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Posted to log4j-dev@logging.apache.org by Simon Dorrat <si...@gsjbw.com> on 2004/06/21 02:45:38 UTC

RE: logging_event_property column sizes

Just came across this email, hope its not too late.  I would definitely
recommend using Varchars.  The space saving gained multiplies as it affects
indexes too, and that then translates into much better performance.
Especially when you have potentially very long keys (like the 254 chars you
mentioned).

Most sophisticated dbs should cope with variable length records fine,
optimising storage when it has to.   Generally any performance improvement
from fixed length records here would be less than the overall space and
performance penalty.

Something to consider too: better to use the VARCHAR2 column type with
Oracle.  VARCHAR is currently synonymous with VARCHAR2, but is reserved for
future use, so could change in the future.  (The history of the
VARCHAR/VARCHAR2 columns is a bit of a laughable debacle).

Simon

> -----Original Message-----
> From:	Paul Smith [SMTP:Paul.Smith@lawlex.com.au]
> Sent:	Saturday, 15 May 2004 10:38 AM
> To:	'James Stauffer '; ''log4j-dev@logging.apache.org' '
> Subject:	RE: logging_event_property column sizes
> 
> Actually, if the coumn is a varchar one, then no space is wasted from what
> I
> remember. Only the exact # chars for the row is allocated.
> 
> Having said that, I can speak from my own personal experience with some
> DB's
> when I recommend an actual fixed size column (char).  If you can get a
> table's row size to be exactly the same for each row, then most db's can
> optimize retrievals, particularly with table scans.  YMMV of course.
> 
> I agree that 254 for values seems a bit small, but I would'nt recommend
> making it smaller for the key size either, you'd be surprised how quickly
> someone would run in to that limit.
> 
> 
> cheers,
> 
> Paul Smith
> 
> -----Original Message-----
> From: James Stauffer
> To: 'log4j-dev@logging.apache.org'
> Sent: 5/14/04 11:31 PM
> Subject: logging_event_property column sizes
> 
> In logging_event_property both mapped_key and mapped_value are 254
> characters. 
> I don't think I have any keys longer than about 10 characters but I do
> have values more than 254 characters. 
> What would you think of decreasing mapped_key to something like 32 (this
> isn't important to me but 254 seems like a waste of space) and
> increasing mapped_value to 510 or 1022 (assuming that 254 was chosen as
> 2 less than a power of 2)?
> 
> James Stauffer 
> 
> 
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