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Handle lack of DSM slots in parallel btree build.

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If no DSM slots are available, a ParallelContext can still be
created, but its seg pointer is NULL.  Teach parallel btree build
to cope with that by falling back to a regular non-parallel build,
to avoid crashing with a segmentation fault.

Back-patch to 11, where parallel CREATE INDEX landed.

Reported-by: Nicola Contu
Reviewed-by: Peter Geoghegan
Discussion: https://postgr.es/m/CA%2BhUKGJgJEBnkuODBVomyK3MWFvDBbMVj%3Dgdt6DnRPU-5sQ6UQ%40mail.gmail.com
This commit is contained in:
Thomas Munro 2020-01-31 10:25:34 +13:00
parent a5b652f3a0
commit 2c56b3ac43
1 changed files with 9 additions and 0 deletions
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9
src/backend/access/nbtree/nbtsort.c
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@ -1256,6 +1256,15 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request)
Assert(request > 0); Assert(request > 0);
pcxt = CreateParallelContext("postgres", "_bt_parallel_build_main", pcxt = CreateParallelContext("postgres", "_bt_parallel_build_main",
request, true); request, true);
/* If no DSM segment was available, back out (do serial build) */
if (pcxt->seg == NULL)
{
DestroyParallelContext(pcxt);
ExitParallelMode();
return;
}
scantuplesortstates = leaderparticipates ? request + 1 : request; scantuplesortstates = leaderparticipates ? request + 1 : request;
/* /*