Re: Add important info about ANALYZE after create Functional Index

On Wed, Oct 28, 2020 at 4:35 PM Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
wrote:
>
> I don't think anyone proposed to do this through autovacuum. There was a
> reference to auto-analyze but I think that was meant as 'run analyze
> automatically.' Which would work in transactions just fine, I think.
>

Maybe I was not very clear at the beginning so will try to clarify my
thoughts:

1) We should add notes on our docs about the need to issue ANALYZE after
creating indexes using expressions and create extended statistics. Nikolay
sent a patch upthread and we can work on it and back patch.

2) REINDEX CONCURRENTLY does not keep statistics (pg_statistc) like a
regular REINDEX for indexes using expressions and to me it's a bug. Michael
pointed out upthread that maybe we should rework a bit
index_concurrently_swap() to copy statistics from old index to new one.

> But I agree it'd likely be a more complicated patch than it might seem
> at first glance.
>

If we think about a way to kick AutoAnalyze for sure it will be a more
complicated task but IMHO for now we can do it simply just by copying
statistics like I mentioned above.

Regards,

--
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