Clickhouse
Tools to query and explore a ClickHouse database
1.0.1ClickHouse Toolkit
Arcade toolkit that connects to a ClickHouse database to enable discovery and read-only querying of its structure and data.
Capabilities
- Database & table discovery: List all databases, retrieve available tables when table names are unknown, and inspect table schemas before constructing queries.
- Schema introspection: Retrieve column-level structure for any named table; ClickHouse lacks PostgreSQL-style schemas, so schema discovery returns a default schema name.
- Read-only query execution: Run parameterized
SELECTstatements with full support forJOIN,WHERE,HAVING,ORDER BY,LIMIT, andOFFSETclauses; no write operations (INSERT, UPDATE, DELETE) are permitted. - Query safety guardrails: Built-in conventions enforce column-specific selection (no
SELECT *), case-insensitive and trimmed string matching,LIKE-preferred filtering, and index/primary-key-only joins to minimize errors against ClickHouse's case-sensitive engine.
Secrets
CLICKHOUSE_DATABASE_CONNECTION_STRING — The full connection string used to authenticate and connect to your ClickHouse instance. For ClickHouse Cloud or self-hosted deployments this typically takes the form of a DSN or URL that encodes the host, port, username, password, and target database (e.g., clickhouse://user:password@host:port/database). Obtain this from your ClickHouse Cloud console under Settings → Connection String, or construct it manually from your self-hosted cluster credentials. Refer to the ClickHouse connection string documentation for format details.
Store secrets in Arcade at https://docs.arcade.dev/en/guides/create-tools/tool-basics/create-tool-secrets or via the dashboard 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 |