Fix ~string.IsNullOrEmpty~ string.Length mapping for SQL CE/MSSQL

Source/LinqToDB/Linq/Expressions.cs

@@ -588,7 +588,7 @@ public void SetInfo(MappingSchema mappingSchema)
 
  #region string
 
- { M(() => "".Length ), N(() => L<string,int> ((string obj) => Sql.Length(obj)!.Value)) },
+ { M(() => "".Length ), N(() => L<string,int> ((string obj) => Sql.StringLength(obj)!.Value)) },
  { M(() => "".Substring (0) ), N(() => L<string?,int,string?> ((string? obj,int p0) => Sql.Substring(obj, p0 + 1, obj!.Length - p0))) },
  { M(() => "".Substring (0,0) ), N(() => L<string?,int,int,string?> ((string? obj,int p0,int p1) => Sql.Substring(obj, p0 + 1, p1))) },
  { M(() => "".IndexOf ("") ), N(() => L<string,string,int> ((string obj,string p0) => p0.Length == 0 ? 0 : (Sql.CharIndex(p0, obj)! .Value) - 1)) },

Source/LinqToDB/Sql/Sql.cs

@@ -1,22 +1,24 @@
 using System;
 using System.Collections.Generic;
 using System.Data.Linq;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq.Expressions;
 using System.Reflection;
 
 using JetBrains.Annotations;
+
 using PN = LinqToDB.ProviderName;
 
 // ReSharper disable CheckNamespace
 // ReSharper disable RedundantNameQualifier
 
 namespace LinqToDB
 {
- using Mapping;
  using Expressions;
  using Linq;
- using SqlQuery;
  using LinqToDB.Common;
+ using Mapping;
+ using SqlQuery;
 
  [PublicAPI]
  public static partial class Sql
@@ -269,7 +271,7 @@ public static Guid NewGuid()
 
  [CLSCompliant(false)]
  [Function("Convert", 0, 1, ServerSideOnly = true, IsPure = true, IsNullable = IsNullableType.SameAsSecondParameter)]
- [Function(PseudoFunctions.CONVERT, 2, 3, 1, ServerSideOnly = true, IsPure = true, IsNullable = IsNullableType.SameAsSecondParameter, Configuration = ProviderName.ClickHouse)]
+ [Function(PseudoFunctions.CONVERT, 2, 3, 1, ServerSideOnly = true, IsPure = true, IsNullable = IsNullableType.SameAsSecondParameter, Configuration = PN.ClickHouse)]
  public static TTo Convert<TTo,TFrom>(TTo to, TFrom from)
  {
  return Common.ConvertTo<TTo>.From(from);
@@ -285,7 +287,7 @@ public static TTo Convert<TTo, TFrom>(TTo to, TFrom from, int format)
  // TODO: v5 remove. bltoolkit legacy which duplicates Convert function above (without ServerSideOnly, but it shouldn't matter)
  [CLSCompliant(false)]
  [Function("Convert", 0, 1, IsPure = true, IsNullable = IsNullableType.SameAsSecondParameter)]
- [Function(PseudoFunctions.CONVERT, 2, 3, 1, ServerSideOnly = true, IsPure = true, IsNullable = IsNullableType.SameAsSecondParameter, Configuration = ProviderName.ClickHouse)]
+ [Function(PseudoFunctions.CONVERT, 2, 3, 1, ServerSideOnly = true, IsPure = true, IsNullable = IsNullableType.SameAsSecondParameter, Configuration = PN.ClickHouse)]
  public static TTo Convert2<TTo,TFrom>(TTo to, TFrom from)
  {
  return Common.ConvertTo<TTo>.From(from);
@@ -383,6 +385,14 @@ public static TTo From<TFrom>(TFrom obj)
 
  #region String Functions
 
+ /// <summary>
+ /// Returns string length in characters by calling corresponding database function as-is.
+ /// Could result in unexpected results due to non-standard behavior of some databases.
+ /// E.g. see LEN function notes for SQL CE or MSSQL databases.
+ /// For more standard behavior look at <see cref="StringLength(string?)"/> function.
+ /// </summary>
+ /// <param name="str">String value.</param>
+ /// <returns>String length or <c>null</c> for NULL input.</returns>
  [Function ( PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
  [Function (PN.Access, "Len", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
  [Function (PN.Firebird, "Char_Length", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
@@ -393,11 +403,41 @@ public static TTo From<TFrom>(TFrom obj)
  [Function (PN.Informix, "CHAR_LENGTH", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
  [Function (PN.ClickHouse, "CHAR_LENGTH", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
  [Expression(PN.DB2LUW, "CHARACTER_LENGTH({0},CODEUNITS32)", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
+ [return: NotNullIfNotNull(nameof(str))]
  public static int? Length(string? str)
  {
  return str?.Length;
  }
 
+ /// <summary>
+ /// Returns string length in characters by calling corresponding database function.
+ /// Compared to <see cref="Length(string?)"/> function, it tries to calculate length in same way as <see cref="string.Length"/> property
+ /// for databases with non-standard length functions.
+ /// E.g. see LEN function notes for SQL CE or MSSQL databases.
+ /// Known issues with empty string:
+ /// <list type="bullet">
+ /// <item>Oracle treats '' as NULL and returns NULL instead of 1</item>
+ /// <item>Sybase ASE treats '' as ' ' and returns 1 instead of 1</item>
+ /// </list>
+ /// </summary>
+ /// <param name="str">String value.</param>
+ /// <returns>String length or <c>null</c> for NULL input.</returns>
+ [Function ( "Length", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
+ [Function (PN.Access, "Len", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
+ [Function (PN.Firebird, "Char_Length", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
+ [Expression(PN.SqlServer, "LEN(REPLACE({0},' ','.'))", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
+ [Expression(PN.SqlCe, "LEN(REPLACE({0},' ','.'))", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
+ [Function (PN.Sybase, "Len", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
+ [Function (PN.MySql, "Char_Length", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
+ [Function (PN.Informix, "CHAR_LENGTH", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
+ [Function (PN.ClickHouse, "CHAR_LENGTH", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
+ [Expression(PN.DB2LUW, "CHARACTER_LENGTH({0},CODEUNITS32)", PreferServerSide = true, IsNullable = IsNullableType.SameAsFirstParameter)]
+ [return: NotNullIfNotNull(nameof(str))]
+ public static int? StringLength(string? str)
+ {
+ return str?.Length;
+ }
+
  [Function ( PreferServerSide = true, IsNullable = IsNullableType.IfAnyParameterNullable)]
  [Function (PN.Access, "Mid", PreferServerSide = true, IsNullable = IsNullableType.IfAnyParameterNullable)]
  [Function (PN.DB2, "Substr", PreferServerSide = true, IsNullable = IsNullableType.IfAnyParameterNullable)]

Tests/Linq/Linq/StringFunctionTests.cs

@@ -1449,6 +1449,129 @@ public void IsNullOrEmpty2([DataSources] string context)
  }
  }
 
+ public sealed class IsNullOrEmptyTable
+ {
+ public int Id { get; set; }
+ public string? Value { get; set; }
+ }
+
+ [Test(Description = "https://github.com/linq2db/linq2db/issues/4138")]
+ public void IsNullOrEmpty3([DataSources] string context)
+ {
+ using var db = GetDataContext(context);
+ using var t = db.CreateLocalTable(new[]
+ {
+ new IsNullOrEmptyTable() { Id = 1, Value = " " },
+ new IsNullOrEmptyTable() { Id = 2, Value = "" },
+ });
+
+ var results = (from p in t where string.IsNullOrEmpty(p.Value) select p).ToList();
+
+ if (context.IsAnyOf(TestProvName.AllSybase))
+ {
+ Assert.That(results, Is.Empty);
+ }
+ else
+ {
+ Assert.That(results.Count, Is.EqualTo(1));
+ Assert.That(results[0].Id, Is.EqualTo(2));
+ }
+ }
+
+ [Test(Description = "https://github.com/linq2db/linq2db/issues/4138")]
+ public void IsNullOrEmptySybase([IncludeDataSources(true, TestProvName.AllSybase)] string context)
+ {
+ // sybase doesn't have empty string concept
+ // empty string replaced with ' '
+ // https://stackoverflow.com/questions/52284561
+ using var db = GetDataContext(context);
+ using var t = db.CreateLocalTable(new[]
+ {
+ new IsNullOrEmptyTable() { Id = 1, Value = " " },
+ new IsNullOrEmptyTable() { Id = 2, Value = "" },
+ });
+
+ var results = (from p in t where string.IsNullOrEmpty(p.Value) select p).ToList();
+
+ Assert.That(results, Is.Empty);
+ }
+
+ // Sybase: https://stackoverflow.com/questions/52284561
+ [Test(Description = "https://github.com/linq2db/linq2db/issues/4138")]
+ public void StringLength1([DataSources] string context)
+ {
+ using var db = GetDataContext(context);
+ using var t = db.CreateLocalTable(new[]
+ {
+ new IsNullOrEmptyTable() { Id = 1, Value = " " },
+ new IsNullOrEmptyTable() { Id = 2, Value = "" },
+ });
+
+ var results = (from p in t where p.Value!.Length == 0 select p).ToList();
+
+ if (context.IsAnyOf(TestProvName.AllOracle, TestProvName.AllSybase))
+ {
+ Assert.That(results, Is.Empty);
+ }
+ else
+ {
+ Assert.That(results.Count, Is.EqualTo(1));
+ Assert.That(results[0].Id, Is.EqualTo(2));
+ }
+ }
+
+ // Sybase: https://stackoverflow.com/questions/52284561
+ [Test(Description = "https://github.com/linq2db/linq2db/issues/4138")]
+ public void StringLength2([DataSources] string context)
+ {
+ using var db = GetDataContext(context);
+ using var t = db.CreateLocalTable(new[]
+ {
+ new IsNullOrEmptyTable() { Id = 1, Value = " " },
+ new IsNullOrEmptyTable() { Id = 2, Value = "" },
+ });
+
+ var results = (from p in t where p.Value!.Length == 3 select p).ToList();
+
+ if (context.IsAnyOf(TestProvName.AllSybase))
+ {
+ // sybase:
+ // - trims trailing whitespaces in storage (1)
+ // - '' replaced with ' '
+ Assert.That(results, Is.Empty);
+ }
+ else
+ {
+ Assert.That(results.Count, Is.EqualTo(1));
+ Assert.That(results[0].Id, Is.EqualTo(1));
+ }
+ }
+
+ // Sybase: https://stackoverflow.com/questions/52284561
+ [Test(Description = "https://github.com/linq2db/linq2db/issues/4138")]
+ public void StringLength3([DataSources] string context)
+ {
+ using var db = GetDataContext(context);
+ using var t = db.CreateLocalTable(new[]
+ {
+ new IsNullOrEmptyTable() { Id = 1, Value = "x " },
+ new IsNullOrEmptyTable() { Id = 2, Value = "xxxx " },
+ });
+
+ var results = (from p in t where p.Value!.Length == 4 select p).ToList();
+
+ Assert.That(results.Count, Is.EqualTo(1));
+ if (context.IsAnyOf(TestProvName.AllSybase))
+ {
+ // Sybase removes spaces on insert (?)
+ Assert.That(results[0].Id, Is.EqualTo(2));
+ }
+ else
+ {
+ Assert.That(results[0].Id, Is.EqualTo(1));
+ }
+ }
+
  [Table]
  sealed class CollatedTable
  {