pgsql: A small tweak to some comments for PartitionKeyData

A small tweak to some comments for PartitionKeyData

It was not really that obvious that there's meant to be exactly 1 item
in the partexprs List for each zero-valued partattrs element.  Some
incorrect code using these fields was the cause of CVE-2018-1052, so
it's worthwhile to mention how they should be used in the comments.

Author: David Rowley <david.rowley@2ndquadrant.com>

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/7ac0069fb880b9b64223f104058c82773321851c

Modified Files
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src/include/utils/partcache.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)