[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: query optimization

Richard Kojedzinszky <krichy@xxxxxxxxxxxx> writes:
> Dear list,
> We have a database schema, which looks the same as the attached script.

> When filling the tables with data, and skipping analyze on the table (so 
> pg_stats contains no records for table 'a'), the first select in the 
> script runs fast, but after an analyze the planner decides to sequence 
> scan tables b and c, thus making the query much slower. Can somebody help 
> me solving this issue, or tuning our installation to not to use sequence 
> scans in this case?

Um ... did you analyze all the tables, or just some of them?  I get
sub-millisecond runtimes if all four tables have been analyzed, but it
does seem to pick lousy plans if, say, only a and b have been analyzed.

What you really need for this query structure is the parameterized-path
work I've been doing for 9.2; but at least on the exact example given,
I'm not seeing that 9.1 is that much worse.

			regards, tom lane

Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx)
To make changes to your subscription:

[Postgresql General]     [Postgresql PHP]     [PHP Users]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Home]     [Yosemite]

Powered by Linux