pgsql: Speed up "brin" regression test a little bit.

Speed up "brin" regression test a little bit.

In the large DO block, collect row TIDs into array variables instead of
creating and dropping a pile of temporary tables. In a normal build,
this reduces the brin test script's runtime from about 1.1 sec to 0.4 sec
on my workstation. That's not all that exciting perhaps, but in a
CLOBBER_CACHE_ALWAYS test build, the runtime drops from 20 min to 17 min,
which is a little more useful. In combination with some other changes
I plan to propose, this will help provide a noticeable reduction in
cycle time for CLOBBER_CACHE_ALWAYS buildfarm critters.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/242066cc8e587ccbe5e1cf38c4f085f080dcd5e0

Modified Files
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src/test/regress/expected/brin.out | 42 ++++++++++++++------------------------
src/test/regress/sql/brin.sql | 42 ++++++++++++++------------------------
2 files changed, 30 insertions(+), 54 deletions(-)