Horton

Re: [HACKERS] advanced partition matching algorithm for partition-wise join

Tomas Vondra <tomas.vondra@2ndquadrant.com>

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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Cc: Etsuro Fujita <etsuro.fujita@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Kuntal Ghosh <kuntalghosh.2007@gmail.com>, Ashutosh Bapat <ashutosh.bapat@2ndquadrant.com>, Mark Dilger <mark.dilger@enterprisedb.com>, amul sul <sulamul@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, Rajkumar Raghuwanshi <rajkumar.raghuwanshi@enterprisedb.com>, Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>, Dmitry Dolgov <9erthalion6@gmail.com>, Antonin Houska <ah@cybertec.at>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2020-04-09T14:41:00Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Suppress unused-variable warning.

  2. Allow partitionwise joins in more cases.

  3. Avoid crash in partitionwise join planning under GEQO.

  4. Disable support for partitionwise joins in problematic cases.

  5. Add plan_cache_mode setting

  6. Add test for partitionwise join involving default partition.

  7. Revise API for partition_rbound_cmp/partition_rbound_datum_cmp.

On Thu, Apr 09, 2020 at 07:34:01PM +0530, Ashutosh Bapat wrote:
>On Thu, Apr 9, 2020 at 12:03 PM Etsuro Fujita <etsuro.fujita@gmail.com> wrote:
>>
>> On Thu, Apr 9, 2020 at 2:36 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> > Etsuro Fujita <etsuro.fujita@gmail.com> writes:
>> > > Yeah, partition_bounds_merge() is currently called only from
>> > > try_partitionwise_join(), which guarantees that the strategies are the
>> > > same.
>>
>> > If there's only one caller and there's not likely to ever be more,
>> > then I tend to agree that you don't need the assertion.
>>
>> It seems unlikely that partition_bounds_merge() will be called from
>> more places in the foreseeable future, so I'd still vote for removing
>> the assertion.
>
>When I wrote that function, I had UNION also in mind. A UNION across
>multiple partitioned relations will be partitioned if we can merge the
>partition bounds in a sensible manner. Of course the current structure
>of that function looks more purposed for join, but it's not difficult
>to convert it to be used for UNION as well. In that case those set of
>functions will have many more callers. So, I will vote to keep that
>assertion now that we have it there.

Yeah. I really don't see why we should remove an assertion that enforces
something useful, especially when it's just a plain comparions. Had it
been some expensive assert, maybe. But how much slower does this make
an assert-enabled build? 0.000000000001% or something like that?


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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