Clickhouse
Tools to query and explore a ClickHouse database
1.0.2ClickHouse Toolkit
Arcade's ClickHouse toolkit connects agents to a ClickHouse database, enabling schema discovery and read-only SQL querying.
Capabilities
- Database & table discovery: List all databases, enumerate tables when names are unknown, and retrieve per-table schemas before constructing queries.
- Schema introspection: Returns a default schema name for ClickHouse (which lacks PostgreSQL-style schemas), keeping tool interfaces consistent across database toolkits.
- Read-only querying: Execute
SELECTstatements with structured clause inputs (select, from, join, where, having, order by, limit, offset); insert/update/delete operations are blocked. - Query safety guardrails: Enforces best practices at the tool level — no
SELECT *, mandatory ordering, case-insensitive string matching, trimming,LIKEover regex, and index-only joins.
Secrets
CLICKHOUSE_DATABASE_CONNECTION_STRING — The full connection string used to authenticate and connect to your ClickHouse instance. This typically takes the form of a DSN or URL that includes the protocol, username, password, host, port, and target database (e.g., clickhouse://user:password@host:8123/database). You obtain this by locating or creating a ClickHouse user with appropriate read permissions in your ClickHouse environment — either via ClickHouse Cloud or a self-hosted instance — then assembling the connection string from those credentials and your instance's host/port details. Ensure the user has at least SELECT privileges on the target database and tables.
For guidance on storing secrets in Arcade, see https://docs.arcade.dev/en/guides/create-tools/tool-basics/create-tool-secrets. You can manage your secrets 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 |