fix(plugin-postgres): Fix Timestamp values in JDBC connectors

[tdcmeehan]

Description

Fix timestamp handling in MySQL and PostgreSQL JDBC connectors when legacy_timestamp=false. Timestamps are now correctly stored and read as wall-clock values without timezone conversion.

Motivation and Context

When legacy_timestamp=false (the default), the JDBC connectors were incorrectly applying JVM timezone conversion on both reads and writes. This caused:

• Values inserted directly into the database were read with incorrect timezone conversion
• Values inserted via Presto were written with incorrect timezone conversion

The fix adds UTC calendar parameter for non-legacy timestamp mappings so they use wall-clock semantics.

Impact

Fixes data corruption for users with non-UTC JVM timezone.

Test Plan

Included unit tests.

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• Please make sure your submission complies with our contributing guide, in particular code style and commit standards.
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• Documented new properties (with its default value), SQL syntax, functions, or other functionality.
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• Adequate tests were added if applicable.
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Release Notes

== RELEASE NOTES ==

MySQL Connector Changes
* Fix timestamp handling when ``legacy_timestamp`` is disabled. Timestamp values are now correctly stored and retrieved as wall-clock times without timezone conversion. Previously, values were incorrectly converted using the JVM timezone, causing data corruption.

PostgreSQL Connector Changes
* Fix timestamp handling when ``legacy_timestamp`` is disabled. Timestamp values are now correctly stored and retrieved as wall-clock times without timezone conversion. Previously, values were incorrectly converted using the JVM timezone, causing data corruption.

[sourcery-ai]

Reviewer's Guide

This PR enforces UTC-based timestamp handling in JDBC connectors by introducing an explicit UTC calendar for read/write operations, preserves legacy behavior via new mappings toggled by the legacy_timestamp session property, propagates this flag through connector APIs, and adds rigorous tests validating timestamp/datetime storage and retrieval in both modes for PostgreSQL and MySQL.

Sequence diagram for timestamp read/write with legacy flag propagation

sequenceDiagram
    participant "User Query (Presto)"
    participant "ConnectorSession"
    participant "JdbcClient"
    participant "StandardColumnMappings"
    participant "Database (JDBC)"
    "User Query (Presto)"->>"ConnectorSession": Execute query with session
    "ConnectorSession"->>"JdbcClient": Request toReadMapping / toWriteMapping with session
    "JdbcClient"->>"StandardColumnMappings": Pass legacyTimestamp flag from session
    alt legacyTimestamp = true
        "StandardColumnMappings"->>"Database (JDBC)": Use legacy mapping (no UTC calendar)
    else legacyTimestamp = false
        "StandardColumnMappings"->>"Database (JDBC)": Use UTC calendar for timestamp
    end

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ER diagram for timestamp mapping modes in session

erDiagram
    CONNECTOR_SESSION {
        bool legacyTimestamp
    }
    STANDARD_COLUMN_MAPPINGS {
        method timestampReadMapping()
        method timestampReadMappingLegacy()
        method timestampWriteMapping(TimestampType)
        method timestampWriteMappingLegacy(TimestampType)
    }
    CONNECTOR_SESSION ||--o| STANDARD_COLUMN_MAPPINGS : "uses legacyTimestamp to select mapping"

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Class diagram for updated timestamp mapping in JDBC connectors

classDiagram
    class StandardColumnMappings {
        +booleanReadMapping()
        +timeWriteMapping()
        +timestampReadMapping()
        +timestampReadMappingLegacy() <<deprecated>>
        +timestampWriteMapping(TimestampType)
        +timestampWriteMappingLegacy(TimestampType) <<deprecated>>
        +uuidWriteMapping()
        +jdbcTypeToReadMapping(JdbcTypeHandle)
        +prestoTypeToWriteMapping(ConnectorSession, Type)
    }
    class BaseJdbcClient {
        +getColumns(ConnectorSession, JdbcTableHandle)
        +toPrestoType(ConnectorSession, JdbcTypeHandle)
        +toWriteMapping(ConnectorSession, Type)
    }
    class JdbcClient {
        +toPrestoType(ConnectorSession, JdbcTypeHandle)
        +toWriteMapping(ConnectorSession, Type)
    }
    class JdbcPageSink {
        +JdbcPageSink(ConnectorSession, JdbcOutputTableHandle, JdbcClient)
    }
    StandardColumnMappings <|-- BaseJdbcClient
    JdbcClient <|-- BaseJdbcClient
    JdbcClient <|-- JdbcPageSink
    BaseJdbcClient o-- StandardColumnMappings
    JdbcPageSink o-- JdbcClient

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File-Level Changes

Change	Details	Files
Introduce UTC calendar and legacy mappings in StandardColumnMappings to remove timezone drift	Add UTC_CALENDAR constant Update timestampReadMapping to use resultSet.getTimestamp with UTC_CALENDAR Deprecate old timestampReadMapping as timestampReadMappingLegacy Update timestampWriteMapping to setTimestamp with UTC_CALENDAR Add deprecated timestampWriteMappingLegacy	presto-base-jdbc/src/main/java/com/facebook/presto/plugin/jdbc/mapping/StandardColumnMappings.java
Propagate legacy_timestamp flag through write mapping selection in JDBC client APIs	Change prestoTypeToWriteMapping signature to accept ConnectorSession and branch on legacy flag Update BaseJdbcClient.toPrestoType to choose legacy or UTC read mapping for TIMESTAMP Change BaseJdbcClient.toWriteMapping to accept session and select mapping accordingly Modify JdbcClient interface to pass ConnectorSession into toWriteMapping Update JdbcPageSink to supply session when resolving write functions	presto-base-jdbc/src/main/java/com/facebook/presto/plugin/jdbc/BaseJdbcClient.java presto-base-jdbc/src/main/java/com/facebook/presto/plugin/jdbc/JdbcClient.java presto-base-jdbc/src/main/java/com/facebook/presto/plugin/jdbc/JdbcPageSink.java
Update TestJdbcQueryBuilder to use UTC calendar and Instant for timestamp tests	Add UTC_CALENDAR constant in test class Use resultSet.getTimestamp with UTC_CALENDAR instead of getObject Revise toTimestamp helper to generate UTC-based Timestamp via Instant	presto-base-jdbc/src/test/java/com/facebook/presto/plugin/jdbc/TestJdbcQueryBuilder.java
Add detailed storage verification tests for timestamps/datetimes in Postgres and MySQL connectors	Rename and expand timestamp test in TestPostgreSqlTypeMapping to two methods covering legacy and non-legacy modes Add JDBC-based assertions verifying wall-clock storage and Presto retrieval Mirror similar changes in TestMySqlTypeMapping for DATETIME with legacy and UTC sessions	presto-postgresql/src/test/java/com/facebook/presto/plugin/postgresql/TestPostgreSqlTypeMapping.java presto-mysql/src/test/java/com/facebook/presto/plugin/mysql/TestMySqlTypeMapping.java

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[sourcery-ai]

Hey there - I've reviewed your changes and they look great!

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location> `presto-base-jdbc/src/main/java/com/facebook/presto/plugin/jdbc/mapping/StandardColumnMappings.java:97` </location>
<code_context>
     private StandardColumnMappings() {}

     private static final ISOChronology UTC_CHRONOLOGY = ISOChronology.getInstanceUTC();
+    private static final Calendar UTC_CALENDAR = Calendar.getInstance(TimeZone.getTimeZone("UTC"));

     public static ReadMapping booleanReadMapping()
</code_context>

<issue_to_address>
**issue (bug_risk):** Consider using a thread-safe alternative to Calendar for UTC handling.

Since Calendar is mutable, sharing a static instance can cause concurrency issues. Use java.time APIs, instantiate Calendar per use, or clearly document thread-safety assumptions.
</issue_to_address>

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[lithinwxd]

What happens if the user session and server are in different zone . what happens if we set session timezone key as "Asia/kolkata" for same scenario?

[tdcmeehan]

Done

[lithinwxd]

Looks good . Thank you !

[tdcmeehan]

@sourcery-ai summary

[BryanCutler]

LGTM, very thorough tests. Thanks @tdcmeehan !