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Tom Lane 92c49d1062 Fix insertion of SP-GiST REDIRECT tuples during REINDEX CONCURRENTLY. ... Reconstruction of an SP-GiST index by REINDEX CONCURRENTLY may insert some REDIRECT tuples. This will typically happen in a transaction that lacks an XID, which leads either to assertion failure in spgFormDeadTuple or to insertion of a REDIRECT tuple with zero xid. The latter's not good either, since eventually VACUUM will apply GlobalVisTestIsRemovableXid() to the zero xid, resulting in either an assertion failure or a garbage answer. In practice, since REINDEX CONCURRENTLY locks out index scans till it's done, it doesn't matter whether it inserts REDIRECTs or PLACEHOLDERs; and likewise it doesn't matter how soon VACUUM reduces such a REDIRECT to a PLACEHOLDER. So in non-assert builds there's no observable problem here, other than perhaps a little index bloat. But it's not behaving as intended. To fix, remove the failing Assert in spgFormDeadTuple, acknowledging that we might sometimes insert a zero XID; and guard VACUUM's GlobalVisTestIsRemovableXid() call with a test for valid XID, ensuring that we'll reduce such a REDIRECT the first time VACUUM sees it. (Versions before v14 use TransactionIdPrecedes here, which won't fail on zero xid, so they really have no bug at all in non-assert builds.) Another solution could be to not create REDIRECTs at all during REINDEX CONCURRENTLY, making the relevant code paths treat that case like index build (which likewise knows that no concurrent index scans can be happening). That would allow restoring the Assert in spgFormDeadTuple, but we'd still need the VACUUM change because redirection tuples with zero xid may be out there already. But there doesn't seem to be a nice way for spginsert() to tell that it's being called in REINDEX CONCURRENTLY without some API changes, so we'll leave that as a possible future improvement. In HEAD, also rename the SpGistState.myXid field to redirectXid, which seems less misleading (since it might not in fact be our transaction's XID) and is certainly less uninformatively generic. Per bug #18499 from Alexander Lakhin. Back-patch to all supported branches. Discussion: https://postgr.es/m/18499-8a519c280f956480@postgresql.org		2 years ago
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backend	Fix insertion of SP-GiST REDIRECT tuples during REINDEX CONCURRENTLY.	2 years ago
bin	pg_createsubscriber: Remove failover replication slots on subscriber	2 years ago
common	jsonapi: Some message style fixes	2 years ago
fe_utils	Fix PL/pgSQL's handling of integer ranges containing underscores.	2 years ago
include	Fix insertion of SP-GiST REDIRECT tuples during REINDEX CONCURRENTLY.	2 years ago
interfaces	Improve the granularity of PQsocketPoll's timeout parameter.	2 years ago
makefiles	…
pl	When replanning a plpgsql "simple expression", check it's still simple.	2 years ago
port	Pre-beta mechanical code beautification.	2 years ago
template	…
test	Improve tracking of role dependencies of pg_init_privs entries.	2 years ago
timezone	…
tools	Improve the granularity of PQsocketPoll's timeout parameter.	2 years ago
tutorial	…
.gitignore	…
DEVELOPERS	…
Makefile	…
Makefile.global.in	…
Makefile.shlib	…
meson.build	…
nls-global.mk	…