Re: Slow count(*) again...

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

 



On Tue, Oct 12, 2010 at 1:07 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote:
> Anyway, if anyone is hot to make COUNT(*) faster, that's where to look.
> I don't think any of the previous discussion in this thread is on-point
> at all, except for the parts where people suggested avoiding it.

I kind of hope that index-only scans help with this, too.  If you have
a wide table and a narrow (but not partial) index, and if the
visibility map bits are mostly set, it ought to be cheaper to read the
index than the table - certainly in the case where any disk I/O is
involved, and maybe even if it isn't.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

-- 
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