Subject: Re: [COMMITTERS] pgsql: If we expect a hash join to be performed
	in multiple batches,
From: Simon Riggs <simon@2ndQuadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@postgresql.org
In-Reply-To: <20202.1238701799@sss.pgh.pa.us>
References: <20090326171535.6B9BF754ADE@cvs.postgresql.org>
	<1238692283.5444.123.camel@ebony.2ndQuadrant>
	<20202.1238701799@sss.pgh.pa.us>
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Date: Thu, 02 Apr 2009 21:32:56 +0100
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On Thu, 2009-04-02 at 15:49 -0400, Tom Lane wrote:
> Simon Riggs <simon@2ndquadrant.com> writes:
> > Can we add "batches=N" to the EXPLAIN output for Hash and/or Hash Join?
> 
> Are you talking about expected batches, or actual batches?  

Expected batches for EXPLAIN, both for EXPLAIN ANALYZE.

> If the
> former, would it be sufficient to distinguish "1" from "more than 1"?
> If so, maybe changing the node title to "Batched Hash" would do.

Hmmm, knowing the number of batches is beneficial since it helps you to
calculate the required memory to get best performance.

-- 
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support