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Bitmap Index

Use

While a normal index is based on a B-tree structure, a “bitmap index” uses a set of bitmaps to locate column entries. If defined on a column or columns with low cardinality, the bitmap index typically consumes less storage space and can strongly outperform a normal index in selections that use equality operators, and in combination with other bitmap indexes.

Description

The parameter type of an index describes the type of the index. The possible values are normal and bitmap. By default, the index type is normal.

Type bitmap is not allowed if the index is unique.

The type parameter can be used at most once within the Oracle scope of the index database-specific parameters.

Syntax

The index type is specified by the XML tag <type>.

Syntax Syntax

  1. <index name="myIndex">
	<is-unique>true</is-unique>
	<dbspecifics>
		<ora>
			<type>normal</type>
		</ora>
	</dbspecifics>
</index>
End of the code.