[pgpool-committers: 6636] pgpool: Fix bug with query cache.

[Tatsuo Ishii]

Fix bug with query cache.

If an execute message is issued right after Sync message and query
cache hits, Pgpool-II hangs in inject_cached_message() because there's
no data to be read from backend. Fix is, change the code block which
checks the data availability in backend to the beginning of the loop
from the end of the loop. Also teach is_cache_empty() to call
pool_is_suspend_reading_from_frontend() so that if we suspend reading
from frontend. If so, return that cache is empty even if there's data
in frontend cache to receive a ready for query message from backend.

Branch
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V3_7_STABLE

Details
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https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=9c5dcd20a3e11d8fc6780e961ffb59c60ed60fd9

Modified Files
--------------
src/protocol/pool_process_query.c | 23 +++++++++++++----------
src/query_cache/pool_memqcache.c  | 30 +++++++++++++++---------------
2 files changed, 28 insertions(+), 25 deletions(-)