[pgpool-committers: 8649] pgpool: Fix internal transaction handling bug in snapshot isolation mod

[Tatsuo Ishii]

Fix internal transaction handling bug in snapshot isolation mode.

When SELECT is executed in snapshot isolation mode, it is surrounded
in an "internal transaction".  For example if there are 3 backends,
each backend starts an internal transaction with "BEGIN" command.
However, there was an oversight in end_internal_transaction(), which
is responsible for closing the transaction. It only closed the
transaction on "load balance node". This causes a problem with certain
query following SELECT, for example VACUUM. Suppose the SELECT is
executed on backend node 2, then transaction on node 0 and node 1 were
not closed. If VACUUM is executed on node 0, it fails because the
transaction is not closed on node 0 (remember, VACUUM cannot be
executed in an explicit transaction).

Also add a test case for this to the 030.snapshot_isolation test.

Branch
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V4_2_STABLE

Details
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https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=102517e30022162b111633510f849a49d1c53e0f

Modified Files
--------------
src/protocol/pool_process_query.c                  | 45 +++++++++++++++++++---
.../tests/030.snapshot_isolation/expected.txt      |  6 +++
.../tests/030.snapshot_isolation/test.sh           | 14 +++++++
3 files changed, 59 insertions(+), 6 deletions(-)