Re: heap_page_prune comments - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: heap_page_prune comments
Date
Msg-id 20120816230308.GD30286@momjian.us
Whole thread Raw
In response to heap_page_prune comments  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
On Wed, Nov  2, 2011 at 12:27:02PM -0400, Robert Haas wrote:
> The following comment - or at least the last sentence thereof -
> appears to be out of date.
> 
>         /*
>          * XXX Should we update the FSM information of this page ?
>          *
>          * There are two schools of thought here. We may not want to update FSM
>          * information so that the page is not used for unrelated
> UPDATEs/INSERTs
>          * and any free space in this page will remain available for further
>          * UPDATEs in *this* page, thus improving chances for doing HOT updates.
>          *
>          * But for a large table and where a page does not receive
> further UPDATEs
>          * for a long time, we might waste this space by not updating the FSM
>          * information. The relation may get extended and fragmented further.
>          *
>          * One possibility is to leave "fillfactor" worth of space in this page
>          * and update FSM with the remaining space.
>          *
>          * In any case, the current FSM implementation doesn't accept
>          * one-page-at-a-time updates, so this is all academic for now.
>          */
> 
> The simple fix here is just to delete that last sentence, but does
> anyone think we ought to do change the behavior, now that we have the
> option to do so?

Last sentence removed.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + It's impossible for everything to be true. +



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