pgsql: Refactor PredicateLockShmemInit to not reuse var for different t

Refactor PredicateLockShmemInit to not reuse var for different things

The PredicateLockShmemInit function is pretty complicated, and one
source of confusion is that it reuses the same local variable for
sizes of things. Replace the different uses with separate variables
for clarity.

Reviewed-by: Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>
Discussion: https://www.postgresql.org/message-id/113724ab-0028-493f-9605-6e8570f0939f@iki.fi

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3fd0577728277e66f072f3b07adf78299dfad7cc

Modified Files
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src/backend/storage/lmgr/predicate.c | 68 +++++++++++++++++++-----------------
1 file changed, 35 insertions(+), 33 deletions(-)