Source: https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/fe/functions/fulltext/
Documentation version: v5.3.2

# Full-text index functions

Use the following GQL functions with full-text indexes.

To use these functions, you need to create a full-text index first. For more information, see [CREATE FULLTEXT INDEX](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/ddl/index/create-fulltext/).

## ftscore()

Returns the score of [BM25](https://en.wikipedia.org/wiki/Okapi_BM25) relevance between a `STRING` value stored by an indexed property and a given query string.

The score is a non-negative floating-point number in the range `[0, +∞)`. A higher score indicates greater relevance to the query string.

Null behavior: error

This function must be used together with one of the following clauses:

- A [WHERE clause](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/dql/clauses/where/) that filters results by score (for example, `score > 0`).
- A [LIMIT clause](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/dql/clauses/limit/) that limits the number of results returned.

For more information, see the Examples below.

### Function signature

````
ftscore(property_value_expression String, query String) -> DOUBLE

````

- `property_value_expression`: The [property value expression](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/fe/expressions/property/) that references a `STRING` property of a node type or edge type. A full-text index must already be created on this property.
- `query`: The query string against which the property value is compared to calculate the relevance score.

### Examples

The following examples assume the full-text index `ft_movie` introduced in [CREATE FULLTEXT INDEX](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/ddl/index/create-fulltext/) is already created.

#### Filter by relevance score

````
'''
USE movie 
MATCH (v@Movie) 
LET score= ftscore(v.name, 'Uncle') 
FILTER WHERE score > 0 
RETURN v.name AS movie_name, score 
'''

````

Return:

````
+------------+--------------------+
| movie_name | score              |
+------------+--------------------+
| My Uncle   | 3.1877928754939955 |
+------------+--------------------+

````

#### Limit the number of results returned

````
'''
USE movie 
MATCH (v@Movie) 
LET score= ftscore(v.name, 'Star') 
RETURN v.name AS movie_name, score 
ORDER BY score ASC 
LIMIT 3
'''

````

Return:

````
+-------------------------------------+--------------------+
| movie_name                          | score              |
+-------------------------------------+--------------------+
| Star Trek III: The Search for Spock | 1.1281776534864079 |
| Star Trek: The Motion Picture       | 1.2483069947936236 |
| Star Trek: Generations              | 1.4253784613321967 |
+-------------------------------------+--------------------+

````