| From: | Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: How to share the result data of separated plan |
| Date: | 2010-11-08 22:38:15 |
| Message-ID: | 4CD87BD7.6040009@cs.helsinki.fi |
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| Lists: | pgsql-hackers |
On 2010-11-08 8:30 PM +0200, Tom Lane wrote:
> Marko Tiikkaja<marko(dot)tiikkaja(at)cs(dot)helsinki(dot)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.
The relevant thread seems to be this one:
http://archives.postgresql.org/pgsql-hackers/2009-11/msg00003.php
and I do agree with what you said there.
Regards,
Marko Tiikkaja
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