Re: Removing [Merge]Append nodes which contain a single subpath

From: Antonin Houska <ah(at)cybertec(dot)at>
To: David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Removing [Merge]Append nodes which contain a single subpath
Date: 2017-10-26 10:42:51
Message-ID: 12435.1509014571@localhost
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David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> wrote:

> Method 1:
>
> In set_append_rel_size() detect when just a single subpath would be
> added to the Append path.

I spent some time reviewing the partition-wise join patch during the last CF
and have an impression that set_append_rel_size() is called too early to find
out how many child paths will eventually exist if Append represents a join of
a partitioned table. I think the partition matching takes place at later stage
and that determines the actual number of partitions, and therefore the number
of Append subpaths.

--
Antonin Houska
Cybertec Schönig & Schönig GmbH
Gröhrmühlgasse 26
A-2700 Wiener Neustadt
Web: http://www.postgresql-support.de, http://www.cybertec.at

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