Re: [PERFORM] change sample size for statistics

[Willy-Bas Loos <willybas@xxxxxxxxx>]

On Fri, Jun 10, 2011 at 9:58 PM, Josh Berkus <josh@xxxxxxxxxxxx> wrote:

It's not 10%.  We use a fixed sample size, which is configurable on the

system, table, or column basis.

It seems that you are referring to "alter column set statistics" and "default_statistics_target", which are the number of percentiles in the histogram  (and MCV's) .

I mean the number of records that are scanned by analyze to come to the statistics for the planner, especially n_disctict.

On Fri, Jun 10, 2011 at 10:06 PM, Nathan Boley <npboley@xxxxxxxxx> wrote:

If you need to fix ndistinct, a better approach may be to do it manually.

That would be nice, but how do i prevent the analyzer to overwrite n_distinct without blocking the generation of new histogram values etc for that column?

We use version 8.4 at the moment (on debian squeeze).

Cheers,

WBL

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