Re: Lies, damn lies and statistics

Stephane,

Three things I don't need to tell you about your example:

Prior to CPU-costing in 9, the order of
single table predicates can have a dramatic impact on CPU without changing the amount of logical I/O.

Logical I/O should always include the statistics "buffer is pinned count" - it's just another way of visiting a buffer - the cost of getting there is cheaper, but still not free.

Any change to the query could modify
the number of times a pl/sql function is called - which could be far more CPU intensive than all the logical I/O effects anyway.

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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The Co-operative Oracle Users' FAQ
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• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: 01 April 2003 22:14

> Here is the result :
>
> original all_rows
> Steps in plan 176 166
> recursive calls 259 1776
> db block gets 72 324
> consistent gets 474556 6700
> physical reads 12497 1981
> redo size 152 21736
> bytes to client 3060 3060
> bytes from client 5811 4500
> SQL*Net roundtrips 2 2
> memory sorts 10 13
> disk sorts 0 0
> rows 6 6
> Elapsed time 24.75 > 4 mn
>
> Although LIOs have drastically reduced, and so have PIOs, our time
is
> about 10 times worse!

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Author: Jonathan Lewis
  INET: jonathan_at_jlcomp.demon.co.uk

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