Re: Using multiple extended statistics for estimates

From: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
To: Mark Dilger <hornschnorter(at)gmail(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Using multiple extended statistics for estimates
Date: 2019-12-09 22:00:17
Message-ID: 20191209220017.6eidna5ai7z2wdf5@development
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On Mon, Dec 09, 2019 at 11:56:39AM -0800, Mark Dilger wrote:
>On 12/5/19 9:51 AM, Tomas Vondra wrote:
>>On Thu, Dec 05, 2019 at 06:15:54PM +0100, Tomas Vondra wrote:
>>>On Sun, Dec 01, 2019 at 08:08:58PM +0100, Tomas Vondra wrote:
>>>>On Sat, Nov 30, 2019 at 03:01:31PM -0800, Mark Dilger wrote:
>>>>>Are you planning to submit a revised patch for this?
>>>>Yes, I'll submit a rebased version of this patch shortly. I got broken
>>>>because of the recent fix in choose_best_statistics, shouldn't take long
>>>>to update the patch. I do have a couple more related patches in the
>>>>queue, so I want to submit them all at once.
>>>OK, here we go - these two patched allow applying multiple extended
>>>statistics, both for MCV and functional dependencies. Functional
>>>dependencies are simply merged and then applied at once (so withouth
>>>choose_best_statistics), statistics are considered in greedy manner by
>>>calling choose_best_statistics in a loop.
>>OK, this time with the patches actually attached ;-)
>These look good to me. I added extra tests (not included in this email)
>to verify the code on more interesting test cases, such as partitioned
>tables and within joins. Your test cases are pretty trivial, just being
>selects from a single table.

Adding such more complex tests seem like a good idea, maybe you'd like
to share them?

>I'll go mark this "ready for committer".

Thanks for the review. I'll hold-off with the commit until the next CF,
though, just to give others a proper opportunity to look at it.


Tomas Vondra
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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