Re: libpq ASYNC with PQgetResult and PQisBusy

Raimon Fernandez <coder(at)montx(dot)com> writes:
> Almost everything is working, and now I want to implememt the asynchronous issue.

> I send the SQL using the PQsendQuery, and my interface is not blocking, great.

> Now, everytime I check fot the PQgetResult my interface gets blocked.

Well, yes. PQgetResult says wait for a result and return it.

> So, now I'm using the PQisBusy to check if postgre is still busy and I can safely call the PQgetResult wihtout blocking, or just wait *some time* before sending a new PQisBusy.

Your proposed code is still a busy-wait loop. What you should be doing
is waiting for some data to arrive on the socket. Once you see
read-ready on the socket, call PQconsumeInput, then check PQisBusy to
see if the query is complete or not. If not, go back to waiting on the
socket. Typically you'd use select() or poll() to watch for both data
on libpq's socket and whatever other events your app is interested in.

> here is my montxPG_isBusy

> static long montxPG_isBusy()

> { int execStatus;
> int consumeeVar;

> consumeeVar = PQconsumeInput(gPGconn);

> if (consumeeVar == 0) return (long) PGRES_FATAL_ERROR;

> execStatus = PQisBusy(gPGconn);

> return (long) execStatus;

> }

This code seems a bit confused. PQisBusy returns a bool (1/0), not a
value of ExecStatusType.

regards, tom lane