Where case when query not running at all in 11.2.0.3

Question

Hi,
I have a query that was running fine till the time we were in 11.1.0.7. Last month, we had a migration to 11.2.0.3, and the query has stopped running since then. It runs indefinitely, and finally I have to kill it. However, until 11.1.0.7, I had absolutely no problems with it. Not sure what changed in 11.2.0.3 that causes it to never give me a result. The query is as below:
SELECT T1.NAME,T2.AGE,T2.level, T2.AMT,
FROM table1 T1, table2 T2
WHERE (CASE WHEN
(T1.name = 'Peter' AND SUBSTR(T1.desc,1,15)=SUBSTR(T2.description,1,15))
THEN 1
ELSE 0
END)=1;
Please advise!
Thanks in advance.

Answer 1

Hi,
CrazyAnie wrote:
Hi,
I have a query that was running fine till the time we were in 11.1.0.7. Last month, we had a migration to 11.2.0.3, and the query has stopped running since then. It runs indefinitely, and finally I have to kill it. However, until 11.1.0.7, I had absolutely no problems with it. Not sure what changed in 11.2.0.3 that causes it to never give me a result. The query is as below:
SELECT T1.NAME,T2.AGE,T2.level, T2.AMT,
FROM table1 T1, table2 T2
WHERE (CASE WHEN
(T1.name = 'Peter' AND SUBSTR(T1.desc,1,15)=SUBSTR(T2.description,1,15))
THEN 1
ELSE 0
END)=1;
Please advise!I'm surprised it runs in any version. You have a comma right before the keyword FROM. If you were not getting a compile-time error, that was a bug in 11.1.0.7 that they fixed by 11.2.0.3.
It's still strange that the query runs for a long time. I would expect it to give you an error when you tried to compile it. Is there any chance that what you posted is not what you're actually running?
Also, LEVEL, NAME and DESC are not good column names. How Oracle reacts to using keywords like that as column names can vary from version to version. If a word is in v$reserved_words.keyword, then it's best to avoid using it as a column (or table, or variable, or schema) name.
Edited by: Frank Kulash on Nov 21, 2012 1:33 PM
By the way, that WHERE clause is a lot more complicated than it needs to be. Why not use
WHERE      t1.name = 'Peter'
AND      SUBSTR ( t1."DESC"     -- If you must use DESC, double-quote it
            , 1
            , 15
            ) = SUBSTR ( t2.description
                           , 1
                 , 15
                 )? Always think carefully before using CASE in a WHERE (or HAVING, or START WITH, or CONNECT BY) clause.