[pgpool-committers: 5396] 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_7_STABLE

Details
-------
https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=5625f06c1915a5bc7fffa6eeecc9913385a697c2

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