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- MongoDB\Collection::distinct()
MongoDB\Collection::distinct()
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Definition
-
MongoDB\Collection::distinct
Finds the distinct values for a specified field across the collection.
This method has the following parameters:
Parameter Type Description $fieldName
string The field for which to return distinct values. $filter
array|object Optional. The filter criteria that specifies the documents from which to retrieve the distinct values. $options
array Optional. An array specifying the desired options. The
$options
parameter supports the following options:Option Type Description collation
array|object Optional. Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks. When specifying collation, the
locale
field is mandatory; all other collation fields are optional. For descriptions of the fields, see Collation Document.If the collation is unspecified but the collection has a default collation, the operation uses the collation specified for the collection. If no collation is specified for the collection or for the operation, MongoDB uses the simple binary comparison used in prior versions for string comparisons.
comment
mixed Optional. Enables users to specify an arbitrary comment to help trace the operation through the database profiler, currentOp output, and logs.
This is not supported for server versions prior to 4.4 and will result in an exception at execution time if used.
New in version 1.13.
maxTimeMS
integer Optional. The cumulative time limit in milliseconds for processing operations on the cursor. MongoDB aborts the operation at the earliest following interrupt point. readConcern
MongoDB\Driver\ReadConcern Optional. Read concern to use for the operation. Defaults to the collection’s read concern.
It is not possible to specify a read concern for individual operations as part of a transaction. Instead, set the
readConcern
option when starting the transaction with startTransaction.readPreference
MongoDB\Driver\ReadPreference Optional. Read preference to use for the operation. Defaults to the collection’s read preference. session
MongoDB\Driver\Session Optional. Client session to associate with the operation.
New in version 1.3.
typeMap
array Optional. The type map to apply to cursors, which determines how BSON documents are converted to PHP values. Defaults to the collection’s type map.
New in version 1.5.
Return Values
An array of the distinct values.
Errors/Exceptions
MongoDB\Exception\UnexpectedValueException
if the command
response from the server was malformed.
MongoDB\Exception\UnsupportedException
if options are used and
not supported by the selected server (e.g. collation
, readConcern
,
writeConcern
).
MongoDB\Exception\InvalidArgumentException
for errors related to
the parsing of parameters or options.
MongoDB\Driver\Exception\RuntimeException for other errors at the driver level (e.g. connection errors).
Behavior
When evaluating query criteria, MongoDB compares types and values according to its own comparison rules for BSON types, which differs from PHP’s comparison and type juggling rules. When matching a special BSON type the query criteria should use the respective BSON class in the driver (e.g. use MongoDB\BSON\ObjectId to match an ObjectId).
Examples
Return Distinct Values for a Field
The following example identifies the distinct values for the borough
field
in the restaurants
collection in the test
database.
The output would then resemble:
Return Distinct Values Using a Filter
The following example identifies the distinct values for the cuisine
field
in the restaurants
collection in the test
database for documents where
the borough
is Queens
:
The output would then resemble:
See Also
- distinct command reference in the MongoDB manual