ClickHouse/docs/en/sql-reference/functions/bit-functions.md

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48	Bit

Bit Functions

Bit functions work for any pair of types from UInt8, UInt16, UInt32, UInt64, Int8, Int16, Int32, Int64, Float32, or Float64. Some functions support String and FixedString types.

The result type is an integer with bits equal to the maximum bits of its arguments. If at least one of the arguments is signed, the result is a signed number. If an argument is a floating-point number, it is cast to Int64.

bitAnd(a, b)

bitOr(a, b)

bitXor(a, b)

bitNot(a)

bitShiftLeft(a, b)

Shifts the binary representation of a value to the left by a specified number of bit positions.

A FixedString or a String is treated as a single multibyte value.

Bits of a FixedString value are lost as they are shifted out. On the contrary, a String value is extended with additional bytes, so no bits are lost.

Syntax

bitShiftLeft(a, b)

Arguments

• a — A value to shift. Integer types, String or FixedString.
• b — The number of shift positions. Unsigned integer types, 64 bit types or less are allowed.

Returned value

• Shifted value.

The type of the returned value is the same as the type of the input value.

Example

In the following queries bin and hex functions are used to show bits of shifted values.

SELECT 99 AS a, bin(a), bitShiftLeft(a, 2) AS a_shifted, bin(a_shifted);
SELECT 'abc' AS a, hex(a), bitShiftLeft(a, 4) AS a_shifted, hex(a_shifted);
SELECT toFixedString('abc', 3) AS a, hex(a), bitShiftLeft(a, 4) AS a_shifted, hex(a_shifted);

Result:

┌──a─┬─bin(99)──┬─a_shifted─┬─bin(bitShiftLeft(99, 2))─┐
│ 99 │ 01100011 │       140 │ 10001100                 │
└────┴──────────┴───────────┴──────────────────────────┘
┌─a───┬─hex('abc')─┬─a_shifted─┬─hex(bitShiftLeft('abc', 4))─┐
│ abc │ 616263     │ &0        │ 06162630                    │
└─────┴────────────┴───────────┴─────────────────────────────┘
┌─a───┬─hex(toFixedString('abc', 3))─┬─a_shifted─┬─hex(bitShiftLeft(toFixedString('abc', 3), 4))─┐
│ abc │ 616263                       │ &0        │ 162630                                        │
└─────┴──────────────────────────────┴───────────┴───────────────────────────────────────────────┘

bitShiftRight(a, b)

Shifts the binary representation of a value to the right by a specified number of bit positions.

A FixedString or a String is treated as a single multibyte value. Note that the length of a String value is reduced as bits are shifted out.

Syntax

bitShiftRight(a, b)

Arguments

• a — A value to shift. Integer types, String or FixedString.
• b — The number of shift positions. Unsigned integer types, 64 bit types or less are allowed.

Returned value

• Shifted value.

The type of the returned value is the same as the type of the input value.

Example

Query:

SELECT 101 AS a, bin(a), bitShiftRight(a, 2) AS a_shifted, bin(a_shifted);
SELECT 'abc' AS a, hex(a), bitShiftRight(a, 12) AS a_shifted, hex(a_shifted);
SELECT toFixedString('abc', 3) AS a, hex(a), bitShiftRight(a, 12) AS a_shifted, hex(a_shifted);

Result:

┌───a─┬─bin(101)─┬─a_shifted─┬─bin(bitShiftRight(101, 2))─┐
│ 101 │ 01100101 │        25 │ 00011001                   │
└─────┴──────────┴───────────┴────────────────────────────┘
┌─a───┬─hex('abc')─┬─a_shifted─┬─hex(bitShiftRight('abc', 12))─┐
│ abc │ 616263     │           │ 0616                          │
└─────┴────────────┴───────────┴───────────────────────────────┘
┌─a───┬─hex(toFixedString('abc', 3))─┬─a_shifted─┬─hex(bitShiftRight(toFixedString('abc', 3), 12))─┐
│ abc │ 616263                       │           │ 000616                                          │
└─────┴──────────────────────────────┴───────────┴─────────────────────────────────────────────────┘

bitRotateLeft(a, b)

bitRotateRight(a, b)

bitSlice(s, offset, length)

Returns a substring starting with the bit from the ‘offset’ index that is ‘length’ bits long. bits indexing starts from 1

Syntax

bitSlice(s, offset[, length])

Arguments

• s — s is String or FixedString.
• offset — The start index with bit, A positive value indicates an offset on the left, and a negative value is an indent on the right. Numbering of the bits begins with 1.
• length — The length of substring with bit. If you specify a negative value, the function returns an open substring [ offset, array_length - length). If you omit the value, the function returns the substring [offset, the_end_string]. If length exceeds s, it will be truncate.If length isn't multiple of 8, will fill 0 on the right.

Returned value

• The substring. String

Example

Query:

select bin('Hello'), bin(bitSlice('Hello', 1, 8))
select bin('Hello'), bin(bitSlice('Hello', 1, 2))
select bin('Hello'), bin(bitSlice('Hello', 1, 9))
select bin('Hello'), bin(bitSlice('Hello', -4, 8))

Result:

┌─bin('Hello')─────────────────────────────┬─bin(bitSlice('Hello', 1, 8))─┐
│ 0100100001100101011011000110110001101111 │ 01001000                     │
└──────────────────────────────────────────┴──────────────────────────────┘
┌─bin('Hello')─────────────────────────────┬─bin(bitSlice('Hello', 1, 2))─┐
│ 0100100001100101011011000110110001101111 │ 01000000                     │
└──────────────────────────────────────────┴──────────────────────────────┘
┌─bin('Hello')─────────────────────────────┬─bin(bitSlice('Hello', 1, 9))─┐
│ 0100100001100101011011000110110001101111 │ 0100100000000000             │
└──────────────────────────────────────────┴──────────────────────────────┘
┌─bin('Hello')─────────────────────────────┬─bin(bitSlice('Hello', -4, 8))─┐
│ 0100100001100101011011000110110001101111 │ 11110000                      │
└──────────────────────────────────────────┴───────────────────────────────┘

bitTest

Takes any integer and converts it into binary form, returns the value of a bit at specified position. The countdown starts from 0 from the right to the left.

Syntax

SELECT bitTest(number, index)

Arguments

• number – Integer number.
• index – Position of bit.

Returned values

Returns a value of bit at specified position.

Type: UInt8.

Example

For example, the number 43 in base-2 (binary) numeral system is 101011.

Query:

SELECT bitTest(43, 1);

Result:

┌─bitTest(43, 1)─┐
│              1 │
└────────────────┘

Another example:

Query:

SELECT bitTest(43, 2);

Result:

┌─bitTest(43, 2)─┐
│              0 │
└────────────────┘

bitTestAll

Returns result of logical conjuction (AND operator) of all bits at given positions. The countdown starts from 0 from the right to the left.

The conjuction for bitwise operations:

0 AND 0 = 0

0 AND 1 = 0

1 AND 0 = 0

1 AND 1 = 1

Syntax

SELECT bitTestAll(number, index1, index2, index3, index4, ...)

Arguments

• number – Integer number.
• index1, index2, index3, index4 – Positions of bit. For example, for set of positions (index1, index2, index3, index4) is true if and only if all of its positions are true (index1 ⋀ index2, ⋀ index3 ⋀ index4).

Returned values

Returns result of logical conjuction.

Type: UInt8.

Example

For example, the number 43 in base-2 (binary) numeral system is 101011.

Query:

SELECT bitTestAll(43, 0, 1, 3, 5);

Result:

┌─bitTestAll(43, 0, 1, 3, 5)─┐
│                          1 │
└────────────────────────────┘

Another example:

Query:

SELECT bitTestAll(43, 0, 1, 3, 5, 2);

Result:

┌─bitTestAll(43, 0, 1, 3, 5, 2)─┐
│                             0 │
└───────────────────────────────┘

bitTestAny

Returns result of logical disjunction (OR operator) of all bits at given positions. The countdown starts from 0 from the right to the left.

The disjunction for bitwise operations:

0 OR 0 = 0

0 OR 1 = 1

1 OR 0 = 1

1 OR 1 = 1

Syntax

SELECT bitTestAny(number, index1, index2, index3, index4, ...)

Arguments

• number – Integer number.
• index1, index2, index3, index4 – Positions of bit.

Returned values

Returns result of logical disjuction.

Type: UInt8.

Example

For example, the number 43 in base-2 (binary) numeral system is 101011.

Query:

SELECT bitTestAny(43, 0, 2);

Result:

┌─bitTestAny(43, 0, 2)─┐
│                    1 │
└──────────────────────┘

Another example:

Query:

SELECT bitTestAny(43, 4, 2);

Result:

┌─bitTestAny(43, 4, 2)─┐
│                    0 │
└──────────────────────┘

bitCount

Calculates the number of bits set to one in the binary representation of a number.

Syntax

bitCount(x)

Arguments

• x — Integer or floating-point number. The function uses the value representation in memory. It allows supporting floating-point numbers.

Returned value

• Number of bits set to one in the input number.

The function does not convert input value to a larger type (sign extension). So, for example, bitCount(toUInt8(-1)) = 8.

Type: UInt8.

Example

Take for example the number 333. Its binary representation: 0000000101001101.

Query:

SELECT bitCount(333);

Result:

┌─bitCount(333)─┐
│             5 │
└───────────────┘

bitHammingDistance

Returns the Hamming Distance between the bit representations of two integer values. Can be used with SimHash functions for detection of semi-duplicate strings. The smaller is the distance, the more likely those strings are the same.

Syntax

bitHammingDistance(int1, int2)

Arguments

• int1 — First integer value. Int64.
• int2 — Second integer value. Int64.

Returned value

• The Hamming distance.

Type: UInt8.

Examples

Query:

SELECT bitHammingDistance(111, 121);

Result:

┌─bitHammingDistance(111, 121)─┐
│                            3 │
└──────────────────────────────┘

With SimHash:

SELECT bitHammingDistance(ngramSimHash('cat ate rat'), ngramSimHash('rat ate cat'));

Result:

┌─bitHammingDistance(ngramSimHash('cat ate rat'), ngramSimHash('rat ate cat'))─┐
│                                                                            5 │
└──────────────────────────────────────────────────────────────────────────────┘