postgres.git / summary / log / commit / refs

commit    f83040c62a78e784e6e33a6382a55925bfd66634
Author:   Andres Freund <andres@anarazel.de>
Date:     Thu Dec 28 10:41:53 2017 +0000
First released in: 11.0

    Fix rare assertion failure in parallel hash join.
    
    When a backend runs out of inner tuples to hash, it should detach from
    grow_batch_barrier only after it has flushed all batches to disk and
    merged counters, not before.  Otherwise a concurrent backend in
    ExecParallelHashIncreaseNumBatches() could stop waiting for this
    backend and try to read tuples before they have been written.  This
    commit reorders those operations and should fix the assertion failures
    seen occasionally on the build farm since commit
    1804284042e659e7d16904e7bbb0ad546394b6a3.
    
    Author: Thomas Munro
    Discussion: https://postgr.es/m/E1eRwXy-0004IK-TO%40gemulon.postgresql.org


 src/backend/executor/nodeHash.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/backend/executor/nodeHash.c b/src/backend/executor/nodeHash.c
index 0a519fae313..04eb3650aa3 100644
--- a/src/backend/executor/nodeHash.c
+++ b/src/backend/executor/nodeHash.c
@@ -288,8 +288,6 @@ MultiExecParallelHash(HashState *node)
 					ExecParallelHashTableInsert(hashtable, slot, hashvalue);
 				hashtable->partialTuples++;
 			}
-			BarrierDetach(&pstate->grow_buckets_barrier);
-			BarrierDetach(&pstate->grow_batches_barrier);
 
 			/*
 			 * Make sure that any tuples we wrote to disk are visible to
@@ -304,6 +302,9 @@ MultiExecParallelHash(HashState *node)
 			 */
 			ExecParallelHashMergeCounters(hashtable);
 
+			BarrierDetach(&pstate->grow_buckets_barrier);
+			BarrierDetach(&pstate->grow_batches_barrier);
+
 			/*
 			 * Wait for everyone to finish building and flushing files and
 			 * counters.


[parent: be2343221fb7]