public inbox for [email protected]
help / color / mirror / Atom feedMultivariate statistics
2+ messages / 2 participants
[nested] [flat]
* Multivariate statistics
@ 2018-07-10 15:57 PG Doc comments form <[email protected]>
2018-08-07 17:44 ` Re: Multivariate statistics Bruce Momjian <[email protected]>
0 siblings, 1 reply; 2+ messages in thread
From: PG Doc comments form @ 2018-07-10 15:57 UTC (permalink / raw)
To: [email protected]; +Cc: [email protected]
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/10/static/multivariate-statistics-examples.html
Description:
Hi All,
I'm a little confused by the documentation here:
https://www.postgresql.org/docs/10/static/multivariate-statistics-examples.html.
In particular, the selectivity of the second query doesn't seem to match up
with what is expected in the notes. I feel like I may be missing something?
(I am referring to the output of this explain command: EXPLAIN (ANALYZE,
TIMING OFF) SELECT * FROM t WHERE a = 1 AND b = 1;)
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: Multivariate statistics
2018-07-10 15:57 Multivariate statistics PG Doc comments form <[email protected]>
@ 2018-08-07 17:44 ` Bruce Momjian <[email protected]>
0 siblings, 0 replies; 2+ messages in thread
From: Bruce Momjian @ 2018-08-07 17:44 UTC (permalink / raw)
To: [email protected]; [email protected]
On Tue, Jul 10, 2018 at 03:57:52PM +0000, PG Doc comments form wrote:
> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/10/static/multivariate-statistics-examples.html
> Description:
>
> Hi All,
>
> I'm a little confused by the documentation here:
> https://www.postgresql.org/docs/10/static/multivariate-statistics-examples.html.
>
>
> In particular, the selectivity of the second query doesn't seem to match up
> with what is expected in the notes. I feel like I may be missing something?
>
>
> (I am referring to the output of this explain command: EXPLAIN (ANALYZE,
> TIMING OFF) SELECT * FROM t WHERE a = 1 AND b = 1;)
Uh, the first query shows an _estimate_ of rows=1, which does not match
the actual rows=100:
Seq Scan on t (cost=0.00..195.00 rows=1 width=8) (actual rows=100 loops=1)
The second query has it right:
Seq Scan on t (cost=0.00..195.00 rows=100 width=8) (actual rows=100 loops=1)
--
Bruce Momjian <[email protected]> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ As you are, so once was I. As I am, so you will be. +
+ Ancient Roman grave inscription +
^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2018-08-07 17:44 UTC | newest]
Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2018-07-10 15:57 Multivariate statistics PG Doc comments form <[email protected]>
2018-08-07 17:44 ` Bruce Momjian <[email protected]>
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox