Re: Surfacing qualifiers

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Fetter <david@fetter.org>
Cc: Andrew Dunstan <andrew@dunslane.net>, PG Hackers <pgsql-hackers@postgresql.org>
Date: 2008-03-26T17:21:14Z
Lists: pgsql-hackers
David Fetter <david@fetter.org> writes:
> What happens now with dblink is that the remote table (more generally,
> the output of a fixed query) gets materialized into memory in its
> entirety, and if it's bigger than what's available, it will crash the
> backend or worse.

This is utter nonsense.  It gets put into a tuplestore which is entirely
capable of spilling to disk.  Slow, yes, but crashing is a lie.

> That happens because functions do not have any
> access to the predicates with which they were called, so the current
> workaround is to pass the predicates manually and then cast.

dblink is not a suitable framework for improving that situation.
Maybe someday we'll have a proper implementation of SQL/MED ...

			regards, tom lane