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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Thomas Munro <thomas.munro@gmail.com>
Cc: Melanie Plageman <melanieplageman@gmail.com>
Cc: hackers <pgsql-hackers@postgresql.org>
Subject: Re: accounting for memory used for BufFile during hash joins
Date: Mon, 06 May 2019 23:18:28 -0400
Message-ID: <27902.1557199108@sss.pgh.pa.us> (raw)
In-Reply-To: <20190507031511.lvp6bqn2e5dpsnga@development>
References: <20190504003414.bulcbnge3rhwhcsh@development>
	<CAAKRu_ZTy=a2jqj0++jDwke1_ssJTBB0ezU2t8OwogmXDbYdYw@mail.gmail.com>
	<CA+hUKG+ppih9DtZwGJh4KMZXdtD=c9+fYoS1CSeBQBs9JzZtbA@mail.gmail.com>
	<20190507031511.lvp6bqn2e5dpsnga@development>

Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
> Do we actually check how many duplicates are there during planning?

Certainly that's part of the planner's cost estimates ... but it's
only as good as the planner's statistical knowledge.

			regards, tom lane

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