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