pgsql: Allow left join removals and unique joins on partitioned tables

Allow left join removals and unique joins on partitioned tables

This allows left join removals and unique joins to work with partitioned
tables.  The planner just lacked sufficient proofs that a given join
would not cause any row duplication.  Unique indexes currently serve as
that proof, so have get_relation_info() populate the indexlist for
partitioned tables too.

Author: Arne Roland
Reviewed-by: Alvaro Herrera, Zhihong Yu, Amit Langote, David Rowley
Discussion: https://postgr.es/m/c3b2408b7a39433b8230bbcd02e9f302@index.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3c569049b7b502bb4952483d19ce622ff0af5fd6

Modified Files
--------------
src/backend/optimizer/util/plancat.c         | 264 +++++++++++++++------------
src/backend/utils/adt/selfuncs.c             |   4 +
src/include/nodes/pathnodes.h                |  10 +-
src/test/regress/expected/join.out           |  10 +
src/test/regress/expected/partition_join.out |   4 +-
src/test/regress/sql/join.sql                |   7 +
src/test/regress/sql/partition_join.sql      |   4 +-
7 files changed, 179 insertions(+), 124 deletions(-)