Enum Field.Index

Specifies whether and how a field should be indexed.

[Obsolete("This is here only to ease transition from the pre-4.0 APIs.")]
public enum Index

Name	Description
ANALYZED	Index the tokens produced by running the field's value through an Analyzer. This is useful for common text.
ANALYZED_NO_NORMS	Expert: Index the tokens produced by running the field's value through an Analyzer, and also separately disable the storing of norms. See NOT_ANALYZED_NO_NORMS for what norms are and why you may want to disable them.
NO	Do not index the field value. This field can thus not be searched, but one can still access its contents provided it is Field.Store.
NOT_ANALYZED	Index the field's value without using an Analyzer, so it can be searched. As no analyzer is used the value will be stored as a single term. This is useful for unique Ids like product numbers.
NOT_ANALYZED_NO_NORMS	Expert: Index the field's value without an Analyzer, and also disable the storing of norms. Note that you can also separately enable/disable norms by setting OmitNorms. No norms means that index-time field and document boosting and field length normalization are disabled. The benefit is less memory usage as norms take up one byte of RAM per indexed field for every document in the index, during searching. Note that once you index a given field with norms enabled, disabling norms will have no effect. In other words, for this to have the above described effect on a field, all instances of that field must be indexed with NOT_ANALYZED_NO_NORMS from the beginning.