BITMAP CONVERSION (COUNT) Operation

Description

Returns count of number of rows in one or more bitmap

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);

The table does not need to be analysed. NOT NULL constraints are not required for the indexed column(s) as bitmap indexes include a bitmap for NULL values

The statement

    SELECT /*+ INDEX (t1 i1) */ COUNT(*) FROM t1;

generates the following execution plan

0     SELECT STATEMENT Optimizer=CHOOSE
1   0   SORT (AGGREGATE)
2   1     BITMAP CONVERSION (COUNT)
3   2       BITMAP INDEX (FULL SCAN) OF 'I1'