← Databases

ClickHouse

The driver talks to ClickHouse's HTTP interface and reads results in the Arrow stream format. It is part of the app; nothing is downloaded. It browses, queries and designs tables, but does not edit rows in the grid.

Connect

Use the HTTP port, not the native one (9000). The user is default when empty; the password is sent in the X-ClickHouse-Key header. The Database field runs USE <database> after connecting.

TLS is chosen by the mode, since HTTP cannot negotiate it: disable and prefer (the default) connect in plain HTTP; require and the verify modes use HTTPS. With HTTPS the default port is 8443 when the URL gives none; if you fill in the form, type the port yourself. require does not check the certificate, verify-ca checks the chain, verify-full also the host name; sslrootcert names your CA's file, otherwise the system's trusted certificates are used.

A connection is one HTTP session: SET, USE and temporary tables last between statements.

Privileges

Browsing reads system.databases, system.tables, system.columns and system.data_skipping_indices; the login sees what ClickHouse lets it see there. The tabs read:

• Parameters: system.settings and system.server_settings.
• Dashboard: system.metrics, system.events, system.parts (database sizes) and system.replicas; what the login cannot read shows "—".
• Users and roles: system.users, system.roles, system.grants and system.role_grants. Users defined in the server's configuration files are listed too; the server refuses to change them.

What works

• Queries, results, the navigator, autocompletion, object DDL, metadata search, and the table designer (including the engine clause and skipping indices).
• Explain shows the plan of EXPLAIN indexes = 1; there is no Explain analyze.
• Cancel stops the statement on the server with KILL QUERY.
• Parameters, Dashboard and Users and roles tabs. No sessions, locks, statements or tables and indexes tabs.
• Exports, and imports into ClickHouse as INSERT statements.

What does not

• No data editing in the grid: it says "ClickHouse tables are not edited in place". Saving would check each change's row count inside a transaction, and ClickHouse has neither transactions nor row counts for updates. Change rows with SQL.
• No transactions: the manual-commit toolbar is hidden; every statement takes effect alone.
• No foreign keys or unique constraints (the primary key only orders the data).

Agents

A read-only agent, and a read-only connection, send every statement except SET with readonly = 1, so the server refuses writes and the table functions that reach other servers or its files (url, s3, remote, file and the like). An agent's statement is also checked against a list of table functions that read local data only. See Agents and the CLI. Terminal mode is not available: clickhouse-client uses the native port.

Known limits

• Plain HTTP unless the mode is require or stronger: the default prefer does not encrypt.
• Only the HTTP interface is used; a server that exposes just the native port cannot be reached.

Tested on

The conformance suite runs on ClickHouse 26.3. Older ClickHouse versions are not tested, and the app has no minimum version for it.

See also: Connecting, Troubleshooting.