Manipulating SAMPLE BY expression

The following operations are available:

MODIFY {#modify}

ALTER TABLE [db].name [ON CLUSTER cluster] MODIFY SAMPLE BY new_expression

The command changes the sampling key of the table to new_expression (an expression or a tuple of expressions). The primary key must contain the new sample key.

REMOVE {#remove}

ALTER TABLE [db].name [ON CLUSTER cluster] REMOVE SAMPLE BY

The command removes the sampling key of the table.

The commands MODIFY and REMOVE are lightweight in the sense that they only change metadata or remove files.

:::note
It only works for tables in the MergeTree family (including replicated tables). :::