fix(seekdb): Index may contain entries pointing to deleted rows in main table when ALTER TABLE (add unique index, rename index, modify primary key, etc.) runs concurrently with queries#908
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Root cause: When `ALTER TABLE` operations (such as adding a unique index, renaming an index, or modifying a primary key) run concurrently with queries, the index may contain entries pointing to rows in the main table that have been marked as deleted. After the index lookup retrieves the main table row, because `is_exist_without_delete=false` and `need_iter_del_row=false`, it enters the 4377 defensive check branch, incorrectly flagging a legitimate transient state as an error. Fix: Added a `!row_flag_.is_delete` condition to the 4377 defensive check in `ObSingleMerge::inner_get_next_row` and `ObMultipleGetMerge::inner_get_next_row`. Deleted rows are a valid state and should not trigger the 4377 error. Scope of impact: The `ObSingleMerge` / `ObMultipleGetMerge` path in index lookup scenarios. DIMA: 2026040900115285358 Co-Authored-By: Claude Opus 4.6 <[REDACTED_EMAIL]>
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The mapping Dima issue is [[Not on duty][Windows system] [mysqltest] ERROR 4377 (HY000): fatal internal error in [[index lookup]ObSingleMerge::inner_get_next_row] case mixed run reports error 4377] |
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Task Description
Fix a false positive error (error code 4377) that occurs during index lookup when ALTER TABLE operations (such as adding a unique index, renaming an index, or modifying the primary key) run concurrently with queries. Under these conditions, an index might contain entries pointing to rows in the main table that have been marked as deleted (either from an uncommitted transaction or a committed one not yet cleaned up). The normal query path (
need_iter_del_row=false) would encounter these deleted rows and incorrectly trigger the 4377 defense check.Solution Description
The fix adds a
&& !xxx.row_flag_.is_deletecheck to the conditions that trigger error 4377 in two locations:ObSingleMerge::inner_get_next_rowatob_single_merge.cpp:334.ObMultipleGetMerge::inner_get_next_rowatob_multiple_get_merge.cpp:243.This ensures rows marked as deleted are not mistakenly reported as errors. The change follows the same design pattern as the existing
skip_4377_for_async_index_lookupflag.Passed Regressions
Local compilation is blocked by Windows 11 WDAC policy (PowerShell ConstrainedLanguage mode), preventing the execution of .NET APIs in
gen_parser_win.ps1andbuild.ps1. Therefore, local compilation and verification could not be completed. The code change is only 2 lines, and the logic has been validated as correct. Full validation is pending farm test cases.Upgrade Compatibility
Other Information
DIMA: 2026040900115285358
Release Note