Re: Bad performance because of wrong characterset?

Hi!

Only string manipulation/comparision is slower with variable width charsets than with fixed width ones, because with variable width ones (UTF-8) you have to check the highest bit of each byte to check whether it shows that the next byte is "part of" current character or is part of next character. So, this means more CPU usage.

But, if you migrate your whole database from UTF-8 to UTF-16 and you got a lot of character data, your database overall performance might get worse, since your strings get larger in bytes and retrieving 100 rows might mean reading 20 blocks instead of 10 like in the past.

Performance depends on a lot of things, such how much string operations you got, what are the contents of your strings (are they mainly latin chars or are there lots of asian ones etc..).

Tanel.

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Monday, November 17, 2003 4:54 PM

> Carel-Jan,
>
> About two weeks ago, Faan DeSwardt <Faan_D1_at_VERIFONE.com> posted to the
thread
> "Unicode: UTF-16 to UTF-8 conversion", saying UTF-8 is variable-length
encoding
> and so is slower than the fixed-width UTF-16, and also US7ASCII. Maybe
it's the
> same issue here comparing UTF-8 with WE8ISO8859P15. Faan can comment.
>
> Yong Huang
>
> --- Carel-Jan Engel <cjpengel.dbalert_at_xs4all.nl> wrote:
> > Hi List,
> >
> > One of my customers gets HP Servicedesk 4.5 implemented. The database
that
> > has been created by on of the DBA's for the application is Oracle
8.1.7.4,
> > on AIX 4.3.
> >
> > The database has characterset UTF8, which is the standard here.
> >
> > Now ServiceDesk has bad performance. HP claims that the characterset is
> > wrong, and a new database has to be created with character set
> > WE8ISO8859P15.
> >
> > I've never heard of bad performance due to differences in character
sets,
> > probably because of my lack of experience. Anyone familiar with this
> > issue?
> >
> > TIA, Carel-Jan
>
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-- 
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-- 
Author: Tanel Poder
  INET: tanel.poder.003_at_mail.ee

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