On Mon, Oct 18, 2021, at 8:53 PM, Alvaro Herrera wrote:
On 2021-Oct-18, David G. Johnston wrote:
> wrote:
> > Given that the first stage uses statistic target=1, running this option
> > in a database with any stats at all is probably a bad idea.
>
> Add the word "only"?
>
> This option is only useful to analyze a database...
Maybe this is sufficient, since it would drive people away from trying
to do anything else than help upgrades with it.
+1. I like your 2nd suggestion.
"This option is only useful to analyze a database that was newly populated from
a restored dump or by <command>pg_upgrade</command>. Beware that running with
this option in a database with existing statistics may cause query optimizer
choices to become transiently worse, because of the very low statistics target
that is used in the early stages."
> "Run several (currently three) stages of analyze with different
> configuration settings, to produce usable statistics faster. The first of
> these stages will remove any existing statistics even if they use a larger
> statistic target configuration."
.. yeah, this is another option.
We might include it too but I would suggest "replace" instead of "remove"
because it seems there won't be statistics after the first stage.