[COMMITTERS] pgsql: Don't lock tables in RelationGetPartitionDispatchInfo.

Don't lock tables in RelationGetPartitionDispatchInfo.

Instead, lock them in the caller using find_all_inheritors so that
they get locked in the standard order, minimizing deadlock risks.

Also in RelationGetPartitionDispatchInfo, avoid opening tables which
are not partitioned; there's no need.

Amit Langote, reviewed by Ashutosh Bapat and Amit Khandekar

Discussion: http://postgr.es/m/91b36fa1-c197-b72f-ca6e-56c593bae68c@lab.ntt.co.jp

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/54cde0c4c05807321d3f4bf96a97c376e3fa91cb

Modified Files
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src/backend/catalog/partition.c | 55 ++++++++++++++++++++++-------------------
src/backend/executor/execMain.c | 10 +++++---
src/include/catalog/partition.h |  3 +--
3 files changed, 37 insertions(+), 31 deletions(-)