$bit

Definition

$bit

The $bit operator performs a bitwise update of a field. The operator supports bitwise and, bitwise or, and bitwise xor (i.e. exclusive or) operations. To specify a $bit operator expression, use the following prototype:

{ $bit: { <field>: { <and|or|xor>: <int> } } }

Only use this operator with integer fields (either 32-bit integer or 64-bit integer).

To specify a <field> in an embedded document or in an array, use dot notation.

Note

All numbers in mongosh are doubles, not integers. To to specify integers in mongosh, use the NumberInt() or the NumberLong() constructor. To learn more, see Int32 or Long.

To learn how your MongoDB driver handles numeric values, refer to your driver's documentation.

Behavior

Starting in MongoDB 5.0, mongod no longer raises an error when you use an update operator like $bit with an empty operand expression ( { } ). An empty update results in no changes and no oplog entry is created (meaning that the operation is a no-op).

Starting in MongoDB 5.0, update operators process document fields with string-based names in lexicographic order. Fields with numeric names are processed in numeric order. See Update Operators Behavior for details.

Examples

The following examples use the switches collection:

db.switches.insertMany( [
   { _id: 1, expdata: Int32(13) },
   { _id: 2, expdata: Int32(3) },
   { _id: 3, expdata: Int32(1) }
] )

db.switches.updateOne(
   { _id: 1 },
   { $bit: { expdata: { and: Int32( 10 ) } } }
)

1101   // expdata
1010   // Int32(10)
----
1000

{ "_id" : 1, "expdata" : 8 }

db.switches.updateOne(
   { _id: 2 },
   { $bit: { expdata: { or: Int32( 5 ) } } }
)

0111   // expdata
0101   // Int32(5)
----
0111

{ "_id" : 2, "expdata" : 7 }

db.switches.updateOne(
   { _id: 3 },
   { $bit: { expdata: { xor: Int32( 5 ) } } }
)

0001   // expdata
0101   // Int32(5)
----
0100

{ "_id" : 1, "expdata" : 4 }