Clickhouse
Tools to query and explore a ClickHouse database
1.0.2ClickHouse Toolkit
Arcade's ClickHouse toolkit provides tools to connect to and explore a ClickHouse database, enabling schema discovery and read-only SQL query execution.
Capabilities
- Database & schema discovery: List all databases and retrieve default schema information (ClickHouse does not use schemas like PostgreSQL).
- Table discovery & schema inspection: Enumerate tables when they are unknown, and fetch the full structure of a specific table before querying.
- Read-only query execution: Run
SELECTqueries with structured clause composition (joins, filters, ordering, pagination); no write operations are permitted.
Secrets
CLICKHOUSE_DATABASE_CONNECTION_STRING — A connection string (DSN) used to authenticate and connect to the ClickHouse instance. It typically follows the format clickhouse://[user]:[password]@[host]:[port]/[database] and encodes the host, port, database name, username, and password in a single string. Obtain or construct this value from your ClickHouse deployment's connection details — for cloud-hosted instances (e.g., ClickHouse Cloud), find the host and credentials in the ClickHouse Cloud console under your service's Connection details section. For self-hosted instances, use the host/port you configured during setup along with the user credentials defined in your ClickHouse users.xml or via SQL user management.
Store this secret in Arcade as described in the Arcade secrets guide. You can also manage secrets directly at https://api.arcade.dev/dashboard/auth/secrets.
Available tools(5)
| Tool name | Description | Secrets | |
|---|---|---|---|
Discover all the databases in the ClickHouse database. | 1 | ||
Discover all the schemas in the ClickHouse database.
Note: ClickHouse doesn't have schemas like PostgreSQL, so this returns a default schema name. | 1 | ||
Discover all the tables in the ClickHouse database when the list of tables is not known.
ALWAYS use this tool before any other tool that requires a table name. | 1 | ||
You have a connection to a ClickHouse database.
Execute a SELECT query and return the results against the ClickHouse database.
No other queries (INSERT, UPDATE, DELETE, etc.) are allowed.
ONLY use this tool if you have already loaded the schema of the tables you need to query.
The final query will be constructed as follows:
SELECT {select_query_part} FROM {from_clause} JOIN {join_clause}
WHERE {where_clause} HAVING {having_clause}
ORDER BY {order_by_clause} LIMIT {limit} OFFSET {offset}
When running queries, follow these rules which will help avoid errors:
* Never "select *" from a table. Always select the columns you need.
* Always order your results. Use the most important columns or the primary key if you're unsure.
* Always use case-insensitive queries to match strings in the query.
* Always trim strings in the query.
* Prefer LIKE queries over direct string matches or regex queries.
* Only join on columns that are indexed or the primary key. Do not join on arbitrary columns.
* ClickHouse is case-sensitive, so be careful with table and column names. | 1 | ||
Get the schema/structure of a ClickHouse table in the ClickHouse database
when the schema is not known, and the name of the table is provided.
This tool should ALWAYS be used before executing any query.
All tables in the query must be discovered first,
so that their exact names are known. | 1 |