Bitmap Extent Index

Bitmap Extent Index

When you create a table using CREATE TABLE, by default InterSystems IRIS automatically defines a bitmap extent index for the corresponding class. The SQL MapName of the bitmap extent index is %%DDLBEIndex:

Index DDLBEIndex [ Extent, SqlName = "%%DDLBEIndex", Type = bitmap ];

This bitmap extent index is not created in any of the following circumstances:

• The table is defined as a global temporary table (CREATE TABLE GLOBAL TEMPORARY TABLE ...).

• The table defines an explicit IDKEY index.

• The table contains a defined IDENTITY column that does not have MINVAL=1.

• The $SYSTEM.SQL.Util.SetOption()Opens in a new tab method DDLDefineBitmapExtent option is set to 0 to override the default system-wide. To determine the current setting, call the $SYSTEM.SQL.CurrentSettings()Opens in a new tab method, which displays a Do classes created by a DDL CREATE TABLE statement define a bitmap extent index setting.

If, after creating a bitmap index, the CREATE BITMAPEXTENT INDEX command is run against a table where a bitmap extent index was automatically defined, the bitmap extent index previously defined is renamed to the name specified by the CREATE BITMAPEXTENT INDEX statement.

For DDL operations that automatically delete an existing bitmap extent index, refer to ALTER TABLE.

For more details, see Bitmap Extent Index.