Hello Listers,
A normal sql query from a data warehouse tool called Sagent.
SELECT COL1, COL2, COL3
FROM TABLE
ORDER BY 3;
The table has approximately 2 mil records.
table has 22 indexes.
The database is set up optimizer CHOOSE.
I run DBMS_Stats.Gather_Schema_Stats('SchemaName') regularly.
OS is Win2k
ORACLE 81741
OK, when doing a explain plan on the above sql, I get the following...
SELECT STATEMENT Optimizer Mode=CHOOSE
SORT ORDER BY
TABLE ACCESS FULL TABLENAME -- Very slow and takes
hours!
When adding the hint /*+RULE*/ for example I get
SELECT STATEMENT Optimizer Mode=Hint:RULE
TABLE ACCESS BY INDEX ROWID TABLENAME
INDEX FULL SCAN TABLE_INDEX --
Much faster!!!
Have I given enough info that anyone can explain why the CHOOSE mode insists
on doing a TABLE ACCESS FULL?
Is there anything I can do to improve performance? Please remember that this
query comes from a Data Warehouse tool and hence does not appear to accept
hints.
Any help will be much appreciated!
Denham
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Author: Denham Eva
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