Nuno, The number of gets might be the same, but the name of the call used to do the get could be different if there's some code which says: if it's a nice block do X otherwise do Y rather than code that simply says do Y Regards Jonathan Lewis http://jonathanlewis.wordpress.com Author: Cost Based Oracle: Fundamentals http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html The Co-operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html----- Original Message ----- From: "Nuno Souto" <dbvision@xxxxxxxxxxxx>
Cc: <oracle-l@xxxxxxxxxxxxx> Sent: Saturday, July 19, 2008 10:58 AM Subject: Re: Performance off "count(*)"
This was my understanding as well: x$kcbsw shows the same number of blocks, because regardless of count(*) counting the rows in the block header or traversing the row chain in the block, the block itself must be read in both cases. What might be saved is the CPU spent traversing the block. That might be relevant for very small rows and/or very large blocks, with many rows per block?