SQL query performance difference with Index Hint in Oracle 10g

Question

Hi,
I was having a problem in SQL select query which was taking around 20 seconds to get the results. So, by hit and trail method I added Index Oracle Hint into the same query with the list of indexes of the tables and the results are retrieved with in 10 milli seconds. I am not sure to get How this is working with Indexes Hint.
The query with out Index Hint:
select /*+rule*/ FdnTab2.fdn, paramTab3.attr_name from fdnmappingtable FdnTab, fdnmappingtable FdnTab2, parametertable paramTab1 ,parametertable paramTab3  where FdnTab.id=52787 and paramTab1.id= FdnTab.id  and paramTab3.id = FdnTab.id  and paramTab3.attr_value = FdnTab2.fdn  and paramTab1.attr_name='harqUsersMax' and paramTab1.attr_value <> 'DEFAULT' and exists ( select ParamTab2.attr_name from parametertable ParamTab2, templaterelationtable TemplateTab2  where TemplateTab2.id=FdnTab.id  and ParamTab2.id=TemplateTab2.template_id  and ParamTab2.id=FdnTab2.id  and ParamTab2.attr_name=paramTab1.attr_name)  ==> EXECUTION TIME: 20 secs
The same query with Index Hint:
select /*+INDEX(fdnmappingtable[PRIMARY_KY_FDNMAPPINGTABLE],parametertable[PRIMARY_KY_PARAMETERTABLE])*/ FdnTab2.fdn, paramTab3.attr_name from fdnmappingtable FdnTab, fdnmappingtable FdnTab2, parametertable paramTab1 ,parametertable paramTab3 where FdnTab.id=52787 and paramTab1.id= FdnTab.id and paramTab3.id = FdnTab.id and paramTab3.attr_value = FdnTab2.fdn and paramTab1.attr_name='harqUsersMax' and paramTab1.attr_value <> 'DEFAULT' and exists ( select ParamTab2.attr_name from parametertable ParamTab2, templaterelationtable TemplateTab2 where TemplateTab2.id=FdnTab.id and ParamTab2.id=TemplateTab2.template_id and ParamTab2.id=FdnTab2.id and ParamTab2.attr_name=paramTab1.attr_name) ==> EXECUTION TIME: 10 milli secs
Can any one suggest what could be the real problem?
Regards,
Purushotham

Answer 1

Sorry,
The right query and the explain plan:
select /*+rule*/ FdnTab2.fdn, paramTab3.attr_name from fdnmappingtable FdnTab, fdnmappingtable FdnTab2, parametertable paramTab1 ,parametertable paramTab3  where FdnTab.id=52787 and paramTab1.id= FdnTab.id  and paramTab3.id = FdnTab.id  and paramTab3.attr_value = FdnTab2.fdn  and paramTab1.attr_name='harqUsersMax' and paramTab1.attr_value <> 'DEFAULT' and exists ( select ParamTab2.attr_name from parametertable ParamTab2, templaterelationtable TemplateTab2  where TemplateTab2.id=FdnTab.id  and ParamTab2.id=TemplateTab2.template_id  and ParamTab2.id=FdnTab2.id  and ParamTab2.attr_name=paramTab1.attr_name) 
SQL> @$ORACLE_HOME/rdbms/admin/utlxpls.sql
PLAN_TABLE_OUTPUT
Plan hash value: 651267974
| Id | Operation | Name |
| 0 | SELECT STATEMENT | |
|* 1 | FILTER | |
| 2 | NESTED LOOPS | |
| 3 | NESTED LOOPS | |
| 4 | NESTED LOOPS | |
|* 5 | INDEX UNIQUE SCAN | PRIMARY_KY_FDNMAPPINGTABLE |
PLAN_TABLE_OUTPUT
|* 6 | TABLE ACCESS BY INDEX ROWID| PARAMETERTABLE |
|* 7 | INDEX UNIQUE SCAN | PRIMARY_KY_PARAMETERTABLE |
| 8 | TABLE ACCESS BY INDEX ROWID | PARAMETERTABLE |
|* 9 | INDEX RANGE SCAN | PRIMARY_KY_PARAMETERTABLE |
| 10 | TABLE ACCESS BY INDEX ROWID | FDNMAPPINGTABLE |
|* 11 | INDEX UNIQUE SCAN | SYS_C005695 |
| 12 | NESTED LOOPS | |
|* 13 | INDEX UNIQUE SCAN | PRIMARY_KY_PARAMETERTABLE |
|* 14 | INDEX UNIQUE SCAN | PRIMARY_KEY_TRTABLE |
PLAN_TABLE_OUTPUT
Predicate Information (identified by operation id):
1 - filter( EXISTS (SELECT 0 FROM "TEMPLATERELATIONTABLE"
"TEMPLATETAB2","PARAMETERTABLE" "PARAMTAB2" WHERE
"PARAMTAB2"."ATTR_NAME"=:B1 AND "PARAMTAB2"."ID"=:B2 AND
"PARAMTAB2"."ID"="TEMPLATETAB2"."TEMPLATE_ID" AND
"TEMPLATETAB2"."ID"=:B3))
5 - access("FDNTAB"."ID"=52787)
6 - filter("PARAMTAB1"."ATTR_VALUE"<>'DEFAULT')
7 - access("PARAMTAB1"."ID"="FDNTAB"."ID" AND
PLAN_TABLE_OUTPUT
"PARAMTAB1"."ATTR_NAME"='harqUsersMax')
9 - access("PARAMTAB3"."ID"="FDNTAB"."ID")
11 - access("PARAMTAB3"."ATTR_VALUE"="FDNTAB2"."FDN")
13 - access("PARAMTAB2"."ID"=:B1 AND "PARAMTAB2"."ATTR_NAME"=:B2)
14 - access("TEMPLATETAB2"."ID"=:B1 AND
"PARAMTAB2"."ID"="TEMPLATETAB2"."TEMPLATE_ID")
Note
- rule based optimizer used (consider using cbo)
43 rows selected.
WITH INDEX HINT:
select /*+INDEX(fdnmappingtable[PRIMARY_KY_FDNMAPPINGTABLE],parametertable[PRIMARY_KY_PARAMETERTABLE])*/ FdnTab2.fdn, paramTab3.attr_name from fdnmappingtable FdnTab, fdnmappingtable FdnTab2, parametertable paramTab1 ,parametertable paramTab3 where FdnTab.id=52787 and paramTab1.id= FdnTab.id and paramTab3.id = FdnTab.id and paramTab3.attr_value = FdnTab2.fdn and paramTab1.attr_name='harqUsersMax' and paramTab1.attr_value <> 'DEFAULT' and exists ( select ParamTab2.attr_name from parametertable ParamTab2, templaterelationtable TemplateTab2 where TemplateTab2.id=FdnTab.id and ParamTab2.id=TemplateTab2.template_id and ParamTab2.id=FdnTab2.id and ParamTab2.attr_name=paramTab1.attr_name);
SQL> @$ORACLE_HOME/rdbms/admin/utlxpls.sql
PLAN_TABLE_OUTPUT
Plan hash value: 2924316070
| Id | Operation | Name | Rows | B
ytes | Cost (%CPU)| Time |
PLAN_TABLE_OUTPUT
| 0 | SELECT STATEMENT | | 1 |
916 | 6 (0)| 00:00:01 |
|* 1 | FILTER | | |
| | |
| 2 | NESTED LOOPS | | 1 |
916 | 4 (0)| 00:00:01 |
| 3 | NESTED LOOPS | | 1 |
401 | 3 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
| 4 | NESTED LOOPS | | 1 |
207 | 2 (0)| 00:00:01 |
|* 5 | TABLE ACCESS BY INDEX ROWID| PARAMETERTABLE | 1 |
194 | 1 (0)| 00:00:01 |
|* 6 | INDEX UNIQUE SCAN | PRIMARY_KY_PARAMETERTABLE | 1 |
| 1 (0)| 00:00:01 |
|* 7 | INDEX UNIQUE SCAN | PRIMARY_KY_FDNMAPPINGTABLE | 1 |
PLAN_TABLE_OUTPUT
13 | 1 (0)| 00:00:01 |
| 8 | TABLE ACCESS BY INDEX ROWID | PARAMETERTABLE | 1 |
194 | 1 (0)| 00:00:01 |
|* 9 | INDEX RANGE SCAN | PRIMARY_KY_PARAMETERTABLE | 1 |
| 1 (0)| 00:00:01 |
| 10 | TABLE ACCESS BY INDEX ROWID | FDNMAPPINGTABLE | 1 |
515 | 1 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
|* 11 | INDEX UNIQUE SCAN | SYS_C005695 | 1 |
| 1 (0)| 00:00:01 |
| 12 | NESTED LOOPS | | 1 |
91 | 2 (0)| 00:00:01 |
|* 13 | INDEX UNIQUE SCAN | PRIMARY_KEY_TRTABLE | 1 |
26 | 1 (0)| 00:00:01 |
|* 14 | INDEX UNIQUE SCAN | PRIMARY_KY_PARAMETERTABLE | 1 |
65 | 1 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
Predicate Information (identified by operation id):
1 - filter( EXISTS (SELECT /*+ */ 0 FROM "TEMPLATERELATIONTABLE" "TEMPLATETAB
2","PARAMETERTABLE"
PLAN_TABLE_OUTPUT
"PARAMTAB2" WHERE "PARAMTAB2"."ATTR_NAME"=:B1 AND "PARAMTAB2"."ID"
=:B2 AND
"TEMPLATETAB2"."TEMPLATE_ID"=:B3 AND "TEMPLATETAB2"."ID"=:B4))
5 - filter("PARAMTAB1"."ATTR_VALUE"<>'DEFAULT')
6 - access("PARAMTAB1"."ID"=52787 AND "PARAMTAB1"."ATTR_NAME"='harqUsersMax')
7 - access("FDNTAB"."ID"=52787)
9 - access("PARAMTAB3"."ID"=52787)
11 - access("PARAMTAB3"."ATTR_VALUE"="FDNTAB2"."FDN")
13 - access("TEMPLATETAB2"."ID"=:B1 AND "TEMPLATETAB2"."TEMPLATE_ID"=:B2)
14 - access("PARAMTAB2"."ID"=:B1 AND "PARAMTAB2"."ATTR_NAME"=:B2)
PLAN_TABLE_OUTPUT
Note
- dynamic sampling used for this statement
39 rows selected.