RE: SQL Operation and Row size

[Grant Allen]

> -Original Message-
> From: Stephane Faroult [mailto:[EMAIL PROTECTED]
> Sent: Thursday, 16 October 2003 07:14
> To: Multiple recipients of list ORACLE-L
> Subject: Re: SQL Operation and Row size
> 
> 
> Daniel Fink wrote:
> > 
> > When retrieving data, does Oracle place just the columns of
> > interest into the result set or does it place the entire row in
> > the result set (and filter out the columns of interest later)?
> > 
> 
> I'd say just the columns of interest. Can be checked by looking at the
> number of buffer gets on a table with some noticeable chaining,
> comparing select * to select pkcol.

Following on from this, I've always been curious where result sets that include 
computed or literal values get stored.  It's not possible to cache the block of 
something that was never in a block to begin with (though I'm willing to be corrected 
on that :-)).  Would it be a temp segment created for just the computed/literal 
values; temp segments for the whole result set; somewhere in UGA/PGA; or somewhere 
else entirely?  Any light shed on this would satisfy my curiosity.

Ciao
Fuzzy
:-)
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Author: Grant Allen
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Re: SQL Operation and Row size

[Stephane Faroult]

Daniel Fink wrote:
> 
> When retrieving data, does Oracle place just the columns of
> interest into the result set or does it place the entire row in
> the result set (and filter out the columns of interest later)?
> 

I'd say just the columns of interest. Can be checked by looking at the
number of buffer gets on a table with some noticeable chaining,
comparing select * to select pkcol.

-- 
Regards,

Stephane Faroult
Oriole Software
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RE: SQL Operation and Row size

[Stephane Paquette]

At what step ?

Oracle reads blocks, so from the datafile up to the db_buffer/db_cache its
blocks.
It would be logical that the filtering occurs after the where clause has
chosen the data matching the search criteria, so in the select step which is
the last step of the query operation.


Stephane Paquette
Administrateur de bases de donnees
Database Administrator
Standard Life
www.standardlife.ca
Tel. (514) 499-7999 7470 and (514) 925-7187

[EMAIL PROTECTED] 




-Original Message-
Daniel Fink
Sent: 15 octobre, 2003 16:09
To: Multiple recipients of list ORACLE-L


When retrieving data, does Oracle place just the columns of
interest into the result set or does it place the entire row in
the result set (and filter out the columns of interest later)?

--
Please see the official ORACLE-L FAQ: http://www.orafaq.net
--
Author: Daniel Fink
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-- 
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-- 
Author: Stephane Paquette
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