Re: [HACKERS] Runtime Partition Pruning

From: David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>
To: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Cc: Amit Langote <amitlangote09(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>, Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, Beena Emerson <memissemerson(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, amul sul <sulamul(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>
Subject: Re: [HACKERS] Runtime Partition Pruning
Date: 2018-04-07 12:33:37
Message-ID: CAKJS1f9CfuGi1FLwj054taExXfd7sfXc+BwR0avPjYQv9hNWSA@mail.gmail.com
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On 8 April 2018 at 00:23, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> I edited it as attached, to 1. avoid mentioning functionality that
> doesn't yet exist, and 2. avoid excessive internal detail (we want a
> high-level overview here), which from experience gets outdated pretty
> quickly.

It's not exactly wrong but:

+ * are turned into a set of "pruning steps", which are then executed to
+ * produce a set of RTIs of partitions whose bounds satisfy the constraints in
+ * the step. Partitions not in the set are said to have been pruned.

It's only prune_append_rel_partitions which is only used for the
planner's pruning needs that converts the partition indexes to RTIs.
Would it be better to mention that the output is partition indexes?
Maybe:

"which are then executed to produce a set of partition indexes whose
bounds satisfy the constraints in the step. These partition indexes
may then be translated into RTIs", or maybe even not mention the RTIs.

--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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