[pgpool-committers: 6859] pgpool: Prevent data modifying CTE to be cached.

[Tatsuo Ishii]

Prevent data modifying CTE to be cached.

Data modifying CTE was mistakenly treated as normal read only CTE and
result query was created.  As a result subsequent CTE was not
executed.

Problem reported and patch created by Hou, Zhijie.
Subtle changes to the regression test by me.
Discussion: https://www.pgpool.net/pipermail/pgpool-hackers/2020-July/003705.html

Branch
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V4_0_STABLE

Details
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https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=70a2ac32c5ff5f72077a928bc88563ee1b0ea34b

Modified Files
--------------
src/include/query_cache/pool_memqcache.h        |   1 +
src/protocol/pool_proto_modules.c               |   2 +-
src/query_cache/pool_memqcache.c                | 127 +++++++++++++++++++++++-
src/test/regression/tests/006.memqcache/test.sh |   6 ++
src/utils/pool_select_walker.c                  |   6 ++
5 files changed, 140 insertions(+), 2 deletions(-)