postgres.git / summary / log / commit / refs

commit    74618e77b43cfce670b4725d5b9a300a2afd12d1
Author:   Thomas Munro <tmunro@postgresql.org>
Date:     Thu Jan 30 21:25:34 2020 +0000
First released in: 13.0, 11.7, 12.2

    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 f163491d600..e6be7bba594 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;
 
 	/*


[parent: c9d297751959]