Re: Maximum reasonable free space map - Mailing list pgsql-general

From Greg Stark
Subject Re: Maximum reasonable free space map
Date
Msg-id 4136ffa0812170528t440d9fael2903129795798c51@mail.gmail.com
Whole thread Raw
In response to Re: Maximum reasonable free space map  ("Scott Marlowe" <scott.marlowe@gmail.com>)
List pgsql-general
On Wed, Dec 17, 2008 at 5:45 AM, Scott Marlowe <scott.marlowe@gmail.com> wrote:
>
> If you've got 40M rows and 10% are updated each day, then it's likely
> you'll want 4M fsm entries avaialble for those dead rows.

FWIW you only need an entry for each *page* of the table, not every
row. Of course if you have 40M rows and 10% are updated each day they
might all be on different pages. Also, it's not really the end of the
world if the FSM doesn't track every single page with free space -- as
long as it tracks enough to cover your usage until the next vacuum.

Thankfully all this is gone in 8.4.

--
greg

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