Re: JDBC and SQL Performance Under V5R3 -- JAVA400-L

Ed,

I don't know, and I'd be extremely interested to hear anyone's experience
on the matter as well.  We have very similar problems, currently at V5R2.
The website currently does some horrid queries, even 'equals' searches must
be space and case insensitive, so do "WHERE
LTRIM(RTRIM(UCASE(FIELDNAME)))='VALUE'" and as such make terrible (or no)
use of indexes/logical access paths.  We're looking to get around this by
duplicating the field in the table, once in its original form and once as
an already trimmed and upper cased copy of the field.  Then we can build an
index/logical access path over the trimmed and upper cased copy of the
field and the queries simply becomes "WHERE NEWFIELD='VALUE'" - the
performance improvement from doing this is enormous, anything from 4x to
200x on some queries.

The LIKE keyword is a bit more tricky, from what I can tell if you do a
'starts with' type query (such as WHERE FIELDNAME LIKE 'XYZ%') the database
will be able to make efficient use of an index sorted on that field, but if
you do a 'contains' type query (such as WHERE FIELDNAME LIKE '%XYZ%') then
you're basically out of luck no matter what, since there's no index that
will ever run this quickly, the database has to check every record one at a
time.  Although we've proved that "WHERE FIELDNAME LIKE '%XYZ%'" is still a
significant improvement over "WHERE UCASE(FIELDNAME) LIKE '%XYZ%'"

So I'd also appreciate any info anybody has with SQL queries on V5R3!

Thanks,

Nigel Gay.
Computer Patent Annuities.



|---------+------------------------------>
|         |           EDoxtator          |
|         |           <doc6502@xxxxxxxxx>|
|         |           Sent by:           |
|         |           java400-l-bounces@m|
|         |           idrange.com        |
|         |                              |
|         |                              |
|         |           03/11/2004 11:54 AM|
|         |           Please respond to  |
|         |           Java Programming on|
|         |           and around the     |
|         |           iSeries / AS400    |
|         |                              |
|---------+------------------------------>
  
>--------------------------------------------------------------------------------------------------------------|
  |                                                                             
                                 |
  |       To:       java400-l@xxxxxxxxxxxx                                      
                                 |
  |       cc:                                                                   
                                 |
  |       Subject:  JDBC and SQL Performance Under V5R3                         
                                 |
  
>--------------------------------------------------------------------------------------------------------------|




All

I'm working at a client right now who is using OS/400 V5R1 and client has
written a series of Java (JDK 1.4) with WSDS, and is seeing some fairly
awful
performance issues.

I've suggested some things (limiting the use of the like keyword, using
existing logical file access paths, etc), but they've got a huge amount of
data
(2 TB) to sift through.

>From what I have read from IBM, there are significant gains to be made in
overall SQL performance in V5R3.

Are these claims valid?  Has anyone been using V5R3?

Thanks

-Ed
--
This is the Java Programming on and around the iSeries / AS400 (JAVA400-L)
mailing list
To post a message email: JAVA400-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/java400-l
or email: JAVA400-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at http://archive.midrange.com/java400-l.








********************************************************************************
The information in this message is confidential and may be legally
privileged. It is intended solely for the addressee; access to this
email by anyone else is unauthorised.

If you are not the intended recipient: (1) you are kindly requested
to return a copy of this message to the sender indicating that you
have received it in error, and to destroy the received copy; and (2)
any disclosure or distribution of this message, as well as any action
taken or omitted to be taken in reliance on its content, is prohibited
and may be unlawful.
********************************************************************************