Re: vacuumdb --analyze-in-stages
| От | Euler Taveira |
|---|---|
| Тема | Re: vacuumdb --analyze-in-stages |
| Дата | |
| Msg-id | 3907a55d-a40f-4566-9906-150fca10f0df@www.fastmail.com обсуждение исходный текст |
| Ответ на | Re: vacuumdb --analyze-in-stages (Alvaro Herrera <alvherre@alvh.no-ip.org>) |
| Ответы |
Re: vacuumdb --analyze-in-stages
|
| Список | pgsql-docs |
On Mon, Oct 18, 2021, at 8:53 PM, Alvaro Herrera wrote:
On 2021-Oct-18, David G. Johnston wrote:> On Mon, Oct 18, 2021 at 4:02 PM Alvaro Herrera <alvherre@alvh.no-ip.org>> 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 tryingto 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.
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