$text¶
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Definition¶
-
$text¶ $textperforms a text search on the content of the fields indexed with a text index. A$textexpression has the following syntax:Changed in version 3.2.
The
$textoperator accepts a text query document with the following fields:Field Type Description $searchstring A string of terms that MongoDB parses and uses to query the text index. MongoDB performs a logical ORsearch of the terms unless specified as a phrase. See Behavior for more information on the field.$languagestring Optional. The language that determines the list of stop words for the search and the rules for the stemmer and tokenizer. If not specified, the search uses the default language of the index. For supported languages, see Text Search Languages.
If you specify a language value of
"none", then the text search uses simple tokenization with no list of stop words and no stemming.$caseSensitiveboolean Optional. A boolean flag to enable or disable case sensitive search. Defaults to
false; i.e. the search defers to the case insensitivity of the text index.For more information, see Case Insensitivity.
New in version 3.2.
$diacriticSensitiveboolean Optional. A boolean flag to enable or disable diacritic sensitive search against version 3 text indexes. Defaults to
false; i.e. the search defers to the diacritic insensitivity of the text index.Text searches against earlier versions of the text index are inherently diacritic sensitive and cannot be diacritic insensitive. As such, the
$diacriticSensitiveoption has no effect with earlier versions of the text index.For more information, see Diacritic Insensitivity.
New in version 3.2.
The
$textoperator, by default, does not return results sorted in terms of the results’ scores. For more information on sorting by the text search scores, see the Text Score documentation.
Behavior¶
Restrictions¶
- A query can specify, at most, one
$textexpression. - The
$textquery can not appear in$norexpressions. - The
$textquery can not appear in$elemMatchquery expressions or$elemMatchprojection expressions. - To use a
$textquery in an$orexpression, all clauses in the$orarray must be indexed. - You cannot use
hint()if the query includes a$textquery expression. - You cannot specify
$naturalsort order if the query includes a$textexpression. - You cannot combine the
$textexpression, which requires a special text index, with a query operator that requires a different type of special index. For example you cannot combine$textexpression with the$nearoperator. - Views do not support text search.
If using the $text operator in aggregation, the following
restrictions also apply.
- The
$matchstage that includes a$textmust be the first stage in the pipeline. - A
textoperator can only occur once in the stage. - The
textoperator expression cannot appear in$oror$notexpressions. - The text search, by default, does not return the matching documents
in order of matching scores. Use the
$metaaggregation expression in the$sortstage.
$search Field¶
In the $search field, specify a string of words that the
text operator parses and uses to query the text index.
The text operator treats most punctuation
in the string as delimiters, except a hyphen-minus (-) that negates term or
an escaped double quotes \" that specifies a phrase.
Phrases¶
To match on a phrase, as opposed to individual terms, enclose the
phrase in escaped double quotes (\"), as in:
If the $search string includes a phrase and individual terms, text
search will only match the documents that include the phrase.
For example, passed a $search string:
The $text operator searches for the phrase "ssl
certificate".
Negations¶
Prefixing a word with a hyphen-minus (-) negates a word:
- The negated word excludes documents that contain the negated word from the result set.
- When passed a search string that only contains negated words, text search will not match any documents.
- A hyphenated word, such as
pre-market, is not a negation. If used in a hyphenated word,$textoperator treats the hyphen-minus (-) as a delimiter. To negate the wordmarketin this instance, include a space betweenpreand-market, i.e.,pre -market.
The $text operator adds all negations to the query with the
logical AND operator.
Match Operation¶
Stop Words¶
The $text operator ignores language-specific stop words, such
as the and and in English.
Stemmed Words¶
For case insensitive and diacritic insensitive text searches, the
$text operator matches on the complete stemmed word. So if a
document field contains the word blueberry, a search on the term
blue will not match. However, blueberry or blueberries will
match.
Case Sensitive Search and Stemmed Words¶
For case sensitive search (i.e.
$caseSensitive: true), if the suffix stem contains uppercase
letters, the $text operator matches on the exact word.
Diacritic Sensitive Search and Stemmed Words¶
For diacritic sensitive
search (i.e. $diacriticSensitive: true), if the suffix stem
contains the diacritic mark or marks, the $text operator
matches on the exact word.
Case Insensitivity¶
Changed in version 3.2.
The $text operator defaults to the case insensitivity of the
text index:
- The version 3 text index is case insensitive for Latin characters with or without diacritics and characters from non-Latin alphabets, such as the Cyrillic alphabet. See text index for details.
- Earlier versions of the
textindex are case insensitive for Latin characters without diacritic marks; i.e. for[A-z].
$caseSensitive Option¶
To support case sensitive search where the text index is case
insensitive, specify $caseSensitive: true.
Case Sensitive Search Process¶
When performing a case sensitive search ($caseSensitive: true)
where the text index is case insensitive, the $text
operator:
- First searches the
textindex for case insensitive and diacritic matches. - Then, to return just the documents that match the case of the search
terms, the
$textquery operation includes an additional stage to filter out the documents that do not match the specified case.
For case sensitive search (i.e. $caseSensitive: true), if
the suffix stem contains uppercase letters, the $text operator
matches on the exact word.
Specifying $caseSensitive: true may impact performance.
See also
Diacritic Insensitivity¶
Changed in version 3.2.
The $text operator defaults to the diacritic insensitivity of
the text index:
- The version 3 text index is
diacritic insensitive. That is, the index does not distinguish
between characters that contain diacritical marks and their
non-marked counterpart, such as
é,ê, ande. - Earlier versions of the
textindex are diacritic sensitive.
$diacriticSensitive Option¶
To support diacritic sensitive text search against the version 3
text index, specify $diacriticSensitive: true.
Text searches against earlier versions of the text index are
inherently diacritic sensitive and cannot be diacritic insensitive. As
such, the $diacriticSensitive option for the $text
operator has no effect with earlier versions of the text index.
Diacritic Sensitive Search Process¶
To perform a diacritic sensitive text search ($diacriticSensitive:
true) against a version 3 text index, the $text operator:
- First searches the
textindex, which is diacritic insensitive. - Then, to return just the documents that match the diacritic marked
characters of the search terms, the
$textquery operation includes an additional stage to filter out the documents that do not match.
Specifying $diacriticSensitive: true may impact performance.
To perform a diacritic sensitive search against an earlier version of
the text index, the $text operator searches the text
index which is diacritic sensitive.
For diacritic sensitive search, if the suffix stem contains the
diacritic mark or marks, the $text operator matches on the
exact word.
See also
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() method specification as well as part of the
projection expression. The { $meta: "textScore" } expression
provides information on the processing of the $text operation.
See $meta projection operator for details on accessing the score for
projection or sort.
Examples¶
The following examples assume a collection articles that has a
version 3 text index on the field subject:
Populate the collection with the following documents:
Search for a Single Word¶
The following query specifies a $search string of coffee:
This query returns the documents that contain the term coffee in the
indexed subject field, or more precisely, the stemmed version of
the word:
See also
Match Any of the Search Terms¶
If the search string is a space-delimited string, $text
operator performs a logical OR search on each term and returns
documents that contains any of the terms.
The following query specifies a $search string of three terms
delimited by space, "bake coffee cake":
This query returns documents that contain either bake or
coffee or cake in the indexed subject field, or more
precisely, the stemmed version of these words:
See also
Search for a Phrase¶
To match the exact phrase as a single term, escape the quotes.
The following query searches for the phrase coffee shop:
This query returns documents that contain the phrase coffee shop:
See also
Exclude Documents That Contain a Term¶
A negated term is a term that is prefixed by a minus sign -. If
you negate a term, the $text operator will exclude the
documents that contain those terms from the results.
The following example searches for documents that contain the words
coffee but do not contain the term shop, or more precisely
the stemmed version of the words:
The query returns the following documents:
See also
Search a Different Language¶
Use the optional $language field in the $text expression
to specify a language that determines the list of stop words and the
rules for the stemmer and tokenizer for the search string.
If you specify a language value of "none", then the text search
uses simple tokenization with no list of stop words and no stemming.
The following query specifies es, i.e. Spanish, as the language
that determines the tokenization, stemming, and stop words:
The query returns the following documents:
The $text expression can also accept the language by name,
spanish. See Text Search Languages for the supported
languages.
See also
Case and Diacritic Insensitive Search¶
Changed in version 3.2.
The $text operator defers to the case and diacritic
insensitivity of the text index. The version 3 text index is
diacritic insensitive and expands its case insensitivity to include the
Cyrillic alphabet as well as characters with diacritics. For details,
see text Index Case Insensitivity and text Index Diacritic
Insensitivity.
The following query performs a case and diacritic insensitive text
search for the terms сы́рники or CAFÉS:
Using the version 3 text index, the query matches the following
documents.
With the previous versions of the text index, the query would not
match any document.
Perform Case Sensitive Search¶
Changed in version 3.2.
To enable case sensitive search, specify $caseSensitive: true.
Specifying $caseSensitive: true may impact performance.
Case Sensitive Search for a Term¶
The following query performs a case sensitive search for the term
Coffee:
The search matches just the document:
Case Sensitive Search for a Phrase¶
The following query performs a case sensitive search for the phrase
Café Con Leche:
The search matches just the document:
Case Sensitivity with Negated Term¶
A negated term is a term that is prefixed by a minus sign -. If
you negate a term, the $text operator will exclude the
documents that contain those terms from the results. You can also
specify case sensitivity for negated terms.
The following example performs a case sensitive search for documents
that contain the word Coffee but do not contain the lower-case
term shop, or more precisely the stemmed version of the words:
The query matches the following document:
Diacritic Sensitive Search¶
Changed in version 3.2.
To enable diacritic sensitive search against a version 3 text index, specify $diacriticSensitive: true.
Specifying $diacriticSensitive: true may impact performance.
Diacritic Sensitive Search for a Term¶
The following query performs a diacritic sensitive text search on the
term CAFÉ, or more precisely the stemmed version of the word:
The query only matches the following document:
Diacritic Sensitivity with Negated Term¶
The $diacriticSensitive option applies also to negated terms. A
negated term is a term that is prefixed by a minus sign -. If you
negate a term, the $text operator will exclude the documents that
contain those terms from the results.
The following query performs a diacritic sensitive text search for
document that contains the term leches but not the term cafés,
or more precisely the stemmed version of the words:
The query matches the following document:
Return the Text Search Score¶
The following query searches for the term cake and returns the
score assigned to each matching document:
The returned document includes an additional field score that
contains the document’s score associated with the text search.
[1]
See also
Sort by Text Search Score¶
To sort by the text score, include the same $meta
expression in both the projection document and the sort expression.
[1] The following query searches for the term coffee
and sorts the results by the descending score:
The query returns the matching documents sorted by descending score.
See also
Return Top 2 Matching Documents¶
Use the limit() method in conjunction with a
sort() to return the top n matching documents.
The following query searches for the term coffee and sorts the
results by the descending score, limiting the results to the top two
matching documents:
See also
Text Search with Additional Query and Sort Expressions¶
The following query searches for documents where the author equals
"xyz" and the indexed field subject contains the terms
coffee or bake. The operation also specifies a sort order of
ascending date, then descending text search score:
| [1] | (1, 2) The behavior and requirements of the $meta projection
operator differ from that of the $meta aggregation
operator. For details on the $meta aggregation operator,
see the $meta aggregation operator reference page. |