 0 Player.filter([].joined(operator: .or))
-
BETWEEN
,IN
,NOT IN
To check inclusion in a Swift sequence (array, set, range…), call the
contains
method:// SELECT * FROM player WHERE id IN (1, 2, 3) Player.filter([1, 2, 3].contains(idColumn)) // SELECT * FROM player WHERE id NOT IN (1, 2, 3) Player.filter(![1, 2, 3].contains(idColumn)) // SELECT * FROM player WHERE score BETWEEN 0 AND 1000 Player.filter((0...1000).contains(scoreColumn)) // SELECT * FROM player WHERE (score >= 0) AND (score < 1000) Player.filter((0..<1000).contains(scoreColumn)) // SELECT * FROM player WHERE initial BETWEEN 'A' AND 'N' Player.filter(("A"..."N").contains(initialColumn)) // SELECT * FROM player WHERE (initial >= 'A') AND (initial < 'N') Player.filter(("A"..<"N").contains(initialColumn))
To check inclusion inside a subquery, call the
contains
method as well:// SELECT * FROM player WHERE id IN (SELECT playerId FROM playerSelection) let selectedPlayerIds = PlayerSelection.select(playerIdColumn) Player.filter(selectedPlayerIds.contains(idColumn)) // SELECT * FROM player WHERE id IN (SELECT playerId FROM playerSelection) let selectedPlayerIds = SQLRequest("SELECT playerId FROM playerSelection") Player.filter(selectedPlayerIds.contains(idColumn))
To check inclusion inside a common table expression, call the
contains
method as well:// WITH selectedName AS (...) // SELECT * FROM player WHERE name IN selectedName let cte = CommonTableExpression(named: "selectedName", ...) Player .with(cte) .filter(cte.contains(nameColumn))
Note: SQLite string comparison, by default, is case-sensitive and not Unicode-aware. See string comparison if you need more control.
-
EXISTS
,NOT EXISTS
To check if a subquery would return rows, call the
exists
method:// Teams that have at least one other player // // SELECT * FROM team // WHERE EXISTS (SELECT * FROM player WHERE teamID = team.id) let teamAlias = TableAlias() let player = Player.filter(Column("teamID") == teamAlias[Column("id")]) let teams = Team.aliased(teamAlias).filter(player.exists()) // Teams that have no player // // SELECT * FROM team // WHERE NOT EXISTS (SELECT * FROM player WHERE teamID = team.id) let teams = Team.aliased(teamAlias).filter(!player.exists())
In the above example, you use a
TableAlias
in order to let a subquery refer to a column from another table.In the next example, which involves the same table twice, the table alias requires an explicit disambiguation with
TableAlias(name:)
:// Players who coach at least one other player // // SELECT coach.* FROM player coach // WHERE EXISTS (SELECT * FROM player WHERE coachId = coach.id) let coachAlias = TableAlias(name: "coach") let coachedPlayer = Player.filter(Column("coachId") == coachAlias[Column("id")]) let coaches = Player.aliased(coachAlias).filter(coachedPlayer.exists())
Finally, subqueries can also be expressed as SQL, with SQL Interpolation:
// SELECT coach.* FROM player coach // WHERE EXISTS (SELECT * FROM player WHERE coachId = coach.id) let coachedPlayer = SQLRequest("SELECT * FROM player WHERE coachId = \(coachAlias[Column("id")])") let coaches = Player.aliased(coachAlias).filter(coachedPlayer.exists())
-
LIKE
The SQLite LIKE operator is available as the
like
method:// SELECT * FROM player WHERE (email LIKE '%@example.com') Player.filter(emailColumn.like("%@example.com")) // SELECT * FROM book WHERE (title LIKE '%10\%%' ESCAPE '\') Player.filter(emailColumn.like("%10\\%%", escape: "\\"))
Note: the SQLite LIKE operator is case-insensitive but not Unicode-aware. For example, the expression
'a' LIKE 'A'
is true but'æ' LIKE 'Æ'
is false. -
MATCH
The full-text MATCH operator is available through FTS3Pattern (for FTS3 and FTS4 tables) and FTS5Pattern (for FTS5):
FTS3 and FTS4:
let pattern = FTS3Pattern(matchingAllTokensIn: "SQLite database") // SELECT * FROM document WHERE document MATCH 'sqlite database' Document.matching(pattern) // SELECT * FROM document WHERE content MATCH 'sqlite database' Document.filter(contentColumn.match(pattern))
FTS5:
let pattern = FTS5Pattern(matchingAllTokensIn: "SQLite database") // SELECT * FROM document WHERE document MATCH 'sqlite database' Document.matching(pattern)
-
AS
To give an alias to an expression, use the
forKey
method:// SELECT (score + bonus) AS total // FROM player Player.select((Column("score") + Column("bonus")).forKey("total"))
If you need to refer to this aliased column in another place of the request, use a detached column:
// SELECT (score + bonus) AS total // FROM player // ORDER BY total Player .select((Column("score") + Column("bonus")).forKey("total")) .order(Column("total").detached)
Unlike
Column("total")
, the detached columnColumn("total").detached
is never associated to the "player" table, so it is always rendered astotal
in the generated SQL, even when the request involves other tables via an association or a common table expression.
GRDB comes with a Swift version of many SQLite built-in functions, listed below. But not all: see Embedding SQL in Query Interface Requests for a way to add support for missing SQL functions.
-
ABS
,AVG
,COALESCE
,COUNT
,DATETIME
,JULIANDAY
,LENGTH
,MAX
,MIN
,SUM
,TOTAL
:Those are based on the
abs
,average
,coalesce
,count
,dateTime
,julianDay
,length
,max
,min
,sum
, andtotal
Swift functions:// SELECT MIN(score), MAX(score) FROM player Player.select(min(scoreColumn), max(scoreColumn)) // SELECT COUNT(name) FROM player Player.select(count(nameColumn)) // SELECT COUNT(DISTINCT name) FROM player Player.select(count(distinct: nameColumn)) // SELECT JULIANDAY(date, 'start of year') FROM game Game.select(julianDay(dateColumn, .startOfYear))
For more information about the functions
dateTime
andjulianDay
, see Date And Time Functions. -
CAST
Use the
cast
Swift function:// SELECT (CAST(wins AS REAL) / games) AS successRate FROM player Player.select((cast(winsColumn, as: .real) / gamesColumn).forKey("successRate"))
See CAST expressions for more information about SQLite conversions.
-
IFNULL
Use the Swift
??
operator:// SELECT IFNULL(name, 'Anonymous') FROM player Player.select(nameColumn ?? "Anonymous") // SELECT IFNULL(name, email) FROM player Player.select(nameColumn ?? emailColumn)
-
LOWER
,UPPER
The query interface does not give access to those SQLite functions. Nothing against them, but they are not unicode aware.
Instead, GRDB extends SQLite with SQL functions that call the Swift built-in string functions
capitalized
,lowercased
,uppercased
,localizedCapitalized
,localizedLowercased
andlocalizedUppercased
:Player.select(nameColumn.uppercased())
Note: When comparing strings, you'd rather use a collation:
let name: String = ... // Not recommended nameColumn.uppercased() == name.uppercased() // Better nameColumn.collating(.caseInsensitiveCompare) == name
-
Custom SQL functions and aggregates
You can apply your own custom SQL functions and aggregates:
let f = DatabaseFunction("f", ...) // SELECT f(name) FROM player Player.select(f.apply(nameColumn))
You will sometimes want to extend your query interface requests with SQL snippets. This can happen because GRDB does not provide a Swift interface for some SQL function or operator, or because you want to use an SQLite construct that GRDB does not support.
Support for extensibility is large, but not unlimited. All the SQL queries built by the query interface request have the shape below. If you need something else, you'll have to use raw SQL requests.
WITH ... -- 1
SELECT ... -- 2
FROM ... -- 3
JOIN ... -- 4
WHERE ... -- 5
GROUP BY ... -- 6
HAVING ... -- 7
ORDER BY ... -- 8
LIMIT ... -- 9
-
WITH ...
: see Common Table Expressions. -
SELECT ...
The selection can be provided as raw SQL:
// SELECT IFNULL(name, 'O''Brien'), score FROM player let request = Player.select(sql: "IFNULL(name, 'O''Brien'), score") // SELECT IFNULL(name, 'O''Brien'), score FROM player let defaultName = "O'Brien" let request = Player.select(sql: "IFNULL(name, ?), score", arguments: [suffix])
The selection can be provided with SQL Interpolation:
// SELECT IFNULL(name, 'O''Brien'), score FROM player let defaultName = "O'Brien" let request = Player.select(literal: "IFNULL(name, \(defaultName)), score")
The selection can be provided with a mix of Swift and SQL Interpolation:
// SELECT IFNULL(name, 'O''Brien') AS displayName, score FROM player let defaultName = "O'Brien" let displayName: SQL = "IFNULL(\(Column("name")), \(defaultName)) AS displayName" let request = Player.select(displayName, Column("score"))
When the custom SQL snippet should behave as a full-fledged expression, with support for the
+
Swift operator, theforKey
aliasing method, and all other SQL Operators, build an expression literal with theSQL.sqlExpression
method:// SELECT IFNULL(name, 'O''Brien') AS displayName, score FROM player let defaultName = "O'Brien" let displayName = SQL("IFNULL(\(Column("name")), \(defaultName))").sqlExpression let request = Player.select(displayName.forKey("displayName"), Column("score"))
Such expression literals allow you to build a reusable support library of SQL functions or operators that are missing from the query interface. For example, you can define a Swift
date
function:func date(_ value: some SQLSpecificExpressible) -> SQLExpression { SQL("DATE(\(value))").sqlExpression } // SELECT * FROM "player" WHERE DATE("createdAt") = '2020-01-23' let request = Player.filter(date(Column("createdAt")) == "2020-01-23")
See the Query Interface Organization for more information about
SQLSpecificExpressible
andSQLExpression
. -
FROM ...
: only one table is supported here. You can not customize this SQL part. -
JOIN ...
: joins are fully controlled by Associations. You can not customize this SQL part. -
WHERE ...
The WHERE clause can be provided as raw SQL:
// SELECT * FROM player WHERE score >= 1000 let request = Player.filter(sql: "score >= 1000") // SELECT * FROM player WHERE score >= 1000 let minScore = 1000 let request = Player.filter(sql: "score >= ?", arguments: [minScore])
The WHERE clause can be provided with SQL Interpolation:
// SELECT * FROM player WHERE score >= 1000 let minScore = 1000 let request = Player.filter(literal: "score >= \(minScore)")
The WHERE clause can be provided with a mix of Swift and SQL Interpolation:
// SELECT * FROM player WHERE (score >= 1000) AND (team = 'red') let minScore = 1000 let scoreCondition: SQL = "\(Column("score")) >= \(minScore)" let request = Player.filter(scoreCondition && Column("team") == "red")
See
SELECT ...
above for more SQL Interpolation examples. -
GROUP BY ...
The GROUP BY clause can be provided as raw SQL, SQL Interpolation, or a mix of Swift and SQL Interpolation, just as the selection and the WHERE clause (see above).
-
HAVING ...
The HAVING clause can be provided as raw SQL, SQL Interpolation, or a mix of Swift and SQL Interpolation, just as the selection and the WHERE clause (see above).
-
ORDER BY ...
The ORDER BY clause can be provided as raw SQL, SQL Interpolation, or a mix of Swift and SQL Interpolation, just as the selection and the WHERE clause (see above).
In order to support the
desc
andasc
query interface operators, and thereversed()
query interface method, you must provide your orderings as expression literals with theSQL.sqlExpression
method:// SELECT * FROM "player" // ORDER BY (score + bonus) ASC, name DESC let total = SQL("(score + bonus)").sqlExpression let request = Player .order(total.desc, Column("name")) .reversed()
-
LIMIT ...
: use thelimit(_:offset:)
method. You can not customize this SQL part.
Once you have a request, you can fetch the records at the origin of the request:
// Some request based on `Player`
let request = Player.filter(...)... // QueryInterfaceRequest<Player>
// Fetch players:
try request.fetchCursor(db) // A Cursor of Player
try request.fetchAll(db) // [Player]
try request.fetchSet(db) // Set<Player>
try request.fetchOne(db) // Player?
For example:
let allPlayers = try Player.fetchAll(db) // [Player]
let arthur = try Player.filter(nameColumn == "Arthur").fetchOne(db) // Player?
See fetching methods for information about the fetchCursor
, fetchAll
, fetchSet
and fetchOne
methods.
You sometimes want to fetch other values.
The simplest way is to use the request as an argument to a fetching method of the desired type:
// Fetch an Int
let request = Player.select(max(scoreColumn))
let maxScore = try Int.fetchOne(db, request) // Int?
// Fetch a Row
let request = Player.select(min(scoreColumn), max(scoreColumn))
let row = try Row.fetchOne(db, request)! // Row
let minScore = row[0] as Int?
let maxScore = row[1] as Int?
You can also change the request so that it knows the type it has to fetch:
-
With
asRequest(of:)
, useful when you use Associations:struct BookInfo: FetchableRecord, Decodable { var book: Book var author: Author } // A request of BookInfo let request = Book .including(required: Book.author) .asRequest(of: BookInfo.self) let bookInfos = try dbQueue.read { db in try request.fetchAll(db) // [BookInfo] }
-
With
select(..., as:)
, which is handy when you change the selection:// A request of Int let request = Player.select(max(scoreColumn), as: Int.self) let maxScore = try dbQueue.read { db in try request.fetchOne(db) // Int? }
Fetching records according to their primary key is a common task.
Identifiable Records can use the type-safe methods find(_:id:)
, fetchOne(_:id:)
, fetchAll(_:ids:)
and fetchSet(_:ids:)
:
try Player.find(db, id: 1) // Player
try Player.fetchOne(db, id: 1) // Player?
try Country.fetchAll(db, ids: ["FR", "US"]) // [Countries]
All record types can use find(_:key:)
, fetchOne(_:key:)
, fetchAll(_:keys:)
and fetchSet(_:keys:)
that apply conditions on primary and unique keys:
try Player.find(db, key: 1) // Player
try Player.fetchOne(db, key: 1) // Player?
try Country.fetchAll(db, keys: ["FR", "US"]) // [Country]
try Player.fetchOne(db, key: ["email": "[email protected]"]) // Player?
try Citizenship.fetchOne(db, key: ["citizenId": 1, "countryCode": "FR"]) // Citizenship?
When the table has no explicit primary key, GRDB uses the hidden rowid
column:
// SELECT * FROM document WHERE rowid = 1
try Document.fetchOne(db, key: 1) // Document?
When you want to build a request and plan to fetch from it later, use a filter
method:
let request = Player.filter(id: 1)
let request = Country.filter(ids: ["FR", "US"])
let request = Player.filter(key: ["email": "[email protected]"])
let request = Citizenship.filter(key: ["citizenId": 1, "countryCode": "FR"])
You can check if a request has matching rows in the database.
// Some request based on `Player`
let request = Player.filter(...)...
// Check for player existence:
let noSuchPlayer = try request.isEmpty(db) // Bool
You should check for emptiness instead of counting:
// Correct
let noSuchPlayer = try request.fetchCount(db) == 0
// Even better
let noSuchPlayer = try request.isEmpty(db)
You can also check if a given primary or unique key exists in the database.
Identifiable Records can use the type-safe method exists(_:id:)
:
try Player.exists(db, id: 1)
try Country.exists(db, id: "FR")
All record types can use exists(_:key:)
that can check primary and unique keys:
try Player.exists(db, key: 1)
try Country.exists(db, key: "FR")
try Player.exists(db, key: ["email": "[email protected]"])
try Citizenship.exists(db, key: ["citizenId": 1, "countryCode": "FR"])
You should check for key existence instead of fetching a record and checking for nil:
// Correct
let playerExists = try Player.fetchOne(db, id: 1) != nil
// Even better
let playerExists = try Player.exists(db, id: 1)
Requests can count. The fetchCount()
method returns the number of rows that would be returned by a fetch request:
// SELECT COUNT(*) FROM player
let count = try Player.fetchCount(db) // Int
// SELECT COUNT(*) FROM player WHERE email IS NOT NULL
let count = try Player.filter(emailColumn != nil).fetchCount(db)
// SELECT COUNT(DISTINCT name) FROM player
let count = try Player.select(nameColumn).distinct().fetchCount(db)
// SELECT COUNT(*) FROM (SELECT DISTINCT name, score FROM player)
let count = try Player.select(nameColumn, scoreColumn).distinct().fetchCount(db)
Other aggregated values can also be selected and fetched (see SQL Functions):
let request = Player.select(max(scoreColumn))
let maxScore = try Int.fetchOne(db, request) // Int?
let request = Player.select(min(scoreColumn), max(scoreColumn))
let row = try Row.fetchOne(db, request)! // Row
let minScore = row[0] as Int?
let maxScore = row[1] as Int?
Requests can delete records, with the deleteAll()
method:
// DELETE FROM player
try Player.deleteAll(db)
// DELETE FROM player WHERE team = 'red'
try Player
.filter(teamColumn == "red")
.deleteAll(db)
// DELETE FROM player ORDER BY score LIMIT 10
try Player
.order(scoreColumn)
.limit(10)
.deleteAll(db)
Note Deletion methods are available on types that adopt the TableRecord protocol, and
Table
:struct Player: TableRecord { ... } try Player.deleteAll(db) // Fine try Table("player").deleteAll(db) // Just as fine
Deleting records according to their primary key is a common task.
Identifiable Records can use the type-safe methods deleteOne(_:id:)
and deleteAll(_:ids:)
:
try Player.deleteOne(db, id: 1)
try Country.deleteAll(db, ids: ["FR", "US"])
All record types can use deleteOne(_:key:)
and deleteAll(_:keys:)
that apply conditions on primary and unique keys:
try Player.deleteOne(db, key: 1)
try Country.deleteAll(db, keys: ["FR", "US"])
try Player.deleteOne(db, key: ["email": "[email protected]"])
try Citizenship.deleteOne(db, key: ["citizenId": 1, "countryCode": "FR"])
When the table has no explicit primary key, GRDB uses the hidden rowid
column:
// DELETE FROM document WHERE rowid = 1
try Document.deleteOne(db, id: 1) // Document?
Requests can batch update records. The updateAll()
method accepts column assignments defined with the set(to:)
method:
// UPDATE player SET score = 0, isHealthy = 1, bonus = NULL
try Player.updateAll(db,
Column("score").set(to: 0),
Column("isHealthy").set(to: true),
Column("bonus").set(to: nil))
// UPDATE player SET score = 0 WHERE team = 'red'
try Player
.filter(Column("team") == "red")
.updateAll(db, Column("score").set(to: 0))
// UPDATE player SET top = 1 ORDER BY score DESC LIMIT 10
try Player
.order(Column("score").desc)
.limit(10)
.updateAll(db, Column("top").set(to: true))
// UPDATE country SET population = 67848156 WHERE id = 'FR'
try Country
.filter(id: "FR")
.updateAll(db, Column("population").set(to: 67_848_156))
Column assignments accept any expression:
// UPDATE player SET score = score + (bonus * 2)
try Player.updateAll(db, Column("score").set(to: Column("score") + Column("bonus") * 2))
As a convenience, you can also use the +=
, -=
, *=
, or /=
operators:
// UPDATE player SET score = score + (bonus * 2)
try Player.updateAll(db, Column("score") += Column("bonus") * 2)
Default Conflict Resolution rules apply, and you may also provide a specific one:
// UPDATE OR IGNORE player SET ...
try Player.updateAll(db, onConflict: .ignore, /* assignments... */)
Note The
updateAll
method is available on types that adopt the TableRecord protocol, andTable
:struct Player: TableRecord { ... } try Player.updateAll(db, ...) // Fine try Table("player").updateAll(db, ...) // Just as fine
Until now, we have seen requests created from any type that adopts the TableRecord protocol:
let request = Player.all() // QueryInterfaceRequest<Player>
Those requests of type QueryInterfaceRequest
can fetch and count:
try request.fetchCursor(db) // A Cursor of Player
try request.fetchAll(db) // [Player]
try request.fetchSet(db) // Set<Player>
try request.fetchOne(db) // Player?
try request.fetchCount(db) // Int
When the query interface can not generate the SQL you need, you can still fallback to raw SQL:
// Custom SQL is always welcome
try Player.fetchAll(db, sql: "SELECT ...") // [Player]
But you may prefer to bring some elegance back in, and build custom requests:
// No custom SQL in sight
try Player.customRequest().fetchAll(db) // [Player]
To build custom requests, you can use one of the built-in requests or derive requests from other requests.
-
SQLRequest is a fetch request built from raw SQL. For example:
extension Player { static func filter(color: Color) -> SQLRequest<Player> { SQLRequest<Player>( sql: "SELECT * FROM player WHERE color = ?" arguments: [color]) } } // [Player] try Player.filter(color: .red).fetchAll(db)
SQLRequest supports SQL Interpolation:
extension Player { static func filter(color: Color) -> SQLRequest<Player> { "SELECT * FROM player WHERE color = \(color)" } }
-
The
asRequest(of:)
method changes the type fetched by the request. It is useful, for example, when you use Associations:struct BookInfo: FetchableRecord, Decodable { var book: Book var author: Author } let request = Book .including(required: Book.author) .asRequest(of: BookInfo.self) // [BookInfo] try request.fetchAll(db)
-
The
adapted(_:)
method eases the consumption of complex rows with row adapters. SeeRowAdapter
andsplittingRowAdapters(columnCounts:)
for a sample code that usesadapted(_:)
.
GRDB can encrypt your database with SQLCipher v3.4+.
Use CocoaPods, and specify in your Podfile
:
# GRDB with SQLCipher 4
pod 'GRDB.swift/SQLCipher'
pod 'SQLCipher', '~> 4.0'
# GRDB with SQLCipher 3
pod 'GRDB.swift/SQLCipher'
pod 'SQLCipher', '~> 3.4'
Make sure you remove any existing pod 'GRDB.swift'
from your Podfile. GRDB.swift/SQLCipher
must be the only active GRDB pod in your whole project, or you will face linker or runtime errors, due to the conflicts between SQLCipher and the system SQLite.
- Creating or Opening an Encrypted Database
- Changing the Passphrase of an Encrypted Database
- Exporting a Database to an Encrypted Database
- Security Considerations
You create and open an encrypted database by providing a passphrase to your database connection:
var config = Configuration()
config.prepareDatabase { db in
try db.usePassphrase("secret")
}
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config)
It is also in prepareDatabase
that you perform other SQLCipher configuration steps that must happen early in the lifetime of a SQLCipher connection. For example:
var config = Configuration()
config.prepareDatabase { db in
try db.usePassphrase("secret")
try db.execute(sql: "PRAGMA cipher_page_size = ...")
try db.execute(sql: "PRAGMA kdf_iter = ...")
}
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config)
When you want to open an existing SQLCipher 3 database with SQLCipher 4, you may want to run the cipher_compatibility
pragma:
// Open an SQLCipher 3 database with SQLCipher 4
var config = Configuration()
config.prepareDatabase { db in
try db.usePassphrase("secret")
try db.execute(sql: "PRAGMA cipher_compatibility = 3")
}
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config)
See SQLCipher 4.0.0 Release and Upgrading to SQLCipher 4 for more information.
You can change the passphrase of an already encrypted database.
When you use a database queue, open the database with the old passphrase, and then apply the new passphrase:
try dbQueue.write { db in
try db.changePassphrase("newSecret")
}
When you use a database pool, make sure that no concurrent read can happen by changing the passphrase within the barrierWriteWithoutTransaction
block. You must also ensure all future reads open a new database connection by calling the invalidateReadOnlyConnections
method:
try dbPool.barrierWriteWithoutTransaction { db in
try db.changePassphrase("newSecret")
dbPool.invalidateReadOnlyConnections()
}
Note: When an application wants to keep on using a database queue or pool after the passphrase has changed, it is responsible for providing the correct passphrase to the
usePassphrase
method called in the database preparation function. Consider:// WRONG: this won't work across a passphrase change let passphrase = try getPassphrase() var config = Configuration() config.prepareDatabase { db in try db.usePassphrase(passphrase) } // CORRECT: get the latest passphrase when it is needed var config = Configuration() config.prepareDatabase { db in let passphrase = try getPassphrase() try db.usePassphrase(passphrase) }
Note: The
DatabasePool.barrierWriteWithoutTransaction
method does not prevent database snapshots from accessing the database during the passphrase change, or after the new passphrase has been applied to the database. Those database accesses may throw errors. Applications should provide their own mechanism for invalidating open snapshots before the passphrase is changed.
Note: Instead of changing the passphrase "in place" as described here, you can also export the database in a new encrypted database that uses the new passphrase. See Exporting a Database to an Encrypted Database.
Providing a passphrase won't encrypt a clear-text database that already exists, though. SQLCipher can't do that, and you will get an error instead: SQLite error 26: file is encrypted or is not a database
.
Instead, create a new encrypted database, at a distinct location, and export the content of the existing database. This can both encrypt a clear-text database, or change the passphrase of an encrypted database.
The technique to do that is documented by SQLCipher.
With GRDB, it gives:
// The existing database
let existingDBQueue = try DatabaseQueue(path: "/path/to/existing.db")
// The new encrypted database, at some distinct location:
var config = Configuration()
config.prepareDatabase { db in
try db.usePassphrase("secret")
}
let newDBQueue = try DatabaseQueue(path: "/path/to/new.db", configuration: config)
try existingDBQueue.inDatabase { db in
try db.execute(
sql: """
ATTACH DATABASE ? AS encrypted KEY ?;
SELECT sqlcipher_export('encrypted');
DETACH DATABASE encrypted;
""",
arguments: [newDBQueue.path, "secret"])
}
// Now the export is completed, and the existing database can be deleted.
It is recommended to avoid keeping the passphrase in memory longer than necessary. To do this, make sure you load the passphrase from the prepareDatabase
method:
// NOT RECOMMENDED: this keeps the passphrase in memory longer than necessary
let passphrase = try getPassphrase()
var config = Configuration()
config.prepareDatabase { db in
try db.usePassphrase(passphrase)
}
// RECOMMENDED: only load the passphrase when it is needed
var config = Configuration()
config.prepareDatabase { db in
let passphrase = try getPassphrase()
try db.usePassphrase(passphrase)
}
This technique helps manages the lifetime of the passphrase, although keep in mind that the content of a String may remain intact in memory long after the object has been released.
For even better control over the lifetime of the passphrase in memory, use a Data object which natively provides the resetBytes
function.
// RECOMMENDED: only load the passphrase when it is needed and reset its content immediately after use
var config = Configuration()
config.prepareDatabase { db in
var passphraseData = try getPassphraseData() // Data
defer {
passphraseData.resetBytes(in: 0..<passphraseData.count)
}
try db.usePassphrase(passphraseData)
}
Some demanding users will want to go further, and manage the lifetime of the raw passphrase bytes. See below.
GRDB offers convenience methods for providing the database passphrases as Swift strings: usePassphrase(_:)
and changePassphrase(_:)
. Those methods don't keep the passphrase String in memory longer than necessary. But they are as secure as the standard String type: the lifetime of actual passphrase bytes in memory is not under control.
When you want to precisely manage the passphrase bytes, talk directly to SQLCipher, using its raw C functions.
For example:
var config = Configuration()
config.prepareDatabase { db in
... // Carefully load passphrase bytes
let code = sqlite3_key(db.sqliteConnection, /* passphrase bytes */)
... // Carefully dispose passphrase bytes
guard code == SQLITE_OK else {
throw DatabaseError(
resultCode: ResultCode(rawValue: code),
message: db.lastErrorMessage)
}
}
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config)
When the passphrase is securely stored in the system keychain, your application can protect it using the kSecAttrAccessible
attribute.
Such protection prevents GRDB from creating SQLite connections when the passphrase is not available:
var config = Configuration()
config.prepareDatabase { db in
let passphrase = try loadPassphraseFromSystemKeychain()
try db.usePassphrase(passphrase)
}
// Success if and only if the passphrase is available
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config)
For the same reason, database pools, which open SQLite connections on demand, may fail at any time as soon as the passphrase becomes unavailable:
// Success if and only if the passphrase is available
let dbPool = try DatabasePool(path: dbPath, configuration: config)
// May fail if passphrase has turned unavailable
try dbPool.read { ... }
// May trigger value observation failure if passphrase has turned unavailable
try dbPool.write { ... }
Because DatabasePool maintains a pool of long-lived SQLite connections, some database accesses will use an existing connection, and succeed. And some other database accesses will fail, as soon as the pool wants to open a new connection. It is impossible to predict which accesses will succeed or fail.
For the same reason, a database queue, which also maintains a long-lived SQLite connection, will remain available even after the passphrase has turned unavailable.
Applications are thus responsible for protecting database accesses when the passphrase is unavailable. To this end, they can use Data Protection. They can also destroy their instances of database queue or pool when the passphrase becomes unavailable.
You can backup (copy) a database into another.
Backups can for example help you copying an in-memory database to and from a database file when you implement NSDocument subclasses.
let source: DatabaseQueue = ... // or DatabasePool
let destination: DatabaseQueue = ... // or DatabasePool
try source.backup(to: destination)
The backup
method blocks the current thread until the destination database contains the same contents as the source database.
When the source is a database pool, concurrent writes can happen during the backup. Those writes may, or may not, be reflected in the backup, but they won't trigger any error.
Database
has an analogous backup
method.
let source: DatabaseQueue = ... // or DatabasePool
let destination: DatabaseQueue = ... // or DatabasePool
try source.write { sourceDb in
try destination.barrierWriteWithoutTransaction { destDb in
try sourceDb.backup(to: destDb)
}
}
This method allows for the choice of source and destination Database
handles with which to backup the database.
The backup
methods take optional pagesPerStep
and progress
parameters. Together these parameters can be used to track a database backup in progress and abort an incomplete backup.
When pagesPerStep
is provided, the database backup is performed in steps. At each step, no more than pagesPerStep
database pages are copied from the source to the destination. The backup proceeds one step at a time until all pages have been copied.
When a progress
callback is provided, progress
is called after every backup step, including the last. Even if a non-default pagesPerStep
is specified or the backup is otherwise completed in a single step, the progress
callback will be called.
try source.backup(
to: destination,
pagesPerStep: ...)
{ backupProgress in
print("Database backup progress:", backupProgress)
}
If a call to progress
throws when backupProgress.isComplete == false
, the backup will be aborted and the error rethrown. However, if a call to progress
throws when backupProgress.isComplete == true
, the backup is unaffected and the error is silently ignored.
Warning: Passing non-default values of
pagesPerStep
orprogress
to the backup methods is an advanced API intended to provide additional capabilities to expert users. GRDB's backup API provides a faithful, low-level wrapper to the underlying SQLite online backup API. GRDB's documentation is not a comprehensive substitute for the official SQLite documentation of their backup API.
The interrupt()
method causes any pending database operation to abort and return at its earliest opportunity.
It can be called from any thread.
dbQueue.interrupt()
dbPool.interrupt()
A call to interrupt()
that occurs when there are no running SQL statements is a no-op and has no effect on SQL statements that are started after interrupt()
returns.
A database operation that is interrupted will throw a DatabaseError with code SQLITE_INTERRUPT
. If the interrupted SQL operation is an INSERT, UPDATE, or DELETE that is inside an explicit transaction, then the entire transaction will be rolled back automatically. If the rolled back transaction was started by a transaction-wrapping method such as DatabaseWriter.write
or Database.inTransaction
, then all database accesses will throw a DatabaseError with code SQLITE_ABORT
until the wrapping method returns.
For example:
try dbQueue.write { db in
try Player(...).insert(db) // throws SQLITE_INTERRUPT
try Player(...).insert(db) // not executed
} // throws SQLITE_INTERRUPT
try dbQueue.write { db in
do {
try Player(...).insert(db) // throws SQLITE_INTERRUPT
} catch { }
} // throws SQLITE_ABORT
try dbQueue.write { db in
do {
try Player(...).insert(db) // throws SQLITE_INTERRUPT
} catch { }
try Player(...).insert(db) // throws SQLITE_ABORT
} // throws SQLITE_ABORT
You can catch both SQLITE_INTERRUPT
and SQLITE_ABORT
errors:
do {
try dbPool.write { db in ... }
} catch DatabaseError.SQLITE_INTERRUPT, DatabaseError.SQLITE_ABORT {
// Oops, the database was interrupted.
}
For more information, see Interrupt A Long-Running Query.
SQL injection is a technique that lets an attacker nuke your database.
Here is an example of code that is vulnerable to SQL injection:
// BAD BAD BAD
let id = 1
let name = textField.text
try dbQueue.write { db in
try db.execute(sql: "UPDATE students SET name = '\(name)' WHERE id = \(id)")
}
If the user enters a funny string like Robert'; DROP TABLE students; --
, SQLite will see the following SQL, and drop your database table instead of updating a name as intended:
UPDATE students SET name = 'Robert';
DROP TABLE students;
--' WHERE id = 1
To avoid those problems, never embed raw values in your SQL queries. The only correct technique is to provide arguments to your raw SQL queries:
let name = textField.text
try dbQueue.write { db in
// Good
try db.execute(
sql: "UPDATE students SET name = ? WHERE id = ?",
arguments: [name, id])
// Just as good
try db.execute(
sql: "UPDATE students SET name = :name WHERE id = :id",
arguments: ["name": name, "id": id])
}
When you use records and the query interface, GRDB always prevents SQL injection for you:
let id = 1
let name = textField.text
try dbQueue.write { db in
if var student = try Student.fetchOne(db, id: id) {
student.name = name
try student.update(db)
}
}
GRDB can throw DatabaseError, RecordError, or crash your program with a fatal error.
Considering that a local database is not some JSON loaded from a remote server, GRDB focuses on trusted databases. Dealing with untrusted databases requires extra care.
DatabaseError are thrown on SQLite errors:
do {
try Pet(masterId: 1, name: "Bobby").insert(db)
} catch let error as DatabaseError {
// The SQLite error code: 19 (SQLITE_CONSTRAINT)
error.resultCode
// The extended error code: 787 (SQLITE_CONSTRAINT_FOREIGNKEY)
error.extendedResultCode
// The eventual SQLite message: FOREIGN KEY constraint failed
error.message
// The eventual erroneous SQL query
// "INSERT INTO pet (masterId, name) VALUES (?, ?)"
error.sql
// The eventual SQL arguments
// [1, "Bobby"]
error.arguments
// Full error description
// > SQLite error 19: FOREIGN KEY constraint failed -
// > while executing `INSERT INTO pet (masterId, name) VALUES (?, ?)`
error.description
}
If you want to see statement arguments in the error description, make statement arguments public.
SQLite uses results codes to distinguish between various errors.
You can catch a DatabaseError and match on result codes:
do {
try ...
} catch let error as DatabaseError {
switch error {
case DatabaseError.SQLITE_CONSTRAINT_FOREIGNKEY:
// foreign key constraint error
case DatabaseError.SQLITE_CONSTRAINT:
// any other constraint error
default:
// any other database error
}
}
You can also directly match errors on result codes:
do {
try ...
} catch DatabaseError.SQLITE_CONSTRAINT_FOREIGNKEY {
// foreign key constraint error
} catch DatabaseError.SQLITE_CONSTRAINT {
// any other constraint error
} catch {
// any other database error
}
Each DatabaseError has two codes: an extendedResultCode
(see extended result code), and a less precise resultCode
(see primary result code). Extended result codes are refinements of primary result codes, as SQLITE_CONSTRAINT_FOREIGNKEY
is to SQLITE_CONSTRAINT
, for example.
Warning: SQLite has progressively introduced extended result codes across its versions. The SQLite release notes are unfortunately not quite clear about that: write your handling of extended result codes with care.
RecordError is thrown by the PersistableRecord protocol when the update
method could not find any row to update:
do {
try player.update(db)
} catch let RecordError.recordNotFound(databaseTableName: table, key: key) {
print("Key \(key) was not found in table \(table).")
}
RecordError is also thrown by the FetchableRecord protocol when the find
method does not find any record:
do {
let player = try Player.find(db, id: 42)
} catch let RecordError.recordNotFound(databaseTableName: table, key: key) {
print("Key \(key) was not found in table \(table).")
}
Fatal errors notify that the program, or the database, has to be changed.
They uncover programmer errors, false assumptions, and prevent misuses. Here are a few examples:
-
The code asks for a non-optional value, when the database contains NULL:
// fatal error: could not convert NULL to String. let name: String = row["name"]
Solution: fix the contents of the database, use NOT NULL constraints, or load an optional:
let name: String? = row["name"]
-
Conversion from database value to Swift type fails:
// fatal error: could not convert "Mom’s birthday" to Date. let date: Date = row["date"] // fatal error: could not convert "" to URL. let url: URL = row["url"]
Solution: fix the contents of the database, or use DatabaseValue to handle all possible cases:
let dbValue: DatabaseValue = row["date"] if dbValue.isNull { // Handle NULL } else if let date = Date.fromDatabaseValue(dbValue) { // Handle valid date } else { // Handle invalid date }
-
The database can't guarantee that the code does what it says:
// fatal error: table player has no unique index on column email try Player.deleteOne(db, key: ["email": "[email protected]"])
Solution: add a unique index to the player.email column, or use the
deleteAll
method to make it clear that you may delete more than one row:try Player.filter(Column("email") == "[email protected]").deleteAll(db)
-
Database connections are not reentrant:
// fatal error: Database methods are not reentrant. dbQueue.write { db in dbQueue.write { db in ... } }
Solution: avoid reentrancy, and instead pass a database connection along.
Let's consider the code below:
let sql = "SELECT ..."
// Some untrusted arguments for the query
let arguments: [String: Any] = ...
let rows = try Row.fetchCursor(db, sql: sql, arguments: StatementArguments(arguments))
while let row = try rows.next() {
// Some untrusted database value:
let date: Date? = row[0]
}
It has two opportunities to throw fatal errors:
- Untrusted arguments: The dictionary may contain values that do not conform to the DatabaseValueConvertible protocol, or may miss keys required by the statement.
- Untrusted database content: The row may contain a non-null value that can't be turned into a date.
In such a situation, you can still avoid fatal errors by exposing and handling each failure point, one level down in the GRDB API:
// Untrusted arguments
if let arguments = StatementArguments(arguments) {
let statement = try db.makeStatement(sql: sql)
try statement.setArguments(arguments)
var cursor = try Row.fetchCursor(statement)
while let row = try iterator.next() {
// Untrusted database content
let dbValue: DatabaseValue = row[0]
if dbValue.isNull {
// Handle NULL
if let date = Date.fromDatabaseValue(dbValue) {
// Handle valid date
} else {
// Handle invalid date
}
}
}
See Statement
and DatabaseValue for more information.
SQLite can be configured to invoke a callback function containing an error code and a terse error message whenever anomalies occur.
This global error callback must be configured early in the lifetime of your application:
Database.logError = { (resultCode, message) in
NSLog("%@", "SQLite error \(resultCode): \(message)")
}
Warning: Database.logError must be set before any database connection is opened. This includes the connections that your application opens with GRDB, but also connections opened by other tools, such as third-party libraries. Setting it after a connection has been opened is an SQLite misuse, and has no effect.
See The Error And Warning Log for more information.
SQLite lets you store unicode strings in the database.
However, SQLite does not provide any unicode-aware string transformations or comparisons.
The UPPER
and LOWER
built-in SQLite functions are not unicode-aware:
// "JéRôME"
try String.fetchOne(db, sql: "SELECT UPPER('Jérôme')")
GRDB extends SQLite with SQL functions that call the Swift built-in string functions capitalized
, lowercased
, uppercased
, localizedCapitalized
, localizedLowercased
and localizedUppercased
:
// "JÉRÔME"
let uppercased = DatabaseFunction.uppercase
try String.fetchOne(db, sql: "SELECT \(uppercased.name)('Jérôme')")
Those unicode-aware string functions are also readily available in the query interface:
Player.select(nameColumn.uppercased)
SQLite compares strings in many occasions: when you sort rows according to a string column, or when you use a comparison operator such as =
and <=
.
The comparison result comes from a collating function, or collation. SQLite comes with three built-in collations that do not support Unicode: binary, nocase, and rtrim.
GRDB comes with five extra collations that leverage unicode-aware comparisons based on the standard Swift String comparison functions and operators:
unicodeCompare
(uses the built-in<=
and==
Swift operators)caseInsensitiveCompare
localizedCaseInsensitiveCompare
localizedCompare
localizedStandardCompare
A collation can be applied to a table column. All comparisons involving this column will then automatically trigger the comparison function:
try db.create(table: "player") { t in
// Guarantees case-insensitive email unicity
t.column("email", .text).unique().collate(.nocase)
// Sort names in a localized case insensitive way
t.column("name", .text).collate(.localizedCaseInsensitiveCompare)
}
// Players are sorted in a localized case insensitive way:
let players = try Player.order(nameColumn).fetchAll(db)
Warning: SQLite requires host applications to provide the definition of any collation other than binary, nocase and rtrim. When a database file has to be shared or migrated to another SQLite library of platform (such as the Android version of your application), make sure you provide a compatible collation.
If you can't or don't want to define the comparison behavior of a column (see warning above), you can still use an explicit collation in SQL requests and in the query interface:
let collation = DatabaseCollation.localizedCaseInsensitiveCompare
let players = try Player.fetchAll(db,
sql: "SELECT * FROM player ORDER BY name COLLATE \(collation.name))")
let players = try Player.order(nameColumn.collating(collation)).fetchAll(db)
You can also define your own collations:
let collation = DatabaseCollation("customCollation") { (lhs, rhs) -> NSComparisonResult in
// return the comparison of lhs and rhs strings.
}
// Make the collation available to a database connection
var config = Configuration()
config.prepareDatabase { db in
db.add(collation: collation)
}
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config)
Both SQLite and GRDB use non-essential memory that help them perform better.
You can reclaim this memory with the releaseMemory
method:
// Release as much memory as possible.
dbQueue.releaseMemory()
dbPool.releaseMemory()
This method blocks the current thread until all current database accesses are completed, and the memory collected.
Warning: If
DatabasePool.releaseMemory()
is called while a long read is performed concurrently, then no other read access will be possible until this long read has completed, and the memory has been released. If this does not suit your application needs, look for the asynchronous options below:
You can release memory in an asynchronous way as well:
// On a DatabaseQueue
dbQueue.asyncWriteWithoutTransaction { db in
db.releaseMemory()
}
// On a DatabasePool
dbPool.releaseMemoryEventually()
DatabasePool.releaseMemoryEventually()
does not block the current thread, and does not prevent concurrent database accesses. In exchange for this convenience, you don't know when memory has been freed.
The iOS operating system likes applications that do not consume much memory.
Database queues and pools automatically free non-essential memory when the application receives a memory warning, and when the application enters background.
You can opt out of this automatic memory management:
var config = Configuration()
config.automaticMemoryManagement = false
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config) // or DatabasePool
- How do I create a database in my application?
- How do I open a database stored as a resource of my application?
- How do I close a database connection?
- How do I monitor the duration of database statements execution?
- What Are Experimental Features?
- Does GRDB support library evolution and ABI stability?
- How do I filter records and only keep those that are associated to another record?
- How do I filter records and only keep those that are NOT associated to another record?
- How do I select only one column of an associated record?
- Generic parameter 'T' could not be inferred
- Mutation of captured var in concurrently-executing code
- SQLite error 1 "no such column"
- SQLite error 10 "disk I/O error", SQLite error 23 "not authorized"
- SQLite error 21 "wrong number of statement arguments" with LIKE queries
- ⬆️ FAQ
- How do I create a database in my application?
- How do I open a database stored as a resource of my application?
- How do I close a database connection?
First choose a proper location for the database file. Document-based applications will let the user pick a location. Apps that use the database as a global storage will prefer the Application Support directory.
The sample code below creates or opens a database file inside its dedicated directory (a recommended practice). On the first run, a new empty database file is created. On subsequent runs, the database file already exists, so it just opens a connection:
// HOW TO create an empty database, or open an existing database file
// Create the "Application Support/MyDatabase" directory
let fileManager = FileManager.default
let appSupportURL = try fileManager.url(
for: .applicationSupportDirectory, in: .userDomainMask,
appropriateFor: nil, create: true)
let directoryURL = appSupportURL.appendingPathComponent("MyDatabase", isDirectory: true)
try fileManager.createDirectory(at: directoryURL, withIntermediateDirectories: true)
// Open or create the database
let databaseURL = directoryURL.appendingPathComponent("db.sqlite")
let dbQueue = try DatabaseQueue(path: databaseURL.path)
Open a read-only connection to your resource:
// HOW TO open a read-only connection to a database resource
// Get the path to the database resource.
if let dbPath = Bundle.main.path(forResource: "db", ofType: "sqlite") {
// If the resource exists, open a read-only connection.
// Writes are disallowed because resources can not be modified.
var config = Configuration()
config.readonly = true
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config)
} else {
// The database resource can not be found.
// Fix your setup, or report the problem to the user.
}
Database connections are automatically closed when DatabaseQueue
or DatabasePool
instances are deinitialized.
If the correct execution of your program depends on precise database closing, perform an explicit call to close()
. This method may fail and create zombie connections, so please check its detailed documentation.
When you want to debug a request that does not deliver the expected results, you may want to print the SQL that is actually executed.
You can compile the request into a prepared Statement
:
try dbQueue.read { db in
let request = Player.filter(Column("email") == "[email protected]")
let statement = try request.makePreparedRequest(db).statement
print(statement) // SELECT * FROM player WHERE email = ?
print(statement.arguments) // ["[email protected]"]
}
Another option is to setup a tracing function that prints out the executed SQL requests. For example, provide a tracing function when you connect to the database:
// Prints all SQL statements
var config = Configuration()
config.prepareDatabase { db in
db.trace { print($0) }
}
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config)
try dbQueue.read { db in
// Prints "SELECT * FROM player WHERE email = ?"
let players = try Player.filter(Column("email") == "[email protected]").fetchAll(db)
}
If you want to see statement arguments such as '[email protected]'
in the logged statements, make statement arguments public.
Note: the generated SQL may change between GRDB releases, without notice: don't have your application rely on any specific SQL output.
- ⬆️ FAQ
- How do I monitor the duration of database statements execution?
- What Are Experimental Features?
- Does GRDB support library evolution and ABI stability?
Use the trace(options:_:)
method, with the .profile
option:
var config = Configuration()
config.prepareDatabase { db in
db.trace(options: .profile) { event in
// Prints all SQL statements with their duration
print(event)
// Access to detailed profiling information
if case let .profile(statement, duration) = event, duration > 0.5 {
print("Slow query: \(statement.sql)")
}
}
}
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config)
try dbQueue.read { db in
let players = try Player.filter(Column("email") == "[email protected]").fetchAll(db)
// Prints "0.003s SELECT * FROM player WHERE email = ?"
}
If you want to see statement arguments such as '[email protected]'
in the logged statements, make statement arguments public.
Since GRDB 1.0, all backwards compatibility guarantees of semantic versioning apply: no breaking change will happen until the next major version of the library.
There is an exception, though: experimental features, marked with the "🔥 EXPERIMENTAL" badge. Those are advanced features that are too young, or lack user feedback. They are not stabilized yet.
Those experimental features are not protected by semantic versioning, and may break between two minor releases of the library. To help them becoming stable, your feedback is greatly appreciated.
No, GRDB does not support library evolution and ABI stability. The only promise is API stability according to semantic versioning, with an exception for experimental features.
Yet, GRDB can be built with the "Build Libraries for Distribution" Xcode option (BUILD_LIBRARY_FOR_DISTRIBUTION
), so that you can build binary frameworks at your convenience.
- ⬆️ FAQ
- How do I filter records and only keep those that are associated to another record?
- How do I filter records and only keep those that are NOT associated to another record?
- How do I select only one column of an associated record?
Let's say you have two record types, Book
and Author
, and you want to only fetch books that have an author, and discard anonymous books.
We start by defining the association between books and authors:
struct Book: TableRecord {
...
static let author = belongsTo(Author.self)
}
struct Author: TableRecord {
...
}
And then we can write our request and only fetch books that have an author, discarding anonymous ones:
let books: [Book] = try dbQueue.read { db in
// SELECT book.* FROM book
// JOIN author ON author.id = book.authorID
let request = Book.joining(required: Book.author)
return try request.fetchAll(db)
}
Note how this request does not use the filter
method. Indeed, we don't have any condition to express on any column. Instead, we just need to "require that a book can be joined to its author".
See How do I filter records and only keep those that are NOT associated to another record? below for the opposite question.
Let's say you have two record types, Book
and Author
, and you want to only fetch anonymous books that do not have any author.
We start by defining the association between books and authors:
struct Book: TableRecord {
...
static let author = belongsTo(Author.self)
}
struct Author: TableRecord {
...
}
And then we can write our request and only fetch anonymous books that don't have any author:
let books: [Book] = try dbQueue.read { db in
// SELECT book.* FROM book
// LEFT JOIN author ON author.id = book.authorID
// WHERE author.id IS NULL
let authorAlias = TableAlias()
let request = Book
.joining(optional: Book.author.aliased(authorAlias))
.filter(!authorAlias.exists)
return try request.fetchAll(db)
}
This request uses a TableAlias in order to be able to filter on the eventual associated author. We make sure that the Author.primaryKey
is nil, which is another way to say it does not exist: the book has no author.
See How do I filter records and only keep those that are associated to another record? above for the opposite question.
Let's say you have two record types, Book
and Author
, and you want to fetch all books with their author name, but not the full associated author records.
We start by defining the association between books and authors:
struct Book: Decodable, TableRecord {
...
static let author = belongsTo(Author.self)
}
struct Author: Decodable, TableRecord {
...
enum Columns {
static let name = Column(CodingKeys.name)
}
}
And then we can write our request and the ad-hoc record that decodes it:
struct BookInfo: Decodable, FetchableRecord {
var book: Book
var authorName: String? // nil when the book is anonymous
static func all() -> QueryInterfaceRequest<BookInfo> {
// SELECT book.*, author.name AS authorName
// FROM book
// LEFT JOIN author ON author.id = book.authorID
let authorName = Author.Columns.name.forKey(CodingKeys.authorName)
return Book
.annotated(withOptional: Book.author.select(authorName))
.asRequest(of: BookInfo.self)
}
}
let bookInfos: [BookInfo] = try dbQueue.read { db in
BookInfo.all().fetchAll(db)
}
By defining the request as a static method of BookInfo, you have access to the private CodingKeys.authorName
, and a compiler-checked SQL column name.
By using the annotated(withOptional:)
method, you append the author name to the top-level selection that can be decoded by the ad-hoc record.
By using asRequest(of:)
, you enhance the type-safety of your request.
Sometimes it looks that a ValueObservation does not notify the changes you expect.
There may be four possible reasons for this:
- The expected changes were not committed into the database.
- The expected changes were committed into the database, but were quickly overwritten.
- The observation was stopped.
- The observation does not track the expected database region.
To answer the first two questions, look at SQL statements executed by the database. This is done when you open the database connection:
// Prints all SQL statements
var config = Configuration()
config.prepareDatabase { db in
db.trace { print("SQL: \($0)") }
}
let dbQueue = try DatabaseQueue(path: dbPath, configuration: config)
If, after that, you are convinced that the expected changes were committed into the database, and not overwritten soon after, trace observation events:
let observation = ValueObservation
.tracking { db in ... }
.print() // <- trace observation events
let cancellable = observation.start(...)
Look at the observation logs which start with cancel
or failure
: maybe the observation was cancelled by your app, or did fail with an error.
Look at the observation logs which start with value
: make sure, again, that the expected value was not actually notified, then overwritten.
Finally, look at the observation logs which start with tracked region
. Does the printed database region cover the expected changes?
For example:
empty
: The empty region, which tracks nothing and never triggers the observation.player(*)
: The fullplayer
tableplayer(id,name)
: Theid
andname
columns of theplayer
tableplayer(id,name)[1]
: Theid
andname
columns of the row with id 1 in theplayer
tableplayer(*),team(*)
: Both the fullplayer
andteam
tables
If you happen to use the ValueObservation.trackingConstantRegion(_:)
method and see a mismatch between the tracked region and your expectation, then change the definition of your observation by using tracking(_:)
. You should witness that the logs which start with tracked region
now evolve in order to include the expected changes, and that you get the expected notifications.
If after all those steps (thanks you!), your observation is still failing you, please open an issue and provide a minimal reproducible example!
- ⬆️ FAQ
- Generic parameter 'T' could not be inferred
- Mutation of captured var in concurrently-executing code
- SQLite error 1 "no such column"
- SQLite error 10 "disk I/O error", SQLite error 23 "not authorized"
- SQLite error 21 "wrong number of statement arguments" with LIKE queries
You may get this error when using the read
and write
methods of database queues and pools:
// Generic parameter 'T' could not be inferred
let string = try dbQueue.read { db in
let result = try String.fetchOne(db, ...)
return result
}
This is a limitation of the Swift compiler.
The general workaround is to explicitly declare the type of the closure result:
// General Workaround
let string = try dbQueue.read { db -> String? in
let result = try String.fetchOne(db, ...)
return result
}
You can also, when possible, write a single-line closure:
// Single-line closure workaround:
let string = try dbQueue.read { db in
try String.fetchOne(db, ...)
}
The insert
and save
persistence methods can trigger a compiler error in async contexts:
var player = Player(id: nil, name: "Arthur")
try await dbWriter.write { db in
// Error: Mutation of captured var 'player' in concurrently-executing code
try player.insert(db)
}
print(player.id) // A non-nil id
When this happens, prefer the inserted
and saved
methods instead:
// OK
var player = Player(id: nil, name: "Arthur")
player = try await dbWriter.write { [player] db in
return try player.inserted(db)
}
print(player.id) // A non-nil id
This error message is self-explanatory: do check for misspelled or non-existing column names.
However, sometimes this error only happens when an app runs on a recent operating system (iOS 14+, Big Sur+, etc.) The error does not happen with previous ones.
When this is the case, there are two possible explanations:
-
Maybe a column name is really misspelled or missing from the database schema.
To find it, check the SQL statement that comes with the DatabaseError.
-
Maybe the application is using the character
"
instead of the single quote'
as the delimiter for string literals in raw SQL queries. Recent versions of SQLite have learned to tell about this deviation from the SQL standard, and this is why you are seeing this error.For example: this is not standard SQL:
UPDATE player SET name = "Arthur"
.The standard version is:
UPDATE player SET name = 'Arthur'
.It just happens that old versions of SQLite used to accept the former, non-standard version. Newer versions are able to reject it with an error.
The fix is to change the SQL statements run by the application: replace
"
with'
in your string literals.It may also be time to learn about statement arguments and SQL injection:
let name: String = ... // NOT STANDARD (double quote) try db.execute(sql: """ UPDATE player SET name = "\(name)" """) // STANDARD, BUT STILL NOT RECOMMENDED (single quote) try db.execute(sql: "UPDATE player SET name = '\(name)'") // STANDARD, AND RECOMMENDED (statement arguments) try db.execute(sql: "UPDATE player SET name = ?", arguments: [name])
For more information, see Double-quoted String Literals Are Accepted, and Configuration.acceptsDoubleQuotedStringLiterals.
Those errors may be the sign that SQLite can't access the database due to data protection.
When your application should be able to run in the background on a locked device, it has to catch this error, and, for example, wait for UIApplicationDelegate.applicationProtectedDataDidBecomeAvailable(_:) or UIApplicationProtectedDataDidBecomeAvailable notification and retry the failed database operation.
do {
try ...
} catch DatabaseError.SQLITE_IOERR, DatabaseError.SQLITE_AUTH {
// Handle possible data protection error
}
This error can also be prevented altogether by using a more relaxed file protection.
You may get the error "wrong number of statement arguments" when executing a LIKE query similar to:
let name = textField.text
let players = try dbQueue.read { db in
try Player.fetchAll(db, sql: "SELECT * FROM player WHERE name LIKE '%?%'", arguments: [name])
}
The problem lies in the '%?%'
pattern.
SQLite only interprets ?
as a parameter when it is a placeholder for a whole value (int, double, string, blob, null). In this incorrect query, ?
is just a character in the '%?%'
string: it is not a query parameter, and is not processed in any way. See https://www.sqlite.org/lang_expr.html#varparam for more information about SQLite parameters.
To fix the error, you can feed the request with the pattern itself, instead of the name:
let name = textField.text
let players: [Player] = try dbQueue.read { db in
let pattern = "%\(name)%"
return try Player.fetchAll(db, sql: "SELECT * FROM player WHERE name LIKE ?", arguments: [pattern])
}
- The Documentation is full of GRDB snippets.
- Demo Applications
- Open
GRDB.xcworkspace
: it contains GRDB-enabled playgrounds to play with. - groue/SortedDifference: How to synchronize a database table with a JSON payload
Thanks
- Pierlis, where we write great software.
- @alextrob, @alexwlchan, @bellebethcooper, @bfad, @cfilipov, @charlesmchen-signal, @Chiliec, @chrisballinger, @darrenclark, @davidkraus, @eburns-vmware, @felixscheinost, @fpillet, @gcox, @GetToSet, @gjeck, @guidedways, @gusrota, @haikusw, @hartbit, @holsety, @jroselightricks, @kdubb, @kluufger, @KyleLeneau, @layoutSubviews, @mallman, @MartinP7r, @Marus, @mattgallagher, @MaxDesiatov, @michaelkirk-signal, @mtancock, @pakko972, @peter-ss, @pierlo, @pocketpixels, @pp5x, @professordeng, @robcas3, @runhum, @sberrevoets, @schveiguy, @SD10, @sobri909, @sroddy, @steipete, @swiftlyfalling, @Timac, @tternes, @valexa, @wuyuehyang, @ZevEisenberg, and @zmeyc for their contributions, help, and feedback on GRDB.
- @aymerick and @kali because SQL.
- ccgus/fmdb for its excellency.
URIs don't change: people change them.
This chapter was renamed to Embedding SQL in Query Interface Requests.
This chapter has moved.
This chapter has moved.
This chapter has moved.
This chapter has been renamed Record Comparison.
This chapter has moved.
Custom Value Types conform to the DatabaseValueConvertible
protocol.
This chapter has been renamed Beyond FetchableRecord.
This chapter was replaced with Persistence Callbacks.
This chapter has moved.
This chapter has moved.
This chapter has moved.
This chapter has moved.
This chapter has moved.
This chapter was removed. See the references of DatabaseReader and DatabaseWriter.
This chapter has been renamed Data, Date, and UUID Coding Strategies.
This chapter has been superseded by the Sharing a Database guide.
This chapter has moved.
FTS5 is enabled by default since GRDB 6.7.0.
FetchedRecordsController has been removed in GRDB 5.
The Database Observation chapter describes the other ways to observe the database.
This chapter has moved.
This chapter has moved.
This chapter was replaced with the documentation of splittingRowAdapters(columnCounts:).
See Records and the Query Interface.
This chapter has moved.
This chapter has moved.
This protocol has been renamed PersistableRecord in GRDB 3.0.
This error was renamed to RecordError.
This chapter has moved.
The Record
class is a legacy GRDB type. Since GRDB 7, it is not recommended to define record types by subclassing the Record
class.
This chapter has moved.
This protocol has been renamed FetchableRecord in GRDB 3.0.
This protocol has been renamed TableRecord in GRDB 3.0.
This chapter has moved.
This chapter has moved.
This chapter has moved.
This chapter has moved.
This chapter has moved.
This chapter has been superseded by ValueObservation and DatabaseRegionObservation.