The BITMAP JOIN INDEX UPDATE operation updates a bitmap join index after statement execution.
The BITMAP JOIN INDEX UPDATE STATEMENT operation updates a bitmap index after statement execution as seen in V$SQL_PLAN view.
Execution Plan image:
Row operation.
The BITMAP KEY ITERATION operation returns multiple values from a bitmap index.
Execution Plan image:
Row operation.
The BITMAP MERGE operation merges two or more bitmaps from the same index.
Assume that both City and State columns each has a single-column bitmap index.
select Name, City, State
from COMPANY
where City like 'New*'
or State in ('NY','NJ','CT');
This query selects rows from the COMPANY for all the companies in cities that begin with 'New' or in the states "NY", "NJ", "CT."
TABLE ACCESS (BY INDEX ROWID) OF 'COMPANY'
BITMAP CONVERSION (TO ROWIDS)
BITMAP AND
BITMAP OR
BITMAP INDEX (SINGLE VALUE) OF 'COMPANY$STATE'
BITMAP INDEX (SINGLE VALUE) OF 'COMPANY$STATE'
BITMAP INDEX (SINGLE VALUE) OF 'COMPANY$STATE'
BITMAP MERGE
BITMAP INDEX (RANGE SCAN) OF 'COMPANY$CITY'
The plan shows that the bitmap index on the State column is used to find a bitmap for all the rows in the COMPANY table that satisfy the where clause condition (where State in ('NY', 'NJ', 'CT')). The index is accessed three times—once per state. A BITMAP OR operation creates one bitmap from all the individual state bitmaps. The index on the City column is then accessed to find all the cities that begin with 'New'. The BITMAP MERGE operation merges all the individual bitmaps from every city that starts with 'New' into one bitmap. The new City bitmap and the new State bitmap are then merged into the final bitmap using a BITMAP AND operation. The final bitmap is converted to the ROWID list to access the table.
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