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Propagate Query and Session Settings for Distributed DDL Queries in ClickHouse

Official CH changelog text
Propagate query and session settings for distributed DDL queries. Set distributed_ddl_entry_format_version to 2 to enable this. Added distributed_ddl_output_mode setting. Supported modes: none, throw (default), null_status_on_timeout and never_throw. Miscellaneous fixes and improvements for Replicated database engine. #21535 (tavplubix).
Introduces propagation of query and session settings for distributed DDL queries in ClickHouse, controlled by the distributed_ddl_entry_format_version setting. Adds a new distributed_ddl_output_mode setting with multiple modes to control output behavior for distributed DDL operations. Includes various fixes and improvements for the Replicated database engine.

Why it matters

This feature enables better control and consistency when executing distributed Data Definition Language (DDL) queries across a cluster by propagating query and session settings. It addresses issues with handling distributed DDL outputs and error reporting through configurable modes, improving the reliability and usability of distributed schema changes. The improvements to the Replicated engine enhance stability and robustness for replicated database clusters.

How to use it

To enable query and session settings propagation for distributed DDL queries, set the configuration parameter distributed_ddl_entry_format_version to 2. Adjust the behavior of distributed DDL output handling by configuring distributed_ddl_output_mode with one of the supported modes: none, throw (default), null_status_on_timeout, or never_throw. These settings can be applied in the server configuration or via session settings.

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