BUG#34930969: Previous_gtids miss gtid when binlog_order_commits off

Problem

When binlog_order_commits is turned off, binlog rotate will wait for m_prep_xids to decrease to zero. However, m_prep_xids was decreased before updating the thread GTID to gtid_executed in MYSQL_BIN_LOG::finish_commit, causing GTIDs to be missed in the next binlog file Previous_gtids event.

Fix

The core fix moves dec_prep_xids to be called after gtid_state->update_on_commit in MYSQL_BIN_LOG::finish_commit. This ensures that when binlog rotate waits for m_prep_xids to reach zero, all GTIDs have already been registered in gtid_executed.

Additionally:

• Added DEBUG_SYNC point after_dec_prep_xids to enable deterministic testing
• Added MTR test case rpl_previous_gtids to verify the fix

Commit

https://github.com/xyw0537/TXSQL/commit/ae7de225c2a

Branch: bugfix/previous_gtids_miss_gtid_binlog_order_commits_off

Upstream Reference

https://github.com/mysql/mysql-server/commit/a3faa6f8799e6c7c610245d2899386131731fb41

首先定位 MYSQL_BIN_LOG::finish_commit，并检查 dec_prep_xids 和 gtid_state->update_on_commit 的顺序。检查 after_dec_prep_xids DEBUG_SYNC 点和 MTR 测试用例 rpl_previous_gtids。完成的标准是测试验证在 binlog_order_commits 关闭时，Previous_gtids 包含所有已提交的 GTID。