Set up docs MCPThese settings are available in system.settings and are autogenerated from the ClickHouse snapshot.
lightweight_delete_mode
A mode of internal update query that is executed as a part of lightweight delete.
Possible values:
alter_update- runALTER UPDATEquery that creates a heavyweight mutation.lightweight_update- run lightweight update if possible, runALTER UPDATEotherwise.lightweight_update_force- run lightweight update if possible, throw otherwise.
For DELETE FROM ... ON CLUSTER, each executing host derives the mode from its own settings, so
hosts whose profiles set different defaults can run the delete in different modes. A replicated
shard executes on one replica, so there it is that replica’s settings that decide. Setting it in
the session of the initiating query overrides this, because the distributed DDL entry carries
session changes at distributed_ddl_entry_format_version 2 and above, which the default satisfies.
A host that constrains the setting clamps the value back.
lightweight_deletes_sync
The same as mutations_sync, but controls only execution of lightweight deletes.
Possible values:
| Value | Description |
|---|---|
0 |
Mutations execute asynchronously. |
1 |
The query waits for the lightweight deletes to complete on the current server. |
2 |
The query waits for the lightweight deletes to complete on all replicas (if they exist). |
3 |
The query waits only for the active replicas. Inactive replicas apply the lightweight deletes when they become active. |
See Also
Cloud default value: 1.