Re: meaning of default_statistics_target

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От Martin Marques
Тема Re: meaning of default_statistics_target
Дата
Msg-id 4815E3F2.2090508@marquesminen.com.ar
обсуждение исходный текст
Ответ на Re: meaning of default_statistics_target  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: meaning of default_statistics_target
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Tom Lane escribió:
> Martin Marques <martin@marquesminen.com.ar> writes:
>> How much, and which extra statistics information will ANALYZE gather if
>> I set a higher value for one specific column (maybe one with and index,
>> and heavily used in SELECT clauses)? If instead of 100 I set a column to
>> 250, which extra data will I see in pg_statistics after an ANALYZE?
>
> The target determines the desired size of the histogram and
> most-common-values arrays.  Increasing it gives you better resolution of
> those stats.
>
> Increasing the target also increases the number of rows that ANALYZE
> samples to prepare the stats, so you should theoretically get more
> accurate stats for the other columns too, even though they'll still get
> boiled down to the same array lengths as before.

Is the value measured in some scale, or does it depend on something
internal? What does 1000 mean?

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