[pgpool-committers: 8708] pgpool: Fix bug in query cache.

[Tatsuo Ishii]

Fix bug in query cache.

[pgpool-general: 8285] Timestamp cast not cached

reported that query like "Select '2022-02-18
07:00:00.006547’::timestamp" is not cached.

The function non_immutable_function_call_walker() which judges whether
the query contains non immutable functions mistakenly assumes that any
query including cast to timestamp etc. should not to be cached. These
codes were originally added to detect CURRENT_TIMESTAMP etc. as they
are transformed to type cast in raw parser. Unfortunately this is
overkill since "'2022-02-18 07:00:00.006547’::timestamp" is also
transformed to a type cast.

Fortunately Pgpool-II 3.7 and after imported PostgreSQL 10 or newer
parser, which transforms CURRENT_TIMESTAMP etc. to SQLValueFunction.

As a result, the type cast handling code in
non_immutable_function_call_walker() is not necessary anymore. So this
commit removed the code.

Note: an interested thing in the report is, "Select '2022-02-18
07:00:00.006547’::timestamp" is not cached while "Select '2022-02-18
07:00:00.006547’::date" is cached. Why? Well
non_immutable_function_call_walker() (wrongly) assumes that the type
cache is always created by SystemTypeName (a parser's function), which
always adds pg_catalog schema. This only happens when the type name is
a reserved keyword. TIMESTAMP is a reserved keyword (and TIME too). So
non_immutable_function_call_walker() catches TIMESTAMP cast as
expected, but DATE is not a reserved keyword and it is transformed to
type name without "pg_catalog" schema. So
non_immutable_function_call_walker() misses it, and it is cached.

Branch
------
master

Details
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https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=266eee00c6df0a208c8f68623f645735e6ef5f9f

Modified Files
--------------
src/utils/pool_select_walker.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)