Clickhouse
Tools to query and explore a ClickHouse database
1.0.1ClickHouse Toolkit
Arcade toolkit for connecting to and querying a ClickHouse database — enabling schema discovery, table exploration, and read-only SQL execution.
Capabilities
- Database & schema discovery: Enumerate all databases and retrieve schema information (returns a default schema name, since ClickHouse does not use PostgreSQL-style schemas).
- Table discovery: List all tables in the database; intended to be run before any query so exact table names are known.
- Schema inspection: Fetch the full structure of a specific table, including column names and types, before constructing queries.
- Read-only query execution: Run
SELECTstatements with full support for joins, filtering, ordering, pagination (LIMIT/OFFSET), and aggregation (HAVING); no write operations (INSERT,UPDATE,DELETE) are permitted.
Secrets
CLICKHOUSE_DATABASE_CONNECTION_STRING — A connection string that encodes all credentials and connection parameters needed to reach your ClickHouse instance. ClickHouse supports multiple connection string formats depending on the client driver; a typical format is clickhouse://[user]:[password]@[host]:[port]/[database] or the HTTP-equivalent http://[user]:[password]@[host]:[port]/[database]. Obtain the host, port, default database, and credentials from your ClickHouse deployment — for ClickHouse Cloud, find these on the Connect page of your service in the ClickHouse Cloud console; for self-hosted instances, consult your administrator or your server's config.xml / users.xml. Ensure the user has at minimum SELECT privileges on the target database and tables.
For configuring secrets in Arcade, see Tool Secrets. 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 |