Re: [PATCHES] pg_freespacemap question - Mailing list pgsql-hackers

From Mark Kirkwood
Subject Re: [PATCHES] pg_freespacemap question
Date
Msg-id 4414F6EC.7010909@paradise.net.nz
Whole thread Raw
In response to Re: [PATCHES] pg_freespacemap question  (Christopher Kings-Lynne <chriskl@familyhealth.com.au>)
Responses Re: [PATCHES] pg_freespacemap question  (Alvaro Herrera <alvherre@commandprompt.com>)
List pgsql-hackers
Christopher Kings-Lynne wrote:
>> The point here is that if tuples require 50 bytes, and there are 20
>> bytes free on a page, pgstattuple counts 20 free bytes while FSM
>> ignores the page.  Recording that space in the FSM will not improve
>> matters, it'll just risk pushing out FSM records for pages that do
>> have useful amounts of free space.
>
>
>
> Maybe an overloaded pgstattuple function that allows you to request FSM
> behavior?
>

That's a nice idea - could also do equivalently by adding an extra
column "usable_free_space" or some such, and calculating this using FSM
logic.

Cheers

Mark


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