Docs Menu
Docs Home
/
MongoDB Manual
/ / / /

$bitsAllClear

On this page

  • Behavior
  • Examples
$bitsAllClear

$bitsAllClear matches documents where all of the bit positions given by the query are clear (i.e. 0) in field.

{ <field>: { $bitsAllClear: <numeric bitmask> } }
{ <field>: { $bitsAllClear: < BinData bitmask> } }
{ <field>: { $bitsAllClear: [ <position1>, <position2>, ... ] } }

The field value must be either numeric or a BinData instance. Otherwise, $bitsAllClear will not match the current document.

Numeric Bitmask
You can provide a numeric bitmask to be matched against the operand field. The bitmask must be a non-negative 64-bit signed integer. Otherwise, $bitsAllClear returns an error.
BinData Bitmask
You can also use an arbitrarily large BinData instance as a bitmask.
Position List
If querying a list of bit positions, each <position> must be a non-negative integer. Bit positions start at 0 from the least significant bit. For example, the decimal number 254 would have the following bit positions:
Bit Value
1
1
1
1
1
1
1
0
Position
7
6
5
4
3
2
1
0

The endianness of your system depends on the architecture of your machine. Numbers in BSON data are always stored as little-endian, if your system is big-endian this means that numeric data is converted between big and little endian.

In the context of the bit-test match expression operators:

BinData values act as bitmasks and are interpreted as though they are arbitrary-length unsigned little-endian numbers. The lowest-addressable byte is always interpreted as the least significant byte. Similarly, the highest-addressable byte in the BinData is always interpreted as the most significant byte.

Queries cannot use indexes for the $bitsAllClear portion of a query, although the other portions of a query can use indexes, if applicable.

$bitsAllClear will not match numerical values that cannot be represented as a signed 64-bit integer. This can be the case if a value is either too large or too small to fit in a signed 64-bit integer, or if it has a fractional component.

Numbers are sign extended. For example, $bitsAllClear considers bit position 200 to be set for the negative number -5, but bit position 200 to be clear for the positive number +5.

In contrast, BinData instances are zero-extended. For example, given the following document:

db.collection.insertOne({ x: BinData(0, "ww=="), binaryValueofA: "11000011" })

$bitsAllClear will consider all bits outside of x to be clear.

The following examples will use a collection with the following documents:

db.collection.insertMany([
{ _id: 1, a: 54, binaryValueofA: "00110110" },
{ _id: 2, a: 20, binaryValueofA: "00010100" },
{ _id: 3, a: 20.0, binaryValueofA: "00010100" },
{ _id: 4, a: BinData(0, "Zg=="), binaryValueofA: "01100110" }
])

The following query uses the $bitsAllClear operator to test whether field a has bits clear at position 1 and position 5, where the least significant bit is position 0.

db.collection.find( { a: { $bitsAllClear: [ 1, 5 ] } } )

The query matches the following documents:

{ "_id" : 2, "a" : 20, "binaryValueofA" : "00010100" }
{ "_id" : 3, "a" : 20, "binaryValueofA" : "00010100" }

The following query uses the $bitsAllClear operator to test whether field a has bits clear at positions 0, 1, and 5 (the binary representation of the bitmask 35 is 00100011).

db.collection.find( { a: { $bitsAllClear: 35 } } )

The query matches the following documents:

{ "_id" : 2, "a" : 20, "binaryValueofA" : "00010100" }
{ "_id" : 3, "a" : 20, "binaryValueofA" : "00010100" }

The following query uses the $bitsAllClear operator:

db.collection.find( { a: { $bitsAllClear: BinData(0, "IA==") } } )

The query:

  • Specifies 0 as the first value for BinData, which indicates IA== should be interpreted as binary. The base-64 value IA== in binary is 00100000, which has 1 in position 5.

  • Uses $bitsAllClear to return documents where the a field has a clear bit 0 in position 5 of the binary value.

The query returns the following documents:

{ "_id" : 2, "a" : 20, "binaryValueofA" : "00010100" }
{ "_id" : 3, "a" : 20, "binaryValueofA" : "00010100" }
← Bitwise Query Operators

On this page