From: Terry Lee Tucker <terry@esc1.com>
To: PostgreSQL Interfaces <pgsql-interfaces@postgresql.org>
Subject: Re: libpq, blocking/nonblocking mechanism
Date: Wed, 1 Jun 2005 15:10:10 -0400
Message-ID: <200506011510.10371.terry@esc1.com> (raw)
In-Reply-To: <7104a7370506011118270bf58f@mail.gmail.com>
References: <7104a737050528133410045f04@mail.gmail.com>
<200505310651.54505.terry@esc1.com>
<7104a7370506011118270bf58f@mail.gmail.com>
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.
From 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
and it returns immediately if you have set nonblocking to true. If you have
not set nonblocking to true, then PQsendQuery behaves just like PQexec; it
blocks, i.e., it waits for the query, update, delete, or whatever to complete
before it returns program control back to your program. We set nonblocking to
True in our application and when the user queries a large table that could
return thousands of records, we use PQsendQuery instead of PQexec; however,
if you do that, then you have to use PQconsumeInput and PQisBusy in
conjunction with a select statement to monitor the backend connection socket
so you can process the results when the query finishes. Another reason for
using asynchronous queries is that you can provide a mechanism for the user
to cancel the operation. Our application is X-Windows based written in C.
All my examples are C. If you want to see any of it, you can let me know.
>
> Regards.
>
> ---------------------------(end of broadcast)---------------------------
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To: pgsql-interfaces@postgresql.org
Cc: terry@esc1.com
Subject: Re: libpq, blocking/nonblocking mechanism
In-Reply-To: <200506011510.10371.terry@esc1.com>
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