9. Advanced Option

In the previous examples, the indices were created using a PREFIX, where all the keys matching the type and prefix are indexed.

It is also possible to create an index using a filter, for example create an index with all the "Drama" movies released between 1990 and 2000 (2000 not included).

The FILTER` expression is using the aggregation filter syntax, for example for the genre and release year it will be

• •FILTER "@genre=='Drama' && @release_year>=1990 && @release_year<2000"

So when you create the index:

FT.CREATE idx:drama ON Hash PREFIX 1 "movie:" FILTER "@genre=='Drama' && @release_year>=1990 && @release_year<2000" SCHEMA title TEXT SORTABLE release_year NUMERIC SORTABLE

You can run the FT.INFO idx:drama command to look at the index definitions and statistics.

Notes

• •The PREFIX is not optional.
• •In this appliation this index is not useful since you can get the same data from the idx:movie

You can check that the data has been indexed by running the following queries that should return the same number of documents.

On idx:drama