sink/mysql: align DDL time defaults with origin_default #3991

haiboumich · 2026-01-13T03:29:10Z

What problem does this PR solve?

DDL statements that add columns with CURRENT_TIMESTAMP-style defaults can produce different initial values downstream if the DDL is applied later or in a different time zone. This PR ensures TiCDC uses the upstream-evaluated default when executing those DDLs.

Issue Number: close #4007

What is changed and how it works?

Parse DDL statements to detect CURRENT_TIMESTAMP/NOW/LOCALTIME/LOCALTIMESTAMP defaults.
Use the column origin_default from TableInfo to set session @@timestamp before executing the DDL, then reset it.
Move DDL timestamp helper functions into pkg/sink/mysql/helper.go for reuse and keep mysql_writer_ddl.go focused.
Add unit tests to cover the conditional session timestamp behavior.

Check List

Tests

Unit test

Manual test

-- create changefeed
CREATE DATABASE IF NOT EXISTS test_time_funcs;
USE test_time_funcs;
-- Timestamp & Datetime Functions
-- Test: NOW(), CURRENT_TIMESTAMP(), CURRENT_TIMESTAMP, LOCALTIME(), LOCALTIME, LOCALTIMESTAMP, LOCALTIMESTAMP(), UTC_TIMESTAMP()
CREATE TABLE t_timestamp (id INT PRIMARY KEY, info VARCHAR(20));
INSERT INTO t_timestamp VALUES (1, 'initial_row');
-- pause the changefeed
ALTER TABLE t_timestamp ADD COLUMN ts_now DATETIME DEFAULT NOW();
ALTER TABLE t_timestamp ADD COLUMN ts_current_timestamp_func TIMESTAMP DEFAULT CURRENT_TIMESTAMP();
ALTER TABLE t_timestamp ADD COLUMN ts_current_timestamp_const TIMESTAMP DEFAULT CURRENT_TIMESTAMP;
ALTER TABLE t_timestamp ADD COLUMN ts_localtime_func TIMESTAMP DEFAULT LOCALTIME();
ALTER TABLE t_timestamp ADD COLUMN ts_localtime_const TIMESTAMP DEFAULT LOCALTIME;
ALTER TABLE t_timestamp ADD COLUMN ts_localtimestamp_func TIMESTAMP DEFAULT LOCALTIMESTAMP();
ALTER TABLE t_timestamp ADD COLUMN ts_localtimestamp_const TIMESTAMP DEFAULT LOCALTIMESTAMP;
SELECT * FROM test_time_funcs.t_timestamp\G
-- wait for seconds & resume the changefeed
SELECT * FROM test_time_funcs.t_timestamp\G

Questions

Will it cause performance regression or break compatibility?

No. The change only affects DDL execution for CURRENT_TIMESTAMP-style defaults and does not alter DML paths.

Do you need to update user documentation, design documentation or monitoring documentation?

No.

Release note

Fix MySQL sink DDL execution to apply CURRENT_TIMESTAMP-style defaults using upstream origin_default values for consistent initial data.

- Add StartTs field to DDLEvent struct for preserving upstream execution timestamps - Update MySQL sink to set session timestamps based on upstream StartTs/CommitTs - Add proper session timestamp management with fallback logic - Enhance error handling for timestamp-related failures - Fix timestamp drift issues for DDL statements with NOW(), CURRENT_TIMESTAMP(), etc.

When executing DDLs, check for in the table info and use it to set the session . This ensures columns with are initialized with the exact same time as the upstream.

…ault_current_timestamp

pingcap-cla-assistant · 2026-01-13T03:29:24Z

All committers have signed the CLA.

gemini-code-assist · 2026-01-13T03:29:27Z

Summary of Changes

Hello @haiboumich, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the MySQL sink's DDL execution mechanism to maintain data consistency when dealing with columns that have CURRENT_TIMESTAMP-style default values. By programmatically aligning the session timestamp with the original upstream DDL execution time for such columns, it prevents discrepancies in initial data values that could arise from different application times or timezones, ensuring that the replicated schema accurately reflects the source.

Highlights

Problem Solved: Addresses data inconsistency for DDLs adding columns with CURRENT_TIMESTAMP-style defaults by ensuring the downstream system uses the upstream-evaluated default value.
DDL Execution Alignment: Implements logic to parse DDL statements, detect columns with CURRENT_TIMESTAMP, NOW, LOCALTIME, or LOCALTIMESTAMP defaults, and temporarily set the MySQL session @@timestamp to the column's origin_default value before execution.
Code Refactoring: Moves DDL timestamp-related helper functions into pkg/sink/mysql/helper.go to improve modularity and keep mysql_writer_ddl.go focused.
Testing: Adds comprehensive unit tests to validate the conditional session timestamp behavior during DDL execution.

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Code Review

This pull request introduces a mechanism to align CURRENT_TIMESTAMP-style default values in DDLs with the upstream values by setting the session @@timestamp. The logic is well-encapsulated in pkg/sink/mysql/helper.go, and new unit tests are added to verify the behavior. The changes are well-structured and improve data consistency. My review identified a few minor logging issues where the wrong error variable was being used in error logs, which could hinder debugging.

gemini-code-assist · 2026-01-13T03:30:56Z

pkg/sink/mysql/mysql_writer_ddl.go

+				zap.String("query", event.GetDDLQuery()),
+				zap.Error(err))
+			if rbErr := tx.Rollback(); rbErr != nil {
+				log.Error("Failed to rollback", zap.Error(err))


The wrong error variable err is used here for logging. It should be rbErr to log the actual rollback error.

Suggested change

log.Error("Failed to rollback", zap.Error(err))

log.Error("Failed to rollback", zap.Error(rbErr))

gemini-code-assist · 2026-01-13T03:30:56Z

pkg/sink/mysql/mysql_writer_ddl.go

+			}
+		}
 		if rbErr := tx.Rollback(); rbErr != nil {
 			log.Error("Failed to rollback", zap.String("sql", event.GetDDLQuery()), zap.Error(err))


The wrong error variable err is used here for logging. It should be rbErr to log the actual rollback error.

Suggested change

log.Error("Failed to rollback", zap.String("sql", event.GetDDLQuery()), zap.Error(err))

log.Error("Failed to rollback", zap.String("sql", event.GetDDLQuery()), zap.Error(rbErr))

gemini-code-assist · 2026-01-13T03:30:57Z

pkg/sink/mysql/mysql_writer_ddl.go

+		if err := resetSessionTimestamp(ctx, tx); err != nil {
+			log.Error("Failed to reset session timestamp after DDL execution", zap.Error(err))
+			if rbErr := tx.Rollback(); rbErr != nil {
+				log.Error("Failed to rollback", zap.String("sql", event.GetDDLQuery()), zap.Error(err))


The wrong error variable err is used here for logging. It should be rbErr to log the actual rollback error.

Suggested change

log.Error("Failed to rollback", zap.String("sql", event.GetDDLQuery()), zap.Error(err))

log.Error("Failed to rollback", zap.String("sql", event.GetDDLQuery()), zap.Error(rbErr))

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ti-chi-bot · 2026-01-14T11:07:37Z

[APPROVALNOTIFIER] This PR is NOT APPROVED

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haiboumich · 2026-01-15T06:54:35Z

/retest-required

haiboumich · 2026-01-15T07:59:33Z

/run-check-issue-triage-complete

haiboumich · 2026-01-15T08:02:14Z

/retest-required

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wk989898 · 2026-01-16T07:45:36Z

Please add unit tests and integration tests 🙏🏻

haiboumich and others added 9 commits December 5, 2025 00:54

sink/mysql: use OriginDefaultValue for DDL session timestamp

fb2cfcb

When executing DDLs, check for in the table info and use it to set the session . This ensures columns with are initialized with the exact same time as the upstream.

update

7da1b77

add ut

a41e5fc

Merge branch 'pingcap:master' into shenhaibo/fix-handle-alter-add-def…

8444977

…ault_current_timestamp

ddl: use origin_default for session timestamp

8cf60b4

ddl: update order

4afdab9

sink/mysql: move DDL timestamp helpers to helper.go

109da5d

test: drop rollback expectation in async DDL test

0c5b11f

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ti-chi-bot bot added the size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. label Jan 13, 2026

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haiboumich added 3 commits January 13, 2026 14:45

ticdc: refine code

dc51b74

ticdc: update log:

c1d8963

ticdc: update log

c5c2b30

Debra-He approved these changes Jan 14, 2026

View reviewed changes

zier-one approved these changes Jan 14, 2026

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ti-chi-bot bot added do-not-merge/needs-triage-completed and removed do-not-merge/needs-linked-issue labels Jan 15, 2026

ti-chi-bot bot removed the do-not-merge/needs-triage-completed label Jan 15, 2026

	log.Error("Failed to rollback", zap.Error(err))
	log.Error("Failed to rollback", zap.Error(rbErr))

	log.Error("Failed to rollback", zap.String("sql", event.GetDDLQuery()), zap.Error(err))
	log.Error("Failed to rollback", zap.String("sql", event.GetDDLQuery()), zap.Error(rbErr))

sink/mysql: align DDL time defaults with origin_default #3991

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sink/mysql: align DDL time defaults with origin_default #3991

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