Re: time of select

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Wed, 18 Oct 2000 10:54:15 +0100
Message-ID: <971863920.587.0.nnrp-10.9e984b29@news.demon.co.uk>

You did say 'MYVIEW'. not 'MYTABLE', so there is likely to be a non-trivial execution path, and (e and oe) most lines will have a 'cost, cardinality' and 'bytes' columns. It is these intermediate figures that Conor would have in mind, not the fact that the ultimate output is guaranteed to be just one line.

Even 'select max(mycol) from mytable' could give you some cardinality information, e.g. in a 'table (FULLSCAN)' line

--

Jonathan Lewis
Yet another Oracle-related web site:  http://www.jlcomp.demon.co.uk

Andreas Koch wrote in message
<39EB788B.A68F4A30_at_rbg.informatik.tu-darmstadt.de>...


>

>

>Connor McDonald schrieb:

>

>> > how can i know how long a "select max(mycol) from myview" will take -

>> > BEFORE it is finished?

>>

>> You could issue an explain plan and check the estimated rows count and

>> make an educated guess from that...

>

>The problem is, the select will return ONE row.

>

>--

>                                                 Andreas

>Techniker:Nein, dieser Kopierer hat keinen automatischen

>Einzug. Das sind die Lüftungsschlitze.

>

Received on Wed Oct 18 2000 - 04:54:15 CDT