Data types on disk and in RAM

DataTypeRAM size (=byteSize)Disk Size
String

string byte length + 9

string length: 64 bit integer

zero-byte terminator: 1 byte.

string length prefix (varint) + string itself:


string shorter than 128 - string byte length + 1
string shorter than 16384 - string byte length + 2
string shorter than 2097152 - string byte length + 2
string shorter than 268435456 - string byte length + 4

AggregateFunction(count, ...)varint

See also the presentation Data processing into ClickHouse®, especially slides 17-22.

Last modified 2024.07.29: Site cleanup, mostly minor changes (3e41a19)