Re: slight tweaks to documentation about runtime pruning

Alvaro Herrera <alvherre@2ndquadrant.com>

From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: David Rowley <david.rowley@2ndquadrant.com>
Cc: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2018-12-16T22:30:10Z
Lists: pgsql-hackers
On 2018-Dec-10, David Rowley wrote:

> On Wed, 5 Dec 2018 at 20:24, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> wrote:

> > However, for pruned partitions' subplans, what's actually shown is the
> > string "(never executed)", not loops.  So, wouldn't it be better to tell
> > the readers to look for that instead of "loops"?
> 
> I don't really see any issues with the existing documentation here.
> Remember that pruning can be performed multiple times when a parameter
> changes that was found to match the partition key and the
> Append/MergeAppend is rescanned.

I lean towards Amit's side.  I think we're too laconic about many
details of EXPLAIN's output.  This is two lines about an interesting
detail that's pretty obscure.  It doesn't hurt to have it there.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


Commits

  1. Clarify runtime pruning in EXPLAIN