||Oracle Tips by Burleson
Monitoring Bitmap Join
As noted earlier, bitmap join indexes were
introduced in Oracle. If the JOIN_INDEX column in the DBA_INDEXES
is set to YES, then the index is a bitmap join index, meaning that a
join to the DBA_JOIN_IND_COLUMNS view will produce the data on the
tables and columns that are linked through the bitmap join index.
You will need to join against the INDEX_OWNER and INDEX_NAME
My testing, however, revealed an apparent
flaw in the DBA_JOIN_IND_COLUMNS view--at least based on how I
believe it should work. That view seems to have the same number of
columns as the DBA_IND_COLUMNS view. In addition, it contains only
one row per bitmap join index, when it should show one row for each
of the two tables involved in the bitmap join. In tests where I
created a bitmap join between two tables with different column
names, only one row was displayed. Where the actual information
about the second table is stored, if it is, is not clear. Until this
is resolved I suggest using naming conventions to clarify the
required table-to-table relationship.
See Code Depot
Copyright © 1996 - 2014 by
Burleson. All rights reserved.
Oracle® is the registered trademark
of Oracle Corporation.