Kinds of Indexes

Attribute Equality Index

An equality index is a type of index that is used to identify efficiently which entries are exactly equal to a given assertion value. An equality index may only be maintained for attributes that have a corresponding equality matching rule. That matching rule will be used to normalize values to use as index keys, and the value for that key will be the ID list containing the entry ID of the entries with values that are equal to that normalized value.

Attribute Presence Index

A presence index is a type of index that is used to keep track of the entries that have at least one value for a specified attribute. There is only a single presence index key per attribute, and its ID list contains the entry IDs for all entries that contain the specified attribute.

Attribute Substring Index

A substring index is a type of index that is used to keep track of which entries contain specific substrings. Index keys for a substring index consist of six-character substrings taken from attribute values and the corresponding values are a list containing the entry ID of the entries containing those substrings. The attribute's substring matching rule is used to normalize the values for the index keys, and substring indexes cannot be defined for attributes that do not contain substring matching rules.

Attribute Ordering Index

An ordering index is a type of index that is used to keep track of the relative order of values for an attribute. It is similar to an equality index except that it uses an ordering matching rule instead of an equality matching rule to normalized value the values. Ordering indexes may not be maintained for attributes that do not have a corresponding ordering matching rule.