1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59
| create table t
(
a number,
b number
);
insert into t (a, b) values (1, 2);
insert into t (a, b) values (3, 1);
insert into t (a, b) values (4, 2);
commit;
BEGIN
DBMS_STATS.GATHER_TABLE_STATS
(
OWNNAME => user,
TABNAME => 'T',
ESTIMATE_PERCENT => 100,
CASCADE => TRUE
);
END;
/
select * from t
where a + b - 1 = 5;
/*
Plan
SELECT STATEMENT ALL_ROWSCost: 4 Bytes: 6 Cardinality: 1
1 TABLE ACCESS FULL TABLE T Cost: 4 Bytes: 6 Cardinality: 1
*/
create index i
on t (a + b - 1);
BEGIN
DBMS_STATS.GATHER_TABLE_STATS
(
OWNNAME => user,
TABNAME => 'T',
ESTIMATE_PERCENT => 100,
CASCADE => TRUE
);
END;
/
select * from t
where a + b - 1 = 5;
/*
Plan
SELECT STATEMENT ALL_ROWSCost: 2 Bytes: 9 Cardinality: 1
2 TABLE ACCESS BY INDEX ROWID TABLE T Cost: 2 Bytes: 9 Cardinality: 1
1 INDEX RANGE SCAN INDEX I Cost: 1 Cardinality: 1
*/
drop index i;
drop table t; |
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