From: | Raimon Fernandez <coder(at)montx(dot)com> |
---|---|
To: | pgsql-general List <pgsql-general(at)postgresql(dot)org> |
Subject: | libpq ASYNC with PQgetResult and PQisBusy |
Date: | 2010-12-20 13:19:41 |
Message-ID: | 2F4AE0A3-673D-4CC4-8D35-D04FAB10F5FC@montx.com |
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Lists: | pgsql-general |
Hello,
I'm trying to create a plugin using the libpq.
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.
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.
Before every PQisBusy i call PQconsumeInput to update the status.
So, in pseudo code:
1. PQsendQuery (a really slow select just to check the asyncronous)
2. From a timer every 0.2 seconds, I call:
2.1 PQconsumeInput
2.2 PQisBusy
2.3 evaluate => if it's busy => sleep and start again from 2 ; if it's not busy, continue
2.4 call PQgetResult
Using PQisBusy it's not working, it's taking really longer to just send the 0 (non-busy) and at this moment the PQgetResult is null.
If I force to call the PQgetResult after just one second of the PQsendQuery I can get the PQgetResult, without testing the PQisBusy.
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;
}
thanks,
regards,
r.
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