Text Search in the Aggregation Pipeline
In the aggregation pipeline, text search is available via the use of
the $text
query operator in the $match
stage.
Restrictions
For general $text
operator restrictions, see operator
restrictions.
In addition, text search in the aggregation pipeline has the following restrictions:
The
$match
stage that includes a$text
must be the first stage in the pipeline.A
$text
operator can only occur once in the stage.The
$text
operator expression cannot appear in$or
or$not
expressions.The text search, by default, does not return the matching documents in order of matching scores. To sort by descending score, use the
$meta
aggregation expression in the$sort
stage.
Text Score
The $text
operator assigns a score to each document that
contains the search term in the indexed fields. The score represents
the relevance of a document to a given text search query. The score can
be part of a $sort
pipeline specification as well as part of the
projection expression. The { $meta: "textScore" }
expression
provides information on the processing of the $text
operation.
See $meta
for details on accessing the score for
projection or sort.
The metadata is only available after the $match
stage that
includes the $text
operation.
Examples
The following examples assume a collection articles
that has a text
index on the field subject
:
db.articles.createIndex( { subject: "text" } )
Calculate the Total Views for Articles that Contains a Word
The following aggregation searches for the term cake
in the
$match
stage and calculates the total views
for the
matching documents in the $group
stage.
db.articles.aggregate( [ { $match: { $text: { $search: "cake" } } }, { $group: { _id: null, views: { $sum: "$views" } } } ] )
Return Results Sorted by Text Search Score
To sort by the text search score, include a {$meta:
"textScore"}
expression in the $sort
stage. The
following example matches on either the term cake
or tea
,
sorts by the textScore
in descending order, and returns only the
title
field in the results set.
db.articles.aggregate( [ { $match: { $text: { $search: "cake tea" } } }, { $sort: { score: { $meta: "textScore" } } }, { $project: { title: 1, _id: 0 } } ] )
The specified metadata determines the sort order. For example, the
"textScore"
metadata sorts in descending order. See
$meta
for more information on metadata as well as an
example of overriding the default sort order of the metadata.
Match on Text Score
The "textScore"
metadata is available for projections, sorts, and
conditions subsequent the $match
stage that includes the
$text
operation.
The following example matches on either the term cake
or tea
,
projects the title
and the score
fields, and then returns only
those documents with a score
greater than 1.0
.
db.articles.aggregate( [ { $match: { $text: { $search: "cake tea" } } }, { $project: { title: 1, _id: 0, score: { $meta: "textScore" } } }, { $match: { score: { $gt: 1.0 } } } ] )
Specify a Language for Text Search
The following aggregation searches in spanish for documents that
contain the term saber
but not the term claro
in the
$match
stage and calculates the total views
for the
matching documents in the $group
stage.
db.articles.aggregate( [ { $match: { $text: { $search: "saber -claro", $language: "es" } } }, { $group: { _id: null, views: { $sum: "$views" } } } ] )
$search
Stage in Atlas Search
For data hosted on MongoDB Atlas, Atlas Search provides the $search aggregation stage to perform full-text search on your collections.