pg.ddx.io pgsql-hackers@postgresql.org mailing list archive help / color / mirror / Atom feed From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Rowley <david.rowley@2ndquadrant.com>
Cc: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
Cc: Dmitry Dolgov <9erthalion6@gmail.com>
Cc: Jeff Janes <jeff.janes@gmail.com>
Cc: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>
Cc: Pavel Stehule <pavel.stehule@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: why partition pruning doesn't work?
Date: Mon, 11 Jun 2018 10:26:32 -0400
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David Rowley <david.rowley@2ndquadrant.com> writes:
> On 11 June 2018 at 10:49, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> * The business with ExecFindInitialMatchingSubPlans remapping the
>> subplan indexes seems very dubious to me. Surely, that is adding
>> way more complexity and fragility than it's worth.
> I think having the ability to prune during executor initialisation is
> enormously important. I think without it, this patch is less than half
> as useful.
Sure.
> However, if you didn't mean removing the executor
> initialise pruning, and just not remapping the arrays, then I'm not
> sure how we'd do that. I'd previously tried having NULL subnodes in
> the Append and I thought it required too much hacking work in
> explain.c, so I decided to just collapse the array instead and do what
> was required to make it work after having removed the unneeded
> subplans. Did you have another idea on how to do this?
No, that was pretty much exactly what I was envisioning. I have
not looked at the consequences for explain.c but it seemed like
it couldn't be all that bad; and to my mind the remapping business
in the partition code is pretty bad. "It's all in one file" is not
a suitable justification for unintelligible, overcomplex code.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, david.rowley@2ndquadrant.com, Langote_Amit_f8@lab.ntt.co.jp, 9erthalion6@gmail.com, jeff.janes@gmail.com, ashutosh.bapat@enterprisedb.com, pavel.stehule@gmail.com, pgsql-hackers@lists.postgresql.org
Subject: Re: why partition pruning doesn't work?
In-Reply-To: <556.1528727192@sss.pgh.pa.us>
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