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Control Search Results with Weights
Text search assigns a score to each document that contains the search term in the indexed fields. The score determines the relevance of a document to a given search query.
For a text
index, the weight of an indexed field denotes the
significance of the field relative to the other indexed fields in terms
of the text search score.
For each indexed field in the document, MongoDB multiplies the number
of matches by the weight and sums the results. Using this sum, MongoDB
then calculates the score for the document. See $meta
operator for details on returning and sorting by text scores.
The default weight is 1 for the indexed fields. To adjust the weights
for the indexed fields, include the weights
option in the
db.collection.createIndex()
method.
Warning
Choose the weights carefully in order to prevent the need to reindex.
A collection blog
has the following documents:
{ _id: 1, content: "This morning I had a cup of coffee.", about: "beverage", keywords: [ "coffee" ] } { _id: 2, content: "Who doesn't like cake?", about: "food", keywords: [ "cake", "food", "dessert" ] }
To create a text
index with different field weights for the
content
field and the keywords
field, include the weights
option to the createIndex()
method. For
example, the following command creates an index on three fields and
assigns weights to two of the fields:
db.blog.createIndex( { content: "text", keywords: "text", about: "text" }, { weights: { content: 10, keywords: 5 }, name: "TextIndex" } )
The text
index has the following fields and weights:
content
has a weight of 10,keywords
has a weight of 5, andabout
has the default weight of 1.
These weights denote the relative significance of the indexed fields to
each other. For instance, a term match in the content
field has:
2
times (i.e.10:5
) the impact as a term match in thekeywords
field and10
times (i.e.10:1
) the impact as a term match in theabout
field.
Note
For data hosted on MongoDB Atlas,
Atlas Search provides more robust custom
scoring than text
indexes. To learn more, see the Atlas Search
Scoring documentation.