From: Terry Lee Tucker <terry@esc1.com>
Organization: Enhanced Solutions Computing
To: PostgreSQL Interfaces <pgsql-interfaces@postgresql.org>
Subject: Re: libpq, blocking/nonblocking mechanism
Date: Wed, 1 Jun 2005 15:10:10 -0400
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On Wednesday 01 June 2005 02:18 pm, Volkan YAZICI saith:
> Hi,
>
> On 5/31/05, Terry Lee Tucker <terry@esc1.com> wrote:
> [snipped]
>
> > I'm looking at the documentation in:
> > file:/usr/share/doc/postgresql-7.4.6/html/libpq-async.html
> > on my machine.
>
> Thanks so much, but I'm able to read manuals too.

=46rom your original message:
"P.S. Documentation pointers will be accepted with pleasure too."

> I'm trying to don't
> carry my questions here until I finish a satisfying
> postgresql.org/docs plus google.com search. Namely, I read that lines
> nearly I hundred times.
>
> I advice you to looking at my question twice.
PQsetnonblocking () causes PQsendQuery to send an sql string to the backend=
=20
and it returns immediately if you have set nonblocking to true. If you have=
=20
not set nonblocking to true, then PQsendQuery behaves just like PQexec; it=
=20
blocks, i.e., it waits for the query, update, delete, or whatever to comple=
te=20
before it returns program control back to your program. We set nonblocking =
to=20
True in our application and when the user queries a large table that could=
=20
return thousands of records, we use PQsendQuery instead of PQexec; however,=
=20
if you do that, then you have to use PQconsumeInput and PQisBusy in=20
conjunction with a select statement to monitor the backend connection socke=
t=20
so you can process the results when the query finishes. Another reason for=
=20
using asynchronous queries is that you can provide a mechanism for the user=
=20
to cancel the operation.  Our application is X-Windows based written in C.=
=20
All my examples are C. If you want to see any of it, you can let me know.

>
> Regards.
>
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