Query runs for ever - suggestions - ideas - tips

Question

Hello all,
I have the following situation:
1) Database 1: XE 10g Release 10.2.0.1.0 - Production
2) Database 2: 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
3) Dblink from Database 1 pointing to Database 2
4) Synonyms created withing Database 1, pointing to Database 2 packages and tables:
- "mytable1" exists in Database 2 therefore a synonym "mytable1" is created in Database 1
- "mytable2" exists in Database 2 therefore a synonym "mytable2" is created in Database 1
- "mypackage" exists in Database 2 therefore a synonym "mypackage" is created in Database 1
5) Of course select and execute rights are granted
6) Query:
SELECT field1
FROM myshcema.mytable1
WHERE field2 = myshcema.mypackage.myfunction ('PARAMVALUE'))
AND EXISTS (SELECT 1 FROM myshcema.mytable2 WHERE field_in_tab2 = field_in_tab1)
7) Problem.This query runs for ever
8) Explain plan
OPERATION - OBJECT_NAME - OPTIONS - COST
SELECT STATEMENT - - - 17
-> FILTER - - -
-> -> FILTER - - - 3
-> -> -> REMOTE - mytable1 - -
-> -> REMOTE - mytable2 - - 1
9) Now I get the value returned by the function and re-execute the previous query:
- select myshcema.mypackage.myfunction ('PARAMVALUE')) from dual;
- return value is *89787621*
- re-executing the query:
SELECT field1
FROM myshcema.mytable1
WHERE field2 = *89787621*
AND EXISTS (SELECT 1 FROM myshcema.mytable2 WHERE field_in_tab2 = field_in_tab1)
10) Explain plan
OPERATION - OBJECT_NAME - OPTIONS - COST
SELECT STATEMENT - - REMOTE - 3
-> NESTED LOOPS - - SEMI - 3
-> -> INDEX - MY_UK_NAME - RANGE SCAN - 3
-> -> INDEX - MY_2ND_UK - UNIQUE SCAN - 0
And the results are instantaneous
Now my question: Can somebody direct me on whether a hint or something else will correct this situation? Due to restrictions that I cannot currently explain here, I am not able to change the code to first get the value and then execute the query.
Thanks for helping
G
Edited by: G on May 17, 2011 9:07 AM
Edited by: G on May 17, 2011 9:10 AM

Answer 1

I would think the driving site hint woud be the frist thing I tried. If for some reason Oracle does not seem to be able to use the hint or if hints are heavily frowned on at your site then here is another approach to the problem.
Code the query into a view and define the view on the remote database then issues a local query against the remote view.
HTH -- Mark D Powell --