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SPARSEINDEX

The SPARSEINDEX option controls the type of index algorithm that composites use to load and access their values. The value of SPARSEINDEX at the time a named composite is defined, or an unnamed composite is created, determines the type of algorithm the composite uses by default. See "Overriding the Default".

Choosing an index algorithm is important only in regard to performance issues. Any recommendations are for the version of Oracle OLAP that is associated with this documentation. You can test how using different algorithms affect performance by using the CHGDFN command to change the algorithm for a composite (for example, before loading data).

Data type

TEXT

Syntax

SPARSEINDEX = {'BTREE'|'HASH'}

Arguments

BTREE

HASH

Specifies the index algorithm that Oracle OLAP uses to load and access the values of new composites that are defined or created. BTREE is the default algorithm.

Notes

When to Use BTREE

BTREE is a standard indexing method that is recommended for composites. Use BTREE as the default unless you are an advanced user and have a special need that requires HASH. BTREE tends to group similar values together, which results in better locality of access.

When to Use HASH

HASH is a standard indexing method that should only be used when a composite has only two or three base dimensions. HASH is generally not recommended for composites. Using HASH results in a very large index table, which can be too large to fit into memory.

Overriding the Default

When you define a named composite, you can specify either BTREE or HASH as its index algorithm. When you specify an index algorithm in the DEFINE COMPOSITEcommand, this overrides the default specified by the SPARSEINDEX option. After you have defined a composite, you can also use the CHGDFN command to change the composite's index algorithm to either BTREE or HASH.

NOHASH Unavailable

A composite cannot use the NOHASH index algorithm for loading and accessing its values.

Examples

Example 21-45 Using the HASH Algorithm

The following example sets SPARSEINDEX to HASH so that composites that are subsequently defined or created will use the HASH index algorithm by default.

SPARSEINDEX = 'HASH'