Topic: Backup & Recovery >> Plan hash value
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| Ajith |
Posted: Mar 10, 2008 09:26:08 AM |
Total Post: 4
Joined: Jan, 2008
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All,
Could somebody explain me whether the hash values differ during execution of the same SQL with diffrent variables and during the execution with a bind var.
Thanks in advance
Ajith |
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 Vinod |
| Posted: Mar 10, 2008 10:24:36 AM |  |
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Total Post: 54
Joined: Oct, 2007
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Ajith,
Have a look on the simple demo listed below ,
SQL> create table test (
2 col1 number
3 )
4 /
Table created.
SQL> declare
begin
for i in 1..10000
loop
insert into TEST values(i);
end loop;
end;
/
PL/SQL procedure successfully completed.
SQL> select count(*) from test;
COUNT(*)
----------
10000
SQL> create index test_idx on test(col1);
Index created.
SQL> begin
dbms_stats.gather_table_stats
( user, 'TEST',
method_opt=> 'for all indexed columns size 254' );
end;
/
PL/SQL procedure successfully completed.
SQL> set autotrace traceonly explain
SQL> select * from test where col1 =10;
Execution Plan
----------------------------------------------------------
Plan hash value: 2882402178
-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 3 | 1 (0)| 00:00:01 |
|* 1 | INDEX RANGE SCAN| TEST_IDX | 1 | 3 | 1 (0)| 00:00:01 |
-----------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("COL1"=10)
SQL> select * from test where col1 =100;
Execution Plan
----------------------------------------------------------
Plan hash value: 2882402178
-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 3 | 1 (0)| 00:00:01 |
|* 1 | INDEX RANGE SCAN| TEST_IDX | 1 | 3 | 1 (0)| 00:00:01 |
-----------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("COL1"=100)
will have a look on the same using bind variable,
SQL> set autotrace on
SQL> conn test/test
Connected.
SQL> set autotrace on
SQL> variable col1 number
SQL> exec :col1 :=101
PL/SQL procedure successfully completed.
SQL> select * from test where col1=:col1;
COL1
----------
101
Execution Plan
----------------------------------------------------------
Plan hash value: 2882402178
-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 3 | 1 (0)| 00:00:01 |
|* 1 | INDEX RANGE SCAN| TEST_IDX | 1 | 3 | 1 (0)| 00:00:01 |
-----------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("COL1"=TO_NUMBER(:COL1))
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