message missing in handle_response

Sorry, I was wrong.

If you found it within the make check, the cause is not here.

In make check, test script sometimes cancels statement execution
intentionally. This cancellation is done in asynchronous manner and
when the cancellation takes time, typically in slower environment,
following script has to run while the cancellation is not complete.

Unfortunately, it is not simple to perform this cancellation in
synchronous manner. Instead, we inserted some wait before the next
script is ready to run. We understand this is not complete and we
still have a good chance to have such error occasionally.

You can ignore this. If you write an application where you cancel
statement execution intentionally, then you should be careful to see
if the cancellation is complete.

Thank you very much for pointing out.

Please also understand the limitation I mentioned is collect.

Regards;

Koichi Suzuki

2014-09-26 11:29 GMT+09:00 peace zone peacezone@users.sf.net:

Thanks for your response!
1. I found this condition during doing the make check.
2. Do we have a plan to adding this feature?

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[bugs:#490] message missing in handle_response

Status: open
Group: 1.2 Dev Q
Created: Mon Sep 22, 2014 09:41 AM UTC by peace zone
Last Updated: Mon Sep 22, 2014 09:41 AM UTC
Owner: nobody

I execute a user define function and get two different results. Both the two
results appear randomly, the result2 is expected.

Results
results1:
postgres=# select trap_foreign_key(2);
NOTICE: caught foreign_key_violation
ERROR: failed to send COMMIT command to node

results2:
postgres=# select trap_foreign_key(2);
NOTICE: caught foreign_key_violation
trap_foreign_key

---

0
(1 row)

Object definition
CREATE TABLE master(f1 int primary key);
CREATE TABLE slave(f1 int references master deferrable);

CREATE FUNCTION trap_foreign_key(int) RETURNS INT AS $$
BEGIN
begin -- start transaction
insert into slave values($1);
exception
when foreign_key_violation then
raise notice 'caught foreign_key_violation';
return 0;
end;
return 1;
end$$ language plpgsql;

select trap_foreign_key(2); – detects FK violation

Debug output

I add a elog in handle_reponse() of coordinator:

msg_type = get_message(conn, &msg_len, &msg);
elog(WARNING, "Received message type: %c", msg_type);

The debug output is in the attachment.
As the debug output shows, the result1 misses the N, Z messages from
datanode.

Reason

The reason is when the coordinator in justifing message buffer,
the datanode has not yet send the messages.The coordinator thinks
there is no message now, and return, the later messages from datanode is
missed.

The coordinator code:
if (!HAS_MESSAGE_BUFFERED(conn))
return RESPONSE_EOF;

The N,Z messages comes later than the check above.

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