text: **Important:**Folder queries that use filter fields alone result in a sequential scan through 
  database tables. An index field must always be included in folder queries. For more 
  information about folders, see 3.1.4, “Folders” on page 54. 
  
  A thorough understanding of the way that users search for documents in the system is 
  required before you determine the fields that will be indexes and the fields that will be filters. 
  Only fields that will be heavily used when users are searching for and retrieving documents 
  need a type of index. An index field will always be included in a folder query. 
  
  **Note:**Date fields are almost always defined as filters, not indexes. 
  
  **Segment**
  *Segment*is the date or date and time field that is used to limit the number of tables that are 
  searched during a folder query. By using a segment date to limit folder queries to a single 
  table or a limited set of tables, performance is improved. The segment date is especially 
  important for application groups that contain a large amount of data. 
  
  If the expiration type is segment, Content Manager OnDemand also uses the segment field to 
  determine when to delete data from the application group. You might specify only one 
  segment field for each application group. 