Sorting
Support for sorting query results
Sorting by indexed fields
As of RediSearch 0.15, you can bypass the scoring function mechanism and order search results by the value of different document attributes (fields) directly, even if the sorting field is not used by the query. For example, you can search for first name and sort by last name.
Declaring sortable fields
When creating an index with FT.CREATE
, you can declare TEXT
, TAG
, NUMERIC
, and GEO
attributes as SORTABLE
. When an attribute is sortable, you can order the results by its values with relatively low latency. When an attribute is not sortable, it can still be sorted by its values, but with increased latency. For example, in the following schema:
FT.CREATE users SCHEMA first_name TEXT last_name TEXT SORTABLE age NUMERIC SORTABLE
The fields last_name
and age
are sortable, but first_name
isn't. This means you can search by either first and/or last name, and sort by last name or age.
Note on sortable fields
In the current implementation, when declaring a sortable field, its content gets copied into a special location in the index that provides for fast access during sorting. This means that making long fields sortable is very expensive and you should be careful with it.
Normalization (UNF option)
By default, text fields get normalized and lowercased in a Unicode-safe way when stored for sorting. For example, America
and america
are considered equal in terms of sorting.
Using the UNF
(un-normalized form) argument, it is possible to disable the normalization and keep the original form of the value. Therefore, America
will come before america
.
Specifying SORTBY
If an index includes sortable fields, you can add the SORTBY
parameter to the search request (outside the query body) to order the results. This overrides the scoring function mechanism, and the two cannot be combined. If WITHSCORES
is specified together with SORTBY
, the scores returned are simply the relative position of each result in the result set.
The syntax for SORTBY
is:
SORTBY {field_name} [ASC|DESC]
-
field_name
must be a sortable field defined in the schema. -
ASC
means ascending order,DESC
means descending order. -
The default ordering is
ASC
.
Example
> FT.CREATE users SCHEMA first_name TEXT SORTABLE last_name TEXT age NUMERIC SORTABLE
# Add some users
> FT.ADD users user1 1.0 FIELDS first_name "alice" last_name "jones" age 35
> FT.ADD users user2 1.0 FIELDS first_name "bob" last_name "jones" age 36
# Searching while sorting
# Searching by last name and sorting by first name
> FT.SEARCH users "@last_name:jones" SORTBY first_name DESC
# Searching by both first and last name, and sorting by age
> FT.SEARCH users "alice jones" SORTBY age ASC