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Commit43e409c

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Backpatch nbtree page deletion hardening.
Postgres 14 commit5b861ba taught nbtree VACUUM to tolerate buggyopclasses. VACUUM's inability to locate a to-be-deleted page's downlinkin the parent page was logged instead of throwing an error. VACUUMcould just press on with vacuuming the index, and vacuuming the table asa whole.There are now anecdotal reports of this error causing problems that weremuch more disruptive than the underlying index corruption ever could be.Anything that makes VACUUM unable to make forward progress against onetable/index ultimately risks making the system enter xidStopLimit mode.There is no good reason to take any chances here, so backpatch thehardening commit.Author: Peter Geoghegan <pg@bowt.ie>Discussion:https://postgr.es/m/CAH2-Wzm9HR6Pow=t-iQa57zT8qmX6_M4h14F-pTtb=xFDW5FBA@mail.gmail.comBackpatch: 10-13 (all supported versions that lacked the hardening)
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‎src/backend/access/nbtree/nbtpage.c

Lines changed: 17 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2388,10 +2388,26 @@ _bt_lock_subtree_parent(Relation rel, BlockNumber child, BTStack stack,
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*/
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pbuf=_bt_getstackbuf(rel,stack,child);
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if (pbuf==InvalidBuffer)
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ereport(ERROR,
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{
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/*
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* Failed to "re-find" a pivot tuple whose downlink matched our child
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* block number on the parent level -- the index must be corrupt.
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* Don't even try to delete the leafbuf subtree. Just report the
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* issue and press on with vacuuming the index.
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*
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* Note: _bt_getstackbuf() recovers from concurrent page splits that
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* take place on the parent level. Its approach is a near-exhaustive
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* linear search. This also gives it a surprisingly good chance of
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* recovering in the event of a buggy or inconsistent opclass. But we
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* don't rely on that here.
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*/
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ereport(LOG,
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(errcode(ERRCODE_INDEX_CORRUPTED),
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errmsg_internal("failed to re-find parent key in index \"%s\" for deletion target page %u",
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RelationGetRelationName(rel),child)));
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return false;
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}
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parent=stack->bts_blkno;
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parentoffset=stack->bts_offset;
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