Date: Thu, 4 Jan 2018 16:20:23 -0300
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
	Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>,
	Jesper Pedersen <jesper.pedersen@redhat.com>,
	David Rowley <david.rowley@2ndquadrant.com>,
	Simon Riggs <simon@2ndquadrant.com>,
	Pg Hackers <pgsql-hackers@postgresql.org>,
	Maksim Milyutin <milyutinma@gmail.com>
Subject: Re: [HACKERS] Proposal: Local indexes for partitioned table
Message-ID: <20180104192023.pylv7jveepit2245@alvherre.pgsql>
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Robert Haas wrote:
> On Thu, Jan 4, 2018 at 11:44 AM, Peter Eisentraut
> <peter.eisentraut@2ndquadrant.com> wrote:
> > I'm not sure why this feature of automatically picking up matching
> > indexes even exists.  Is it for some specific workflows or upgrade
> > scenarios?  It's kind of a surprising feature in a way.
> 
> It allows you to avoid building a new indexes unnecessarily when
> attaching a partition.

Yeah -- this is important to reduce the duration of the DDL operation,
since attaching a partition requires an access exclusive lock.  Having
to build the index at that point would make that feature pretty much
useless for many use cases.

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