pgsql: Fix two problems in infer_arbiter_indexes().

Fix two problems in infer_arbiter_indexes().

The first is a pretty simple bug where a relcache entry is used after
the relation is closed. In this particular situation it does not appear
to have bad consequences unless compiled with RELCACHE_FORCE_RELEASE.

The second is that infer_arbiter_indexes() skipped indexes that aren't
yet valid according to indcheckxmin. That's not required here, because
uniqueness checks don't care about visibility according to an older
snapshot. While thats not really a bug, it makes things undesirably
non-deterministic. There is some hope that this explains a test failure
on buildfarm member jaguarundi.

Discussion: 9096(dot)1431102730(at)sss(dot)pgh(dot)pa(dot)us

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/bab64ef9e8bc56fa5db9bd41cefb54c3d8051dbe

Modified Files
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src/backend/optimizer/util/plancat.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)