pgsql: In the executor,use an array of pointers to access the rangetab

In the executor, use an array of pointers to access the rangetable.

Instead of doing a lot of list_nth() accesses to es_range_table,
create a flattened pointer array during executor startup and index
into that to get at individual RangeTblEntrys.

This eliminates one source of O(N^2) behavior with lots of partitions.
(I'm not exactly convinced that it's the most important source, but
it's an easy one to fix.)

Amit Langote and David Rowley

Discussion: https://postgr.es/m/468c85d9-540e-66a2-1dde-fec2b741e688@lab.ntt.co.jp

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d73f4c74dd34b19c19839f7ae09fb96442728509

Modified Files
--------------
contrib/postgres_fdw/postgres_fdw.c      | 12 ++++----
src/backend/commands/copy.c              |  5 ++--
src/backend/commands/trigger.c           |  2 +-
src/backend/executor/execExprInterp.c    |  6 ++--
src/backend/executor/execMain.c          | 34 +++++++++-------------
src/backend/executor/execUtils.c         | 49 +++++++++++++++++++++++++++++---
src/backend/executor/nodeLockRows.c      |  2 +-
src/backend/replication/logical/worker.c |  3 +-
src/include/executor/executor.h          |  9 ++++++
src/include/nodes/execnodes.h            |  7 +++--
src/include/parser/parsetree.h           | 10 -------
11 files changed, 87 insertions(+), 52 deletions(-)