pgsql: Fix oversized memory allocation in Parallel Hash Join

Fix oversized memory allocation in Parallel Hash Join

During the calculations of the maximum for the number of buckets, take into
account that later we round that to the next power of 2.

Reported-by: Karen Talarico
Bug: #16925
Discussion: https://postgr.es/m/16925-ec96d83529d0d629%40postgresql.org
Author: Thomas Munro, Andrei Lepikhov, Alexander Korotkov
Reviewed-by: Alena Rybakina
Backpatch-through: 12

Branch
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REL_14_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/3bdaa8fc622f51ab2836314a9f087b6af81eef06

Modified Files
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src/backend/executor/nodeHash.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)