From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Mon, 18 Oct 2021 17:42:10 +0000 (+0300)
Subject: Fix parallel sort, broken by the balanced merge patch.
X-Git-Tag: REL_15_BETA1~1339
X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=fc0f3b4cb0e882a9c5d51c302d4aa3591e4f80fd;p=postgresql.git

Fix parallel sort, broken by the balanced merge patch.

The code for initializing the tapes on each merge iteration was skipped
in a parallel worker. I put the !WORKER(state) check in wrong place while
rebasing the patch.

That caused failures in the index build in 'multiple-row-versions'
isolation test, in multiple buildfarm members. On my laptop it was easier
to reproduce by building an index on a larger table, so that you got a
parallel sort more reliably.
---

diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index 0c5c574cbd3..9e93908c657 100644
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -2923,7 +2923,7 @@ mergeruns(Tuplesortstate *state)
 		 * Rewind all the output tapes, and make them inputs for the next
 		 * pass.
 		 */
-		if (state->nInputRuns == 0 && !WORKER(state))
+		if (state->nInputRuns == 0)
 		{
 			int64		input_buffer_size;
 
@@ -2975,7 +2975,8 @@ mergeruns(Tuplesortstate *state)
 			 * sorted tape, we can stop at this point and do the final merge
 			 * on-the-fly.
 			 */
-			if (!state->randomAccess && state->nInputRuns <= state->nInputTapes)
+			if (!state->randomAccess && state->nInputRuns <= state->nInputTapes
+				&& !WORKER(state))
 			{
 				/* Tell logtape.c we won't be writing anymore */
 				LogicalTapeSetForgetFreeSpace(state->tapeset);