mutations_* session settings - ClickHouse Documentation

These settings are available in system.settings and are autogenerated from source.

mutations_max_literal_size_to_replace

The maximum size of serialized literal in bytes to replace in UPDATE and DELETE queries. Takes effect only if at least one the two settings above is enabled. Default value: 16384 (16 KiB).

mutations_sync

Controls how the client waits for mutations created by ALTER TABLE operations such as UPDATE, DELETE, MATERIALIZE INDEX, MATERIALIZE PROJECTION, MATERIALIZE COLUMN, and MATERIALIZE STATISTICS. Possible values:

Value	Description
`0`	Mutations execute asynchronously.
`1`	The query waits for all mutations to complete on the current server.
`2`	The query waits for all mutations to complete on all replicas (if they exist).
`3`	The query waits only for the active replicas. Inactive replicas apply the mutations when they become active.

Last modified on September 25, 2026