Re: BUG #1756: PQexec eats huge amounts of memory - Mailing list pgsql-bugs

From Tom Lane
Subject Re: BUG #1756: PQexec eats huge amounts of memory
Date
Msg-id 1809.1121265821@sss.pgh.pa.us
Whole thread Raw
In response to Re: BUG #1756: PQexec eats huge amounts of memory  (Denis Vlasenko <vda@ilport.com.ua>)
Responses Re: BUG #1756: PQexec eats huge amounts of memory
List pgsql-bugs
Denis Vlasenko <vda@ilport.com.ua> writes:
> Consider my posts in this thread as user wish to
> * libpq and network protocol to be changed to allow for incremental reads
>   of executed queries and for multiple outstanding result sets,
>     or, if above thing looks unsurmountable at the moment,
> * libpq-only change as to allow incremental reads of single outstanding
>   result set. Attempt to use pg_numrows, etc, or attempt to execute
>   another query forces libpq to read and store all remaining rows
>   in client's memory (i.e. current behaviour).

This isn't going to happen because it would be a fundamental change in
libpq's behavior and would undoubtedly break a lot of applications.
The reason it cannot be done transparently is that you would lose the
guarantee that a query either succeeds or fails: it would be entirely
possible to return some rows to the application and only later get a
failure.

You can have this behavior today, though, as long as you are willing to
work a little harder at it --- just declare some cursors and then FETCH
in convenient chunks from the cursors.

            regards, tom lane

pgsql-bugs by date:

Previous
From: Tom Lane
Date:
Subject: Re: BUG #1764: newbie
Next
From: "ISHIDA Akio"
Date:
Subject: BUG #1766: contrib/ modules can't install with --without-docdir