$size

• $size
• The $size operator matches any array with the number ofelements specified by the argument. For example:

db.collection.find( { field: { $size: 2 } } );

returns all documents in collection where field is an arraywith 2 elements. For instance, the above expression willreturn { field: [ red, green ] } and { field: [ apple,lime ] } but not { field: fruit } or { field: [orange, lemon, grapefruit ] }. To match fields with only oneelement within an array use $size with a value of 1, asfollows:

db.collection.find( { field: { $size: 1 } } );

$size does not accept ranges of values. To selectdocuments based on fields with different numbers of elements,create a counter field that you increment when you add elements toa field.

Queries cannot use indexes for the $size portion of aquery, although the other portions of a query can use indexes ifapplicable.

Additional Examples

For additional examples in querying arrays, see:

• Query an Array
• Query an Array of Embedded Documents

For additional examples in querying, see:

• Query Documents

See also

db.collection.find()