FROM fwepcode1
WHERE (wotype = 'TST' AND func = 'C0NEPRF' AND EXP = '22222')
OR not exists(select 1 FROM valuelist
WHERE listname = 'STATUS'
AND MAXVALUE = 'AAAAA'
Tom Mercadante
Oracle Certified Professional
-----Original Message-----
From: Denham Eva [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, January 14, 2003 6:29 AM
To: Multiple recipients of list ORACLE-L
Subject: slowish query causing problems...Hello List,
Pls help me on this problem. Our application does a validation when it uses a certain screen, as it so happens this screen is used very intensively. The performance is very slow, I have isolated the main culprit. I have tried the following.
I have dropped all the indexes and tried recreating them individually. Each time I have run an explain plan on the query, the optimizer (both rule and Choose) have chosen to do a FULL table scan on the fwepcode table. Even when using a hint to explicitly use the index it still uses FULL.
This is very frustrating indeed.
SELECT DISTINCT (1)
FROM fwepcode1
WHERE (wotype = 'TST' AND func = 'C0NEPRF' AND EXP = '22222')
OR 'INPRG' NOT IN (SELECT VALUE
FROM valuelist
WHERE listname = 'STATUS'
AND MAXVALUE = 'AAAAA')Is the reason that the optimizer does not use any of the indexes because of the SELECT DISTINCT (1)?
I have tried adjusting this query slightly to remove this and it still insists on doing a full table scan.
Funny enough the sub query on valuelist table does use a index.
The table contains 8920 rows. The cost according to the explain plan is 703 and bytes 9834.The system is a Oracle 817 on Win2k.
Pls advise, any options or help will be appreciated.
Many Thanks
Denham Eva
Oracle DBA
"UNIX is basically a simple operating system, but you have to be a genius to understand the simplicity."
Dennis Ritchie.
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