Re: Poor performance on seq scan - Mailing list pgsql-performance

From Markus Schaber
Subject Re: Poor performance on seq scan
Date
Msg-id 450E5728.7000802@logix-tt.com
Whole thread Raw
In response to Re: Poor performance on seq scan  (Piotr Kołaczkowski <P.Kolaczkowski@elka.pw.edu.pl>)
List pgsql-performance
Hi, Piotr,

Piotr Kołaczkowski wrote:

> Why match rows from the heap if ALL required data are in the index itself?
> Why look at the heap at all?

Because the index does not contain any transaction informations, so it
has to look to the heap to find out which of the rows are current.

This is one of the more debated points in the PostgreSQL way of MVCC
implementation.


Markus


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Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

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