Confused about cursor_sharing=force

Question

SQL> col name for a20
SQL> col type for a20
SQL> show parameter cursor_sharing
NAME TYPE
VALUE
cursor_sharing string
FORCE
SQL> drop table test;
Table dropped.
SQL> create table test(id int,name varchar2(100));
Table created.
SQL> insert into test select 1,object_name from dba_objects;
49794 rows created.
SQL> insert into test select object_id,object_name from dba_objects;
49794 rows created.
SQL> create index i_test_1 on test(id);
Index created.
SQL> analyze table test compute statistics for table for all indexes for all
2 indexed columns size 254;
Table analyzed.
SQL> set autot trace
SQL> select * from test where id=1;
49794 rows selected.
Execution Plan
Plan hash value: 1357081020
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 49402 | 1495K| 106 (4)| 00:00:02 |
|* 1 | TABLE ACCESS FULL| TEST | 49402 | 1495K| 106 (4)| 00:00:02 |
Predicate Information (identified by operation id):
1 - filter("ID"=1)
Statistics
1 recursive calls
0 db block gets
3766 consistent gets
148 physical reads
0 redo size
1489087 bytes sent via SQL*Net to client
36894 bytes received via SQL*Net from client
3321 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
49794 rows processed
SQL> select * from test where id=10000;
no rows selected
Execution Plan
Plan hash value: 3275607494
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Ti
me |
| 0 | SELECT STATEMENT | | 1 | 31 | 2 (0)| 00
:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| TEST | 1 | 31 | 2 (0)| 00
:00:01 |
|* 2 | INDEX RANGE SCAN | I_TEST_1 | 1 | | 1 (0)| 00
:00:01 |
Predicate Information (identified by operation id):
2 - access("ID"=10000)
Statistics
0 recursive calls
0 db block gets
462 consistent gets
58 physical reads
0 redo size
325 bytes sent via SQL*Net to client
374 bytes received via SQL*Net from client
1 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
0 rows processed
why not choose full table scan here?????
There are no rows returned, why still have 462 consistent gets
SQL> set autot off
SQL> select sql_text,version_count from v$sqlarea where sql_text like
2 'select * from test%';
SQL_TEXT
VERSION_COUNT
select * from test where id=:"SYS_B_0"
1
oracle version :10.2.0.1
os :windows xp
Edited by: jinyu on Aug 27, 2008 10:03 PM

Answer 1

SQL> ALTER SESSION SET NLS_LANGUAGE=AMERICAN;
Session altered.
SQL> alter system set cursor_sharing=force;
System altered.
SQL> create table test as select 1 id,object_name from dba_objects;
Table created.
SQL> insert into test select object_id,object_name from dba_objects;
49794 rows created.
SQL> commit;
Commit complete.
SQL> create index i_test_1 on test(id);
Index created.
SQL> analyze table test compute statistics for table for all indexes for all indexed columns size 25
4;
Table analyzed.
SQL> set autot trace
SQL> select * from test where id=1;
49794 rows selected.
Execution Plan
Plan hash value: 1357081020
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 49402 | 1495K| 106 (4)| 00:00:02 |
|* 1 | TABLE ACCESS FULL| TEST | 49402 | 1495K| 106 (4)| 00:00:02 |
Predicate Information (identified by operation id):
1 - filter("ID"=1)
Statistics
1 recursive calls
0 db block gets
3768 consistent gets
4 physical reads
0 redo size
1489094 bytes sent via SQL*Net to client
36894 bytes received via SQL*Net from client
3321 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
49794 rows processed
SQL> select * from test where id=10000;
no rows selected
Execution Plan
Plan hash value: 3275607494
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Ti
me |
| 0 | SELECT STATEMENT | | 1 | 31 | 2 (0)| 00
:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| TEST | 1 | 31 | 2 (0)| 00
:00:01 |
|* 2 | INDEX RANGE SCAN | I_TEST_1 | 1 | | 1 (0)| 00
:00:01 |
Predicate Information (identified by operation id):
2 - access("ID"=10000)
Statistics
0 recursive calls
0 db block gets
462 consistent gets
14 physical reads
0 redo size
332 bytes sent via SQL*Net to client
374 bytes received via SQL*Net from client
1 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
0 rows processed
SQL> select sql_text,PLAN_HASH_VALUE,version_count,executions,parse_calls
2 from v$sqlarea where sql_text like '%select * from test%';
SQL_TEXT
PLAN_HASH_VALUE VERSION_COUNT EXECUTIONS PARSE_CALLS
EXPLAIN PLAN SET STATEMENT_ID='PLUS4294967295' FOR select * from test where id=1
1357081020 1 1 1
select * from test where id=:"SYS_B_0"
1357081020 1 2 2
EXPLAIN PLAN SET STATEMENT_ID='PLUS4294967295' FOR select * from test where id=1
0000
3275607494 1 1 1
SQL_TEXT
PLAN_HASH_VALUE VERSION_COUNT EXECUTIONS PARSE_CALLS
--------------- ------------- ---------- -----------