pgsql: Optimize roles_is_member_of() with a Bloom filter.

Optimize roles_is_member_of() with a Bloom filter.

When the list of roles gathered by roles_is_member_of() grows very
large, a Bloom filter is created to help avoid some linear searches
through the list.  The threshold for creating the Bloom filter is
set arbitrarily high and may require future adjustment.

Suggested-by: Tom Lane
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/CAGvXd3OSMbJQwOSc-Tq-Ro1CAz%3DvggErdSG7pv2s6vmmTOLJSg%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d365ae705409f5d9c81da4b668f59c3598feb512

Modified Files
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src/backend/utils/adt/acl.c | 68 +++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 65 insertions(+), 3 deletions(-)