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$size
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$size
The
$size
operator matches any array with the number of elements specified by the argument. For example:db.collection.find( { field: { $size: 2 } } ); returns all documents in
collection
wherefield
is an array with 2 elements. For instance, the above expression will return{ field: [ red, green ] }
and{ field: [ apple, lime ] }
but not{ field: fruit }
or{ field: [ orange, lemon, grapefruit ] }
. To match fields with only one element within an array use$size
with a value of 1, as follows:db.collection.find( { field: { $size: 1 } } ); $size
does not accept ranges of values. To select documents based on fields with different numbers of elements, create a counter field that you increment when you add elements to a field.Queries cannot use indexes for the
$size
portion of a query, although the other portions of a query can use indexes if applicable.
Additional Examples
For additional examples in querying arrays, see:
For additional examples in querying, see: