[pgpool-committers: 6857] 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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V3_6_STABLE

Details
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https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=24fb5d6e728efeedc8ade771fd13b8f914af32e7

Modified Files
--------------
src/include/query_cache/pool_memqcache.h        |   3 +-
src/protocol/pool_proto_modules.c               |   7 +-
src/query_cache/pool_memqcache.c                | 136 +++++++++++++++++++++++-
src/test/regression/tests/006.memqcache/test.sh |   6 ++
src/utils/pool_select_walker.c                  |   6 ++
5 files changed, 151 insertions(+), 7 deletions(-)