pgsql: Get rid of duplicate child RTE for a partitioned table.

Get rid of duplicate child RTE for a partitioned table.

We've been creating duplicate RTEs for partitioned tables just
because we do so for regular inheritance parent tables. But unlike
regular-inheritance parents which are themselves regular tables
and thus need to be scanned, partitioned tables don't need the
extra RTE.

This makes the conditions for building a child RTE the same as those
for building an AppendRelInfo, allowing minor simplification in
expand_single_inheritance_child. Since the planner's actual processing
is driven off the AppendRelInfo list, nothing much changes beyond that,
we just have one fewer useless RTE entry.

Amit Langote, reviewed and hacked a bit by me

Discussion: https://postgr.es/m/9d7c5112-cb99-6a47-d3be-cf1ee6862a1d@lab.ntt.co.jp

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/e8d5dd6be79ed532710922105c31a2d25b14430f

Modified Files
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contrib/postgres_fdw/expected/postgres_fdw.out | 2 +-
src/backend/optimizer/util/inherit.c | 86 +++++++++++++-------------
2 files changed, 45 insertions(+), 43 deletions(-)