[pgpool-committers: 8591] pgpool: Fix not to abort session while in failed transaction.

[Tatsuo Ishii]

Fix not to abort session while in failed transaction.

When an explicit transaction fails, subsequent commands should be
ignored until commit or rollback command comes in. However pgpool
sometimes aborted the session if relcache lookup happened. example:

test=# begin;
BEGIN
test=*# insert into ttt values(1);
ERROR:  relation "ttt" does not exist
LINE 1: insert into ttt values(1);
                    ^
test=!# select * from t1;
FATAL:  Backend throw an error message
DETAIL:  Exiting current session because of an error from backend
HINT:  BACKEND Error: "current transaction is aborted, commands ignored until end of transaction block"
server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
The connection to the server was lost. Attempting reset: Succeeded.

To prevent  this, check the transaction  state and if it's  already in
aborted state, do not try to  process the command, but just reply back
to frontend with an error message:

ERROR:  current transaction is aborted, commands ignored until end of transaction block

By the way, while implementing the fix, I found old bugs with replication mode.

- ReadyForQuery() mistakenly called end_internal_transaction() even if
  it's not in replication/si mode. Moreover,
  end_internal_transaction() is called even if the internal
  transaction has not started.

- end_internal_transaction() did not call pool_unset_failed_transaction();

These bugs were harmless until I tried to fix the issue (session
aborting).

New regression test 078 for this added.

Discussion: https://www.pgpool.net/pipermail/pgpool-general/2022-April/008155.html

Branch
------
V4_3_STABLE

Details
-------
https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=22320057bb1c2e3ab13fcb9c9ac585b145f98109

Modified Files
--------------
src/protocol/pool_process_query.c                  |  1 +
src/protocol/pool_proto_modules.c                  | 70 +++++++++++++++++++++-
.../tests/078.aborted_transaction/expected.txt     | 28 +++++++++
.../tests/078.aborted_transaction/test.sh          | 48 +++++++++++++++
4 files changed, 144 insertions(+), 3 deletions(-)