Common ClickHouse Errors and Exceptions

General Errors

`DB::Exception: Not enough space` – Insufficient disk space.
DB::Exception: Memory limit exceeded – Query exceeds memory limits.
DB::Exception: Too many parts – Too many active data parts in a table, causing performance issues.
DB::Exception: Table is in readonly mode – The table is in read-only mode due to metadata issues or storage settings.
DB::Exception: Cannot load table – Table metadata is corrupted or missing.
DB::Exception: Table structure does not match – Schema mismatch when attaching a table.
`DB::Exception: Not found column` – Query references a non-existent column.
DB::Exception: Directory already exists – Issue when creating or renaming tables with existing directories.

`Syntax error: failed at position X` – Incorrect SQL syntax.
`DB::Exception: Aggregate function requires parameters` – Missing or incorrect arguments for an aggregate function.
DB::Exception: Unknown function – Using an undefined function.
`DB::Exception: Invalid number of arguments` – Function called with an incorrect number of arguments.
`DB::Exception: Division by zero` – Attempting to divide by zero.
`DB::Exception: Nested type mismatch` – Type mismatch in nested structures like Array(Tuple(...)).

`DB::Exception: Too many parts (merge is lagging)` – Table has too many small parts, causing merge issues.
`DB::Exception: Replica is lost` – Replicated table lost its metadata or connection to the cluster.
DB::Exception: ZooKeeper node exists – Replication conflict with existing metadata.
DB::Exception: Cannot create a new ZooKeeper session – ClickHouse cannot connect to ZooKeeper.
DB::Exception: No active replicas – All replicas of a table are down or lagging.
`DB::Exception: Unknown status of replica` – ClickHouse cannot determine the replica's state.

`DB::Exception: Access denied` – User lacks the necessary privileges.
`DB::Exception: User does not exist` – Attempting to authenticate with a non-existent user.
DB::Exception: Wrong password – Incorrect password provided for authentication.
DB::Exception: Cannot write to table – Write operation denied due to permission restrictions.

`DB::Exception: Connection refused` – ClickHouse server is unreachable.
`DB::Exception: Read timeout` – Query exceeded network timeout.
DB::Exception: Cannot read from socket – Network failure while fetching data.
DB::Exception: Too many simultaneous connections – Exceeded the maximum allowed client connections.

`DB::Exception: Cannot merge parts` – Merge operation failure due to disk issues or corrupted data.
`DB::Exception: Merge is manually disabled` – Merge operations disabled for the table.
`DB::Exception: Part is already merged into another part` – Data inconsistency in a ReplicatedMergeTree table.
`DB::Exception: Part is not in expected state` – MergeTree part is in an unexpected state.

`DB::Exception: Cannot parse JSON` – JSON data format is invalid.
`DB::Exception: Cannot parse DateTime` – Incorrect date/time format in an insert or query.
`DB::Exception: Type mismatch` – Provided data type does not match the column type.
`DB::Exception: Cannot convert` – Conversion between incompatible types.
`DB::Exception: Data too large for column` – Inserted data exceeds the column’s defined size.

DB::Exception: There is no query for id – The distributed query ID is not found.
`DB::Exception: Shard is unavailable` – One or more shards in a distributed table are down.
DB::Exception: Distributed query execution failed – General failure in a distributed query.