FT.SEARCH

Syntax

  1. FT.SEARCH index query
  2.   [NOCONTENT]
  3.   [RETURN count identifier [AS property] [ identifier [AS property] ...]]
  4.   [SORTBY sortby [ ASC | DESC] [WITHCOUNT]]
  5.   [LIMIT offset num]
  6.   [PARAMS nargs name value [ name value ...]]

Time complexity: O(N)

Important: New in Dragonfly v1.13. Currently, Dragonfly Search is in Beta.

Description

Search the index with a textual query, returning either documents or just IDs. For usage, see examples below.

Required arguments

index

is index name. You must first create the index using FT.CREATE.

query

is text query to search. If it’s more than a single word, put it in quotes. Refer to query syntax for more details.

Optional arguments

NOCONTENT

returns the document IDs and not the content.

This is useful if Dragonfly is storing an index on an external document collection.

RETURN num identifier AS property ...

limits the attributes returned from the document.

num is the number of attributes following the keyword. If num is 0, it acts like NOCONTENT. identifier is either an attribute name (for Hash and JSON) or a JSONPath expression (for JSON). property is an optional name used in the result. If not provided, the identifier is used in the result.

SORTBY attribute [ASC|DESC]

orders the results by the value of this attribute.

This applies to both text and numeric attributes. Attributes needed for SORTBY should be declared as SORTABLE in the index in order to be available with very low latency. Note that this adds memory overhead.

FT.SEARCH - 图1About SORTBY

The attribute used in SORTBY must be declared as SORTABLE in the index upon creation.

LIMIT first num

limits the results to the offset and number of results given.

Note that the offset is zero-indexed. The default is 0 10, which returns 10 items starting from the first result. You can use LIMIT 0 0 to count the number of documents in the result set without actually returning them.

PARAMS nargs name value

defines one or more value parameters. Each parameter has a name and a value.

You can reference parameters in the query by a $, followed by the parameter name, for example, $user. Each such reference in the search query to a parameter name is substituted by the corresponding parameter value. For example, with parameter definition PARAMS 4 start 2020 end 2021, the expression @published_at:[$start $end] is evaluated to @published_at:[2020 2021]. You cannot reference parameters in the query string where concrete values are not allowed, such as in field names, for example, @published_at.

Return

FT.SEARCH returns an array reply, where the first element is an integer reply of the total number of results, and then array reply pairs of document IDs, and array replies of attribute/value pairs.

FT.SEARCH - 图2Notes

  • If NOCONTENT is given, an array is returned where the first element is the total number of results, and the rest of the members are document IDs.
  • If a hash expires after the query process starts, the hash is counted in the total number of results, but the key name and content return as null.

Complexity

FT.SEARCH complexity is O(N) for single word queries, where N is the number of the results in the result set. Finding all the documents that have a specific term is O(1). However, a scan on all those documents is needed to load the documents data from Hash or JSON values and return them.

The time complexity for more complex queries varies, but in general it’s proportional to the number of words, the number of intersection points between them and the number of results in the result set.

Examples

Search for a term in every text attribute

Search for the term wizard in every TEXT attribute of an index containing book data.

  1. dragonfly> FT.SEARCH books-idx "wizard"
  2. ``` **Search for a term in one attribute**
  4. Search for the term `dogs` in the `title` attribute.

dragonfly> FT.SEARCH books-idx “@title:dogs” ``` Search for books from specific years

Search for books published in 2020 or 2021.

  1. dragonfly> FT.SEARCH books-idx "@published_at:[2020 2021]"
  2. ``` **Search for a book by a term and tag**
  4. Search for books with `space` in the `title` attribute that also have `science` in the `TAG` attribute `categories`.

dragonfly> FT.SEARCH books-idx “@title:space @categories:{science}” ``` Search for a book by a term but limit the number

Search for books with python in any TEXT attribute, returning 10 results starting with the 11th result in the entire result set (the offset parameter is zero-based), and return only the title attribute for each result.

  1. dragonfly> FT.SEARCH books-idx "python" LIMIT 10 10 RETURN 1 title
  2. ``` **Search for a book by a term and price**
  4. Search for books with `python` in any `TEXT` attribute, returning the `price` attributed stored in the original document.

dragonfly> FT.SEARCH books-idx “python” RETURN 3 $.book.price AS price ```

See also

FT.CREATE