cursor.collation() (original) (raw)

cursor.collation(<collation document>)

Important

mongosh Method

This page documents a mongosh method. This is _not_the documentation for a language-specific driver, such as Node.js.

For MongoDB API drivers, refer to the language-specificMongoDB driver documentation.

Specifies the collation for the cursor returned by the db.collection.find(). To use, append to thedb.collection.find().

The cursor.collation() accepts the following collation document:


{

   locale: <string>,

   caseLevel: <boolean>,

   caseFirst: <string>,

   strength: <int>,

   numericOrdering: <boolean>,

   alternate: <string>,

   maxVariable: <string>,

   backwards: <boolean>

}

When specifying collation, the locale field is mandatory; all other collation fields are optional. For descriptions of the fields, see Collation Document.

Field Type Description
locale string The ICU locale. See Supported Languages and Locales for a list of supported locales.To specify simple binary comparison, specify locale value of"simple".
strength integer Optional. The level of comparison to perform. Corresponds to ICU Comparison Levels. Possible values are:ValueDescription1Primary level of comparison. Collation performs comparisons of the base characters only, ignoring other differences such as diacritics and case.2Secondary level of comparison. Collation performs comparisons up to secondary differences, such as diacritics. That is, collation performs comparisons of base characters (primary differences) and diacritics (secondary differences). Differences between base characters takes precedence over secondary differences.3Tertiary level of comparison. Collation performs comparisons up to tertiary differences, such as case and letter variants. That is, collation performs comparisons of base characters (primary differences), diacritics (secondary differences), and case and variants (tertiary differences). Differences between base characters takes precedence over secondary differences, which takes precedence over tertiary differences.This is the default level.4Quaternary Level. Limited for specific use case to consider punctuation when levels 1-3 ignore punctuation or for processing Japanese text.5Identical Level. Limited for specific use case of tie breaker.See ICU Collation: Comparison Levelsfor details.
caseLevel boolean Optional. Flag that determines whether to include case comparison atstrength level 1 or 2.If true, include case comparison; i.e.When used with strength:1, collation compares base characters and case.When used with strength:2, collation compares base characters, diacritics (and possible other secondary differences) and case.If false, do not include case comparison at level 1 or2. The default is false.For more information, see ICU Collation: Case Level.
caseFirst string Optional. A field that determines sort order of case differences during tertiary level comparisons.Possible values are:ValueDescription"upper"Uppercase sorts before lowercase."lower"Lowercase sorts before uppercase."off"Default value. Similar to "lower" with slight differences. Seehttps://unicode-org.github.io/icu/userguide/strings/properties.html#customizationfor details of differences.
numericOrdering boolean Optional. Flag that determines whether to compare numeric strings as numbers or as strings.If true, compare as numbers; i.e. "10" is greater than"2".If false, compare as strings; i.e. "10" is less than "2".Default is false.
alternate string Optional. Field that determines whether collation should consider whitespace and punctuation as base characters for purposes of comparison.Possible values are:ValueDescription"non-ignorable"Whitespace and punctuation are considered base characters."shifted"Whitespace and punctuation are not considered base characters and are only distinguished at strength levels greater than 3.See ICU Collation: Comparison Levelsfor more information.Default is "non-ignorable".
maxVariable string Optional. Field that determines up to which characters are considered ignorable when alternate: "shifted". Has no effect ifalternate: "non-ignorable"Possible values are:ValueDescription"punct"Both whitespaces and punctuation are "ignorable", i.e. not considered base characters."space"Whitespace are "ignorable", i.e. not considered base characters.
backwards boolean Optional. Flag that determines whether strings with diacritics sort from back of the string, such as with some French dictionary ordering.If true, compare from back to front.If false, compare from front to back.The default value is false.
normalization boolean Optional. Flag that determines whether to check if text require normalization and to perform normalization. Generally, majority of text does not require this normalization processing.If true, check if fully normalized and perform normalization to compare text.If false, does not check.The default value is false.Seehttps://unicode-org.github.io/icu/userguide/collation/concepts.html#normalization for details.

This method is available in deployments hosted in the following environments:

Note

This command is supported in all MongoDB Atlas clusters. For information on Atlas support for all commands, seeUnsupported Commands.

Consider a collection foo with the following documents:


{ "_id" : 1, "x" : "a" }

{ "_id" : 2, "x" : "A" }

{ "_id" : 3, "x" : "á" }

The following operation specifies a query filter of x: "a". The operation also includes a collation option with locale: "en_US"(US English locale) and strength: 1 (compare base characters only; i.e. ignore case and diacritics):


db.foo.find( { x: "a" } ).collation( { locale: "en_US", strength: 1 } )

The operation returns the following documents:


{ "_id" : 1, "x" : "a" }

{ "_id" : 2, "x" : "A" }

{ "_id" : 3, "x" : "á" }

If you do not specify the collation, i.e. db.collection.find( { x: "a" } ), the query would only match the following document:


db.foo.find( { x: "a" } )

You can chain other cursor methods, such as cursor.sort()and cursor.count(), to cursor.collation():


db.collection.find({...}).collation({...}).sort({...});

db.collection.find({...}).collation({...}).count();

Note

You cannot specify multiple collations for an operation. For example, you cannot specify different collations per field, or if performing a find with a sort, you cannot use one collation for the find and another for the sort.