Re: Bitmap Heap scan 8.1/8.2 - Mailing list pgsql-general

From Martin Marques
Subject Re: Bitmap Heap scan 8.1/8.2
Date
Msg-id 471E35B2.7020805@bugs.unl.edu.ar
Whole thread Raw
In response to Re: Bitmap Heap scan 8.1/8.2  (Alvaro Herrera <alvherre@commandprompt.com>)
Responses Re: Bitmap Heap scan 8.1/8.2  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-general
Alvaro Herrera wrote:
>
> It's an arbitrary number, based on which all the other numbers are
> measured.

Now that I read more intensively he docs I see that all the cost
parameters are related one with the other.

> What people generally do around here is mess with random_page_cost, and
> leave seq_page_cost alone.  Often, it's the ratio
> seq_page_cost/random_page_cost what's most important to the cost
> equations results.  (seq_page_cost wasn't tunable at all until
> recently, say 8.1 or 8.2 AFAIR).

Ok, now the 8.1 server has a RAID1 hardware board with SCSI disks, and
the 8.2 is just a PentiumD with SATA disks (it's my desktop PC where I
do tests). Should I have a lower random_page_cost on a machine that is
likely to have a lower disk IO speed?

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