From: | Corey Huinker <corey(dot)huinker(at)gmail(dot)com> |
---|---|
To: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> |
Cc: | Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
Subject: | Re: Statistics Import and Export |
Date: | 2023-11-02 05:01:49 |
Message-ID: | CADkLM=cx-XM-PTscj+uDi24x3_vDpYMOjfHgw9CFt_ad5poc0A@mail.gmail.com |
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>
>
>
> Maybe I just don't understand, but I'm pretty sure ANALYZE does not
> derive index stats from column stats. It actually builds them from the
> row sample.
>
That is correct, my error.
>
> > * now support extended statistics except for MCV, which is currently
> > serialized as an difficult-to-decompose bytea field.
>
> Doesn't pg_mcv_list_items() already do all the heavy work?
>
Thanks! I'll look into that.
The comment below in mcv.c made me think there was no easy way to get
output.
/*
* pg_mcv_list_out - output routine for type pg_mcv_list.
*
* MCV lists are serialized into a bytea value, so we simply call byteaout()
* to serialize the value into text. But it'd be nice to serialize that into
* a meaningful representation (e.g. for inspection by people).
*
* XXX This should probably return something meaningful, similar to what
* pg_dependencies_out does. Not sure how to deal with the deduplicated
* values, though - do we want to expand that or not?
*/
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