Thunderstone Search Appliance Manual

Index Types

There are several types of indexes that can be created by the Texis SQL engine - the underlying technology that powers the Parametric Search Appliance. Each is best suited to different types of queries.

• Metamorph Inverted A Metamorph Inverted index handles text searches; the main text search uses one for example. It is often created on several fields that are searched together as one (e.g. Title, Meta, Body) - called a virtual field. A Metamorph Inverted index can also handle some secondary queries on separate fields that are ANDed after the text search - called compound fields.

• Metamorph A Metamorph index is a smaller version of a Metamorph Inverted index. It is of benefit when text searches are to be done, but no phrases will be searched for, nor is relevance ranking needed. In these situations the smaller size of a Metamorph index may improve search speed.

• Regular A Regular index handles relational operators (equals, greater-than, less-than etc.), as well as order-by queries. It is usually created on one field, but can be created on several (i.e. compound fields).

• Unique A Unique index is the same as a Regular index, except that it enforces uniqueness across its fields: no document may be added that has the same value (for all fields in the index) as an existing document.

• Inverted An Inverted index speeds up access to its indexed values if they are ANDed after another query. Its use is largely superseded by Metamorph Inverted index compound fields.