Re: Performance off "count(*)"
From: Greg Rahn <greg_at_structureddata.org>
Date: Fri, 18 Jul 2008 14:44:15 -0700
Message-ID: <a9c093440807181444q328cb1ccqd4f223eec2d88625@mail.gmail.com>
> Am I correct in my "small understanding" of Oracle that "count(*)" has
> been optimized.
Date: Fri, 18 Jul 2008 14:44:15 -0700
Message-ID: <a9c093440807181444q328cb1ccqd4f223eec2d88625@mail.gmail.com>
On Fri, Jul 18, 2008 at 10:28 AM, Marco Gralike <Marco.Gralike_at_amis.nl> wrote:
>
> Am I correct in my "small understanding" of Oracle that "count(*)" has
> been optimized.
A count(*) that uses TABLE ACCESS FULL access does not have to read each block in its entirety, it just reads the header to see how many rows are in the block. I guess you could call that "optimized".
-- Regards, Greg Rahn http://structureddata.org -- http://www.freelists.org/webpage/oracle-lReceived on Fri Jul 18 2008 - 16:44:15 CDT