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toc_priority | toc_title |
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41 | SAMPLE BY |
Manipulating Sampling-Key Expressions
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 command is lightweight in a sense that it only changes metadata. The primary key must contain the new sample key.
!!! note "Note"
It only works for tables in the MergeTree
family (including
replicated tables).