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Re: WIP patch for parameterized inner paths

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: WIP patch for parameterized inner paths
Date: 2012-01-26 19:48:54
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Lists: pgsql-hackers
On Thu, Jan 26, 2012 at 2:27 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>>>> Is there a guard in here against joining a parameterized path to an
>>>> intermediate relation when no SJ is involved?  In other words, if
>>>> we're joining a parameterized path on A to a path on B, then either
>>>> the join to B should satisfy at least part of the parameterization
>>>> needed by A, or there should be a special join with A and B on one
>>>> side and a relation that satisfies at least part of the
>>>> parameterization of A on the other.
> I've implemented this idea, recast a bit to prevent generating a
> parameterized join path in the first place unless it depends on a
> parameter from a relation for which there's a join ordering constraint
> still outstanding.  It seems to get us to where the planning time
> penalty is only about 10%, which frankly is probably less than sampling
> error considering the small set of test cases I'm looking at.

Awesome.  If you can post the updated patch, I'll poke at it a little
more and see if anything jumps out at me, but that sounds promising.

Robert Haas
The Enterprise PostgreSQL Company

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