Re: WIP: Upper planner pathification

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: WIP: Upper planner pathification
Date: 2016-03-09 17:19:21
Message-ID: CA+TgmoaV+63k26eV3Du861mFBw3=PzPmju=auCHQ231x8x4KgA@mail.gmail.com
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On Wed, Mar 9, 2016 at 12:07 PM, Alvaro Herrera
<alvherre(at)2ndquadrant(dot)com> wrote:
> Tom Lane wrote:
>> Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> writes:
>
>> > Without setting max_parallel_degree, it works fine and generate the
>> > appropriate results. Here the issue seems to be that the code in
>> > grouping_planner doesn't apply the required PathTarget to Path below Gather
>> > Path due to which when we generate target list for scan plan,
>>
>> Yeah, fixed. I had assumed that the existing coding in create_gather_plan
>> was OK, because it looked like it was right for a non-projecting node.
>> But actually Gather can project (why though?), so it's not right.
>
> This looks related:
> https://www.postgresql.org/message-id/CA%2BTgmoai9Ruhwk61110rY4cNAzoO6npsFEOaEKjM7Zz8i3evHg%40mail.gmail.com

I actually wrote a patch for this:

http://www.postgresql.org/message-id/CA+TgmoaqWH8W35c7pssuufxOO=AxNEQEN4da_BkeQaA3SE33QQ@mail.gmail.com

I assume it no longer applies :-( but I think it would be good to get
this into 9.6. It's a pretty simple optimization with a lot to
recommend it.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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