Re: Gin indexes on intarray is fast when value in array does not exists, and slow, when value exists

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От otar shavadze
Тема Re: Gin indexes on intarray is fast when value in array does not exists, and slow, when value exists
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Msg-id CAG-jOyA99+cr1EOkoNj0Q6wfNGMkrKpHSfLs4SHiV=GC5AKxQA@mail.gmail.com
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Ответ на Re: Gin indexes on intarray is fast when value in array does not exists, and slow, when value exists  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: Gin indexes on intarray is fast when value in array does not exists, and slow, when value exists  (Tom Lane <tgl@sss.pgh.pa.us>)
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@Jeff
 
most_common_elems.  Is it empty, or is it not empty?  If not empty, does it contain the specific values you used in your queries?

No, most_common_elems is not empty. it contain the specific values I used in queries.



@Tom

Hmmm ... actually, I wonder if maybe '@>' here is the contrib/intarray
operator not the core operator?  The intarray operator didn't get plugged
into any real estimation logic until 9.6.


So, you mean that better would be go to version 9.6 ?

On Wed, Nov 9, 2016 at 8:35 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
I wrote:
> Seems like your problem here is that the planner has no idea about the
> selectivity of this condition --- if it did, I think it would have
> made the right choice, because it would have made a much higher estimate
> for the cost of the indexscan.

> AFAICT, Postgres 9.5 does make a reasonably correct guess when given
> up-to-date stats.  I speculate that you need to ANALYZE this table.

Hmmm ... actually, I wonder if maybe '@>' here is the contrib/intarray
operator not the core operator?  The intarray operator didn't get plugged
into any real estimation logic until 9.6.

                        regards, tom lane

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