From 74618e77b43cfce670b4725d5b9a300a2afd12d1 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Fri, 31 Jan 2020 10:25:34 +1300 Subject: [PATCH] Handle lack of DSM slots in parallel btree build. 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 --- src/backend/access/nbtree/nbtsort.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/src/backend/access/nbtree/nbtsort.c b/src/backend/access/nbtree/nbtsort.c index f163491d60..e6be7bba59 100644 --- a/src/backend/access/nbtree/nbtsort.c +++ b/src/backend/access/nbtree/nbtsort.c @@ -1331,6 +1331,15 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request) Assert(request > 0); pcxt = CreateParallelContext("postgres", "_bt_parallel_build_main", request); + + /* If no DSM segment was available, back out (do serial build) */ + if (pcxt->seg == NULL) + { + DestroyParallelContext(pcxt); + ExitParallelMode(); + return; + } + scantuplesortstates = leaderparticipates ? request + 1 : request; /*