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superseded by Metamorph Inverted index compound fields.
