Re: speeding up planning with partitions

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>
Cc: Imai Yoshikazu <yoshikazu_i443(at)live(dot)jp>, "jesper(dot)pedersen(at)redhat(dot)com" <jesper(dot)pedersen(at)redhat(dot)com>, "Imai, Yoshikazu" <imai(dot)yoshikazu(at)jp(dot)fujitsu(dot)com>, "'Amit Langote'" <amitlangote09(at)gmail(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: speeding up planning with partitions
Date: 2019-03-26 22:26:31
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Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> writes:
> On 2019/03/23 6:07, Tom Lane wrote:
>> I also feel like you used a dartboard while deciding where to insert the
>> call in query_planner(); dropping it into the middle of a sequence of
>> equivalence-class-related operations seems quite random. Maybe we could
>> delay that step all the way to just before make_one_rel, since the other
>> stuff in between seems to only care about baserels? For example,
>> it'd certainly be better if we could run remove_useless_joins before
>> otherrel expansion, so that we needn't do otherrel expansion at all
>> on a table that gets thrown away as being a useless join.

> create_lateral_join_info() expects otherrels to be present to propagate
> the information it creates.

Sure, but the actually-useful work in that function is just concerned
with baserels. The only thing it does with otherrels is to propagate
parents' lateral-ref info to children, which is a lot easier, cheaper,
and more reliable if we let build_simple_rel do it. See the version
of 0001 I just pushed.

I'll look at 0003 and up tomorrow.

regards, tom lane

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