Skip using 'ON CLUSTER' in case of DB Engine is 'Replicated'#119
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911limbo wants to merge 1 commit intoflyway:mainfrom
Open
Skip using 'ON CLUSTER' in case of DB Engine is 'Replicated'#119911limbo wants to merge 1 commit intoflyway:mainfrom
911limbo wants to merge 1 commit intoflyway:mainfrom
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Summary
ClickHouse throws the following error when executing DDL with
ON CLUSTERinside a database created withENGINE = Replicated(...):Code: 48. DB::Exception: ON CLUSTER is not allowed for Replicated databaseReplicated databases already propagate DDL statements automatically via the database engine, therefore adding
ON CLUSTERis invalid.What this PR does
This change detects whether the target database uses the
Replicatedengine (via system.databases) and skips addingON CLUSTERin that case.The check is executed using the dedicated system connection to avoid issues when the target database does not yet exist.
Why this is needed
Flyway adds
ON CLUSTERto DDL statements when a cluster is configured.However, if the target database is created with
ENGINE = Replicated(...),ClickHouse does not allow using
ON CLUSTER, because DDL replicationis already handled by the database engine itself.
As a result, migrations fail with:
Code: 48. DB::Exception: ON CLUSTER is not allowed for Replicated databaseCompatibility
No behavior change for non-Replicated databases
No change for users who do not configure a cluster
Safe for databases that are not yet created