Thread: pgsql: Avoid GatherMerge crash when there are no workers.

Avoid GatherMerge crash when there are no workers.

It's unnecessary to return an actual slot when we have no tuple.
We can just return NULL, which avoids the risk of indexing into an
array that might not contain any elements.

Rushabh Lathia, per a report from Tomas Vondra

Discussion: http://postgr.es/m/6ecd6f17-0dcf-1de7-ded8-0de7db1ddc88@2ndquadrant.com

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/25dc142a49c60c3107480c487cd8444dc83f9bdf

Modified Files
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src/backend/executor/nodeGatherMerge.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)