On Mon, Jan 13, 2020 at 05:32:53PM +0100, Tomas Vondra wrote:
> On Mon, Jan 13, 2020 at 11:08:40AM +0300, Konstantin Knizhnik wrote:
> >
> >"if any code tried to access the statistics directly from the table,
> >rather than via the caches".
> >
> >Currently optimizer is accessing statistic though caches. So this
> >approach works. If somebody will rewrite optimizer or provide own
> >custom optimizer in extension which access statistic directly
> >then it we really be a problem. But I wonder why bypassing catalog
> >cache may be needed.
> >
>
> I don't know, but it seems extensions like hypopg do it.
AFAIR, hypopg only opens pg_statistic to use its tupledesc when creating
statistics on hypothetical partitions, but it should otherwise never reads or
need plain pg_statistic rows.