Re: extending relations more efficiently

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Wed, May 2, 2012 at 12:26 PM, Alvaro Herrera
> <alvherre(at)commandprompt(dot)com> wrote:
>> Hm. I see those two things as different -- to me, bloat is unremoved
>> dead tuples, whereas slack space would be free space that can be reused
>> by new tuples. Slack space is useful as it avoids relation extension;
>> bloat is not.

> I guess I think of bloat as including both unremoved dead tuples and
> unwanted internal free space. If you create a giant table, delete 9
> out of every 10 tuples, and vacuum, the table is still "bloated", IMV.

The difficulty is to tell the difference between useless free space and
useful free space. If there's a reasonable probability of putting new
data into a given chunk of free space in the near future, it's not
bloat.

regards, tom lane