Horton

Re: Automatic free space map filling

Csaba Nagy <nagy@ecircle-ag.com>

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From: Csaba Nagy <nagy@ecircle-ag.com>
To: Bruce Momjian <pgman@candle.pha.pa.us>
Cc: Alvaro Herrera <alvherre@commandprompt.com>, "Matthew T. O'Connor" <matthew@zeut.net>, Christopher Browne <cbbrowne@acm.org>, postgres hackers <pgsql-hackers@postgresql.org>
Date: 2006-03-03T15:14:41Z
Lists: pgsql-hackers 
> Ewe.  How expensive is scanning an index compared to the heap?  Does
> anyone have figure on that in terms of I/O and time?

See this post for an example:
http://archives.postgresql.org/pgsql-performance/2006-02/msg00416.php

For my 200 million table, scanning the pk index took ~ 4 hours. And then
there are some more indexes...

So if the index has to be scanned completely, that's still too much.

Cheers,
Csaba.