Re: [HACKERS] Wrong index choosen?

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Tom Lane wrote:

| Dennis Bjorklund <db@zigo.dhs.org> writes:
|
|>In this plan it estimates to get 481 but it got 22477. So the estimation
|>was very wrong. You can increase the statistics tarhet on the login_time
|>and it will probably be better (after the next analyze).
|
|
| Given the nature of the data (login times), I'd imagine that the problem
| is simply that he hasn't analyzed recently enough.  A bump in stats
| target may not be needed, but he's going to have to re-analyze that
| column often if he wants this sort of query to be estimated accurately,
| because the fraction of entries later than a given time T is *always*
| going to be changing.

Well know that I think about it, I felt my shoulders covered by
pg_autovacuum but looking at the log I see that table never analyzed!
Aaargh.

I already applied the patch for the autovacuum but evidently I have to
make it more aggressive, I'm sorry that I can not made him more aggressive
only for this table.


Thank you all.


Regards
Gaetano Mendola









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