Re: slow query, different plans

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

 



"Midge Brown" <midgems@xxxxxxxxxxxxx> writes:
> I'm having a problem with a query on our production server, but not on a laptop running a similar postgres version with a recent backup copy of the same table. I tried reindexing the table on the production server, but it didn't make any difference. Other queries on the same table are plenty fast. 

Reindexing won't help that.  The problem is a bad statistical estimate;
it thinks there are about 700 rows with applies2 = 256, when there's
really only one.  That means the "fast" plan is a lot faster than the
planner gives it credit for, and conversely the "slow" plan is a lot
slower than the planner is expecting.  Their estimated costs end up
nearly the same, which makes it a bit of a chance matter which one is
picked --- but the true costs are a lot different.  So you need to fix
that rowcount estimate.  Raising the stats target for the table might
help.

			regards, tom lane

-- 
Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance


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

  Powered by Linux