Re: How to share the result data of separated plan
Tom Lane <tgl@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Marko Tiikkaja <marko.tiikkaja@cs.helsinki.fi>
Cc: Robert Haas <robertmhaas@gmail.com>,
Hitoshi Harada <umi.tanuki@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2010-11-08T18:30:58Z
Lists: pgsql-hackers
Marko Tiikkaja <marko.tiikkaja@cs.helsinki.fi> writes: > On 2010-11-08 7:26 PM +0200, Tom Lane wrote: >> The alternative is to artificially serialize the DML CTEs, which >> while it does have some advantages doesn't seem like a win overall. > We've discussed this before and the consensus was that as long as we > don't change the results, we can optimize the materialization away. No, because the problem is mainly about what might happen if user-defined functions choose to look at the target tables. We can't really tell what triggers are going to do, to take one item that the planner has no access to. I think we have to decide up front which implementation behavior it's going to be, and if we go with serialized queries, we'll be stuck with that. regards, tom lane