Re: Measuring relation free space
От | Noah Misch |
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Тема | Re: Measuring relation free space |
Дата | |
Msg-id | 20120116100931.GA29684@tornado.leadboat.com обсуждение исходный текст |
Ответ на | Re: Measuring relation free space (Jaime Casanova <jaime@2ndquadrant.com>) |
Ответы |
Re: Measuring relation free space
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Список | pgsql-hackers |
On Sat, Jan 14, 2012 at 02:40:46PM -0500, Jaime Casanova wrote: > On Sat, Jan 14, 2012 at 6:26 AM, Noah Misch <noah@leadboat.com> wrote: > > > > - pgstattuple() and relation_free_space() should emit the same number, even if > > ?that means improving pgstattuple() at the same time. > > yes, i just wanted to understand which one was more accurate and > why... and give the opportunity for anyone to point my error if any pgstattuple()'s decision to treat half-dead pages like deleted pages is better. That transient state can only end in the page's deletion. I don't know about counting non-leaf pages, but I personally wouldn't revisit pgstattuple()'s decision there. In the indexes I've briefly surveyed, the ratio of leaf pages to non-leaf pages is 100:1 or better. No amount of bloat in that 1% will matter. Feel free to make the argument if you think otherwise, though; I've only taken a brief look at the topic. > > - relation_free_space() belongs in the pgstattuple extension, because its role > > ?is cheaper access to a single pgstattuple() metric. > > oh! right! so, what about just fixing the free_percent that > pgstattuple is providing If pgstattuple() meets your needs, you might indeed no longer need any patch.
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