Re: pg_freespacemap question

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От Tatsuo Ishii
Тема Re: pg_freespacemap question
Дата
Msg-id 20060312.084023.91756133.t-ishii@sraoss.co.jp
обсуждение исходный текст
Ответ на Re: pg_freespacemap question  (Mark Kirkwood <markir@paradise.net.nz>)
Ответы Re: [PATCHES] pg_freespacemap question  (Tatsuo Ishii <ishii@sraoss.co.jp>)
Список pgsql-hackers
Mark,

I have tried your patches and it worked great. Thanks.
--
Tatsuo Ishii
SRA OSS, Inc. Japan

> Tom Lane wrote:
> > Mark Kirkwood <markir@paradise.net.nz> writes:
> >
> >>>Good points! I had not noticed this test case. Probably NULL is better
> >
> >
> >>Would setting it to 'BLCKSZ - (fixed index header stuff)' be better,
> >
> >
> > No, I don't think so, because that will just make it harder to recognize
> > what's what (remember that BLCKSZ isn't really a constant, and the index
> > overhead is not the same for all AMs either).  The point here is that
> > for indexes the FSM tracks whole-page availability, not the amount of
> > free space within pages.  So I think NULL is a reasonable representation
> > of that.  Using NULL will make it easy to filter the results if you want
> > to see only heap-page data or only index-page data, whereas it will be
> > very hard to do that if the view adopts an ultimately-artificial
> > convention about the amount of available space on an index page.
> >
>
> Right - after suggesting it I realized that coding the different index
> overhead for each possible AM would have been ... difficult :-). A patch
> is attached to implement the NULL free bytes and other recommendations:
>
> 1/ Index free bytes set to NULL
> 2/ Comment added to the README briefly mentioning the index business
> 3/ Columns reordered more logically
> 4/ 'Blockid' column removed
> 5/ Free bytes column renamed to just 'bytes' instead of 'blockfreebytes'
>
> Now 5/ was only hinted at, but seemed worth doing while I was there
> (hopefully I haven't made it too terse now....).
>
> cheers
>
> Mark
>

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