Native protocol column types

See Data Types for general reference.

팁

Numeric types encoding matches memory layout of little endian CPUs like AMD64 or ARM64, allowing very efficient encoding and decoding.

Type	Encoding
Integers (Int/UInt)	8, 16, 32, 64, 128 or 256 bits in little endian
Floats (Float32/Float64)	IEEE 754 binary representation
String	Array of strings as (len, value)
FixedString(N)	Array of N-byte sequences
IPv4	Alias of `UInt32`, represented as UInt32
IPv6	Alias of `FixedString(16)`, represented as binary
Tuple	Array of columns encoded continuously. Example: `Tuple(String, UInt8)` = two continuous columns
Map	`Map(K, V)` = three columns: `Offsets ColUInt64, Keys K, Values V`. Row count in Keys/Values = last Offsets value
Array	`Array(T)` = two columns: `Offsets ColUInt64, Data T`. Row count in Data = last Offsets value
Nullable	`Nullable(T)` = two columns: `Nulls ColUInt8, Values T` with same row count. Nulls is mask: 1=null, 0=value
UUID	Alias of `FixedString(16)`, represented as binary
Enum	Alias of `Int8` or `Int16`, each integer mapped to a String value
LowCardinality	`LowCardinality(T)` = two columns: `Index T, Keys K` where K is UInt8/16/32/64. Index contains unique values, Keys contains indexes into Index
Bool	Alias of `UInt8`: 0=false, 1=true

Example: Nullable encoding

To encode [null, "", "hello", null, "world"]:
  Values: ["", "", "hello", "", "world"] (len: 5)
  Nulls:  [ 1,  0,       0,  1,       0] (len: 5)

Example: LowCardinality encoding

To encode ["Eko", "Eko", "Amadela", "Amadela", "Amadela", "Amadela"]:
  Index: ["Eko", "Amadela"] (String)
  Keys:  [0, 0, 1, 1, 1, 1] (UInt8)