Connect ClickHouse

The Clickhouse source reads tables from a ClickHouse server into the Lake. It connects over the server's HTTP interface, or HTTPS with SSL/TLS on. Use this page to fill in each field of the Clickhouse form. The steps shared by every SQL engine are on Connect a SQL database.

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Prerequisites

• A ClickHouse user with read access to the databases and tables you want to load.
• The server's HTTP interface accepts connections from DataMind, usually on port 8123, or 8443 for HTTPS.
• Create/Edit Lake Objects in DataMind. See Who can do what in the Lake.

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Add the source

1. Open Lake and click Add datasource, or open the New menu in the toolbar above the tree.
2. Choose Clickhouse in the picker.
3. Fill in the General, Connection and Datetime steps as described below.
4. Click Add.

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Connection settings

General step

Name (Mandatory)

• The name the source carries in the Lake.
• At least 3 characters. The field reads Enter name until you type.

Code (Mandatory)

• A short code, at least 2 characters, made of letters and numbers only.
• It becomes the prefix of the table names the source forms. It fills in from Name while you type; edit it to set your own.
• Name and Code cannot be changed after the source is created.

Folder (Optional)

• The Lake folder the source is filed under. Leave it empty to keep the source at the top level.

Connection step: Address

Paste connection string (Optional)

• Click Paste connection string, paste a JDBC URL or a URI, and click Fill.
• Example: jdbc:clickhouse://<server>:8123.
• The string fills Host and Port. A database or a password inside it is not used.

Host (Mandatory)

• The server name or IP address of the ClickHouse server.

Port (Mandatory)

• The port of the server's HTTP interface.
• Default: 8123. With SSL/TLS on, the default is 8443.
• The port follows the SSL/TLS switch while it is still a default. A port you typed yourself is left alone.

The form has no database field: the source reads every database the user can see.

Connection step: Authentication

Username (Mandatory)

• The ClickHouse user the source signs in with.

Password (Mandatory)

• The password of that user.
• After you save, the field reads Stored password with Replace beside it. The password is never shown again.

Connection step: Security

SSL/TLS (Optional)

• Connects over HTTPS instead of HTTP.
• Default: off. The hint reads "SSL/TLS uses HTTPS on port 8443; the port follows the switch while it is a default."

Datetime step

Timezone (Optional)

• The IANA timezone the server writes its datetime values in, for example Europe/Berlin.
• Leave it empty when the server runs in the same timezone as the platform.

Datetime values (Optional)

• Keep as written (wall clock) (default) stores each value exactly as the server shows it.
• The other option converts each value from the source timezone into platform time on load.

Timezones and datetime values explains both settings in full.

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Test and save

1. On the Connection step, click Test connection. The button reads Testing… while it runs.
2. Connection test passed means DataMind reached the server and signed in. A passing test can also show Detected source timezone: with the server's timezone. Connection test failed shows the server's message with a copy button.
3. On Datetime, check the summary: Name, Server, Username and Security.
4. Click Add. Then import its tables.

The test is optional and never saves the source. To edit or duplicate the source later, see Connect a SQL database.

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Questions, answered

Which port do I enter: 8123, 8443 or 9000?

The port of the HTTP interface: 8123 by default, or 8443 for HTTPS. The source does not use the native protocol port, such as 9000, so a test on that port fails.

Why is there no Database field?

The source reads every database the user can see, except the system databases system, information_schema, INFORMATION_SCHEMA and _temporary_and_external_tables. You choose the tables you want when you import. To limit what the source sees, limit the user's grants on the server.

Why do my tables sit under a schema named default?

ClickHouse has no schemas inside a database. The Lake shows each ClickHouse database with a single schema called default, and its tables beneath it.

Do my column types change on load?

Types arrive as the source reports them; a FixedString column arrives as String. See Data types.

Can I send data back to ClickHouse?

Yes. Clickhouse is also offered as a Writeback destination, with the same connection fields. See Add and manage destinations.