pgsql: Assorted preparatory refactoring for partition-wise join.

Assorted preparatory refactoring for partition-wise join.

Instead of duplicating the logic to search for a matching
ParamPathInfo in multiple places, factor it out into a separate
function.

Pass only the relevant bits of the PartitionKey to
partition_bounds_equal instead of the whole thing, because
partition-wise join will want to call this without having a
PartitionKey available.

Adjust allow_star_schema_join and calc_nestloop_required_outer
to take relevant Relids rather than the entire Path, because
partition-wise join will want to call it with the top-parent
relids to determine whether a child join is allowable.

Ashutosh Bapat. Review and testing of the larger patch set of which
this is a part by Amit Langote, Rajkumar Raghuwanshi, Rafia Sabih,
Thomas Munro, Dilip Kumar, and me.

Discussion: http://postgr.es/m/CA+TgmobQK80vtXjAsPZWWXd7c8u13G86gmuLupN+uUJjA+i4nA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/e139f1953f29db245f60a7acb72fccb1e05d2442

Modified Files
--------------
src/backend/catalog/partition.c | 9 ++++---
src/backend/optimizer/path/joinpath.c | 27 +++++++++++----------
src/backend/optimizer/util/pathnode.c | 11 +++++----
src/backend/optimizer/util/relnode.c | 45 ++++++++++++++++++++---------------
src/backend/utils/cache/relcache.c | 4 +++-
src/include/catalog/partition.h | 5 ++--
src/include/optimizer/pathnode.h | 7 +++++-
7 files changed, 62 insertions(+), 46 deletions(-)