Re: Postgres not using correct indices for views. - Mailing list pgsql-performance

From Tom Lane
Subject Re: Postgres not using correct indices for views.
Date
Msg-id 27100.1565304307@sss.pgh.pa.us
Whole thread Raw
In response to Re: Postgres not using correct indices for views.  ("Thomas Rosenstein" <thomas.rosenstein@creamfinance.com>)
List pgsql-performance
"Thomas Rosenstein" <thomas.rosenstein@creamfinance.com> writes:
> The planner estimates the correct row counts, but still does the wrong 
> planning.

Hm, I'm not exactly convinced.  You show

> Wrong:
>           ->  Hash Join  (cost=359555.11..1849150.95 rows=1496816 
> width=1508) (actual time=1081.081..24251.466 rows=543231 loops=1)
>                 Hash Cond: (p.customer_id = l.customer_id)
>                 Join Filter: ((p.date - '3 days'::interval day) <= 
> l.duedate)
>                 Rows Removed by Join Filter: 596120

> Correct:
>     ->  Nested Loop  (cost=0.87..2961441.25 rows=515233 width=1471)

The join size estimate seems a lot closer to being correct in the
second case, which could lend support to the idea that statistics
aren't being applied in the first case.

However ... it sort of looks like the planner didn't even consider
the second plan shape in the "wrong" case.  If it had, then even
if it costed it 3X more than it did in the "right" case, the second
plan would still have won out by orders of magnitude.  So there's
something else going on.

Can you show the actual query and table and view definitions?

            regards, tom lane



pgsql-performance by date:

Previous
From: "Thomas Rosenstein"
Date:
Subject: Re: Postgres not using correct indices for views.
Next
From: Rob Emery
Date:
Subject: Bitmap heap scan performance