Re: cursor interface to libpq limited by virtual memory

Below is a post from 2000. It describes a limitation processing large
selects with libpq. Does this limitation still exist?

Thanks in advance,
Bob Gilson

Kirby Bohling wrote:
>>I am trying to run a select statement, and I keep running out of
>>memory. After a little investigate, I found
>>that libpq appears to get the entire result set at once.

The bottleneck here is mainly that libpq's API is defined in terms of
providing random access to a result set, no matter how large --- so
libpq has to buffer the whole result set in client memory.

Aside from random access there are also error-reporting issues.
Currently libpq guarantees to tell you about any errors encountered
during a query before you start to read result rows. That guarantee
wouldn't hold in a streaming-results scenario.

These issues have been discussed quite a few times before --- see the
pg-interfaces archives. I think everyone agrees that it'd be a good
idea to have a streamable libpq interface, but no one's stepped up to
the plate to define or implement one...

regards, tom lane