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For inplace update, send nontransactional invalidations.

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The inplace update survives ROLLBACK.  The inval didn't, so another
backend's DDL could then update the row without incorporating the
inplace update.  In the test this fixes, a mix of CREATE INDEX and ALTER
TABLE resulted in a table with an index, yet relhasindex=f.  That is a
source of index corruption.  Back-patch to v12 (all supported versions).
The back branch versions don't change WAL, because those branches just
added end-of-recovery SIResetAll().  All branches change the ABI of
extern function PrepareToInvalidateCacheTuple().  No PGXN extension
calls that, and there's no apparent use case in extensions.

Reviewed by Nitin Motiani and (in earlier versions) Andres Freund.

Discussion: https://postgr.es/m/20240523000548.58.nmisch@google.com
This commit is contained in:
Noah Misch
2024-10-25 06:51:02 -07:00
parent 67f30c79a1
commit 0ea9d40a66
11 changed files with 290 additions and 118 deletions
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26
src/backend/access/transam/xact.c
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@ -1249,14 +1249,24 @@ RecordTransactionCommit(void)
/*
* Transactions without an assigned xid can contain invalidation
* messages (e.g. explicit relcache invalidations or catcache
* invalidations for inplace updates); standbys need to process those.
* We can't emit a commit record without an xid, and we don't want to
* force assigning an xid, because that'd be problematic for e.g.
* vacuum. Hence we emit a bespoke record for the invalidations. We
* don't want to use that in case a commit record is emitted, so they
* happen synchronously with commits (besides not wanting to emit more
* WAL records).
* messages. While inplace updates do this, this is not known to be
* necessary; see comment at inplace CacheInvalidateHeapTuple().
* Extensions might still rely on this capability, and standbys may
* need to process those invals. We can't emit a commit record
* without an xid, and we don't want to force assigning an xid,
* because that'd be problematic for e.g. vacuum. Hence we emit a
* bespoke record for the invalidations. We don't want to use that in
* case a commit record is emitted, so they happen synchronously with
* commits (besides not wanting to emit more WAL records).
*
* XXX Every known use of this capability is a defect. Since an XID
* isn't controlling visibility of the change that prompted invals,
* other sessions need the inval even if this transactions aborts.
*
* ON COMMIT DELETE ROWS does a nontransactional index_build(), which
* queues a relcache inval, including in transactions without an xid
* that had read the (empty) table. Standbys don't need any ON COMMIT
* DELETE ROWS invals, but we've not done the work to withhold them.
*/
if (nmsgs != 0)
{