From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Jeroen Vermeulen <jtv(at)xs4all(dot)nl>, Andres Freund <andres(at)anarazel(dot)de>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: extending relations more efficiently |
Date: | 2012-05-02 16:45:35 |
Message-ID: | 13539.1335977135@sss.pgh.pa.us |
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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
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