select count(*) on large tables

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От Cosimo Streppone
Тема select count(*) on large tables
Дата
Msg-id 40751ED5.1010208@streppone.it
обсуждение исходный текст
Ответы Re: select count(*) on large tables  (Dennis Bjorklund <db@zigo.dhs.org>)
Re: select count(*) on large tables  (Tom Lane <tgl@sss.pgh.pa.us>)
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Hello,

I've followed the last discussion about the particular case of
"select count(*)"s on large tables being somewhat slow.

I've seen also this issue already on the todo list, so I know
it is not a simple question.
This problem arises for me on very large tables, which I mean
starting from 1 million rows and above.

The alternative solution I tried, that has an optimal
speed up, unfortunately is not a way out, and it is based
on "EXPLAIN SELECT count(*)" output parsing, which
is obviously *not* reliable.

The times always get better doing a vacuum (and eventually
reindex) of the table, and they slowly lower again.

Is there an estimate time for this issue to be resolved?
Can I help in some way (code, test cases, ...)?

--
Cosimo


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