[pgpool-committers: 5398] pgpool: Fix occasional extended query hang.

[Tatsuo Ishii]

Fix occasional extended query hang.

If a client sends a extended query message such as close after sync
message but before next simple query, Pgpool-II could hang.

:
<= BE ParseComplete
<= BE BindComplete
<= BE CommandComplete(COMMIT)
<= BE ReadyForQuery(I)
FE=> Close(stmt="S2")
FE=> Close(stmt="S1")
FE=> Query (query="BEGIN") [0]
<= BE CloseComplete [1]
<= BE CloseComplete [1]
<= BE CommandComplete(BEGIN) [2]

Because of [1], query in progress flag was reset, then [2] hangs
trying to read from backend which did not receive message from
Pgpool-II because it does not refer to the query context set by [0].

Sending close after sync is not recommended according to the official
document but some sloppy drivers seem to do it. To deal with the
problem, check the doing extended query message flag before resetting
the query in progress flag.

Problem reported by Muhammad Usama.
Discussion: https://www.pgpool.net/pipermail/pgpool-hackers/2018-December/003164.html

Branch
------
V3_6_STABLE

Details
-------
https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=733852e6ab8b9e9acb0c6972660f5379392860f5

Modified Files
--------------
src/protocol/pool_proto_modules.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)