Re: ANTI-JOIN needs table, index scan not possible?

From: Maciek Sakrejda <msakrejda(at)truviso(dot)com>
To: hans wulf <lotu1(at)gmx(dot)net>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: ANTI-JOIN needs table, index scan not possible?
Date: 2011-03-11 17:18:19
Message-ID: AANLkTink26wyiPdjdd=Tv-me=XFempCnjsJDGj0wbrhJ@mail.gmail.com
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> I know the table has to be visitied at some point to serve the MVCC, but why so early? Can NOT ESISTS only be fixed by the table, because it could miss soemthing otherwise?

Possibly because the index entries you're anti-joining against may
point to deleted tuples, so you would erroneously omit rows from the
join result if you skip the visibility check?

---
Maciek Sakrejda | System Architect | Truviso

1065 E. Hillsdale Blvd., Suite 215
Foster City, CA 94404
(650) 242-3500 Main
www.truviso.com

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