External Fields are useful in cases where you may want to update a particular field in some documents more often than you want to update others. For example, you may have implemented a document rank based on the number of views, and you want to update the rank of all of the documents daily or hourly. Normally, you would need to update each document just to change the rank. Adding an External Field is much more efficient, because all document values for a particular field are stored in a single external file that you can update as often as you wish.
You store the values for an External Field in a file outside of the index. The file contains mappings from a key field to the field value, so instead of specifying the field in documents as they are indexed, Voyager finds values for this field in an external file.
To add an external field:
NOTES: