BITMAP OR

Description

Selects rows from a table based on the result of applying an OR on two bitmap indexes

Versions

This operation is implemented in the following versions

Example

This example was developed using Oracle 9.2.0.1 on Windows 2000

This example requires the following table and index definitions

    CREATE TABLE t1 (c1 NUMBER,c2 NUMBER);

    CREATE BITMAP INDEX i1 ON t1 (c1);
    CREATE BITMAP INDEX i2 ON t1 (c2);

The table does not need to be analysed

The statement

    SELECT /*+ INDEX_COMBINE (t1 i1 i2) */ c1,c2
    FROM t1
    WHERE c1 = 0 OR c2 = 0;

generates the following execution plan

   0      SELECT STATEMENT Optimizer=CHOOSE 
   1    0   TABLE ACCESS (BY INDEX ROWID) OF 'T1' 
   2    1     BITMAP CONVERSION (TO ROWIDS)
   3    2       BITMAP OR
   4    3         BITMAP INDEX (SINGLE VALUE) OF 'I1'
   5    3         BITMAP INDEX (SINGLE VALUE) OF 'I2'