pgsql: Fix NULL handling in multi-batch Parallel Hash Left Join.

Fix NULL handling in multi-batch Parallel Hash Left Join.

NULL keys in left joins were skipped when building batch files.
Repair, by making the keep_nulls argument to ExecHashGetHashValue()
depend on whether this is a left outer join, as we do in other
paths.

Bug #15475.  Thinko in 1804284042e.  Back-patch to 11.

Reported-by: Paul Schaap
Diagnosed-by: Andrew Gierth
Dicussion: https://postgr.es/m/15475-11a7a783fed72a36%40postgresql.org

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/fd6449aa38759cc35c32c1d5bf87c516ba6385c8

Modified Files
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src/backend/executor/nodeHashjoin.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)