ClickHouse Connection

It is used for connection to the ClickHouse database.

Connection Parameters

The following parameters are set during the connection setup:

  • Caption contains the connection name set by a user.
  • Connection string represents the string of the following kind: host[:port][:database]. It is set in a separate window that can be called both by clicking on button, and by entering the parameters manually. Port and database parameters are optional. By default, port 9000, default database.
  • Test: test of the specified connection settings.
  • Username: login of the DB user. By default, default.
  • Password: password of the DB user. The password is not available by default.
  • SSL settings: button enables to call the dialog of connection parameters setup via secure connection:
    • Use SSL: when this checkbox is selected, the data is transferred via the cryptographic SSL/TLS protocol.
    • CA certificate: path to the file with the root certificate.
    • User certificate: path to the file with the client certificate.
    • Private key: path to the file with the private key.
    • Private key password: private key password. It is null by default.
  • Use local time zone provides conversion from the local time to UTC and vice versa for the columns of the DateTime type. This option is enabled by default.
  • Data compression method: Without compression (it is used by default) and LZ4 options are available.
  • Show system tables: when selecting this checkbox in the import wizard that uses this connection, the system DB tables available to a user become visible.
  • Quote names: if the database objects names (for example, names of tables, fields) contain spaces or reserved characters, it is required to use framing characters fixing the name start and end.
  • Configure quotes represents the information field that enables to define which framing characters are used for connection to this DB. Double quotes are used for ClickHouse.
  • Do not use DBMS client is not available as the inbox driver is always used to connect to ClickHouse.
  • Comment: it is possible to provide any reference connection data in this form.

Note:

  • Connection pool is not used.
  • When exporting data to the new table, the Log engine table is created.
  • In connection with the ClickHouse DB restrictions:
    • Transactions are not supported.
    • Dates from 1970 to 2106 are supported.
    • Update of the current records in the table is not supported.
    • Deletion by key is available only for the tables with the MergeTree engines.

Important: Data mutation operations are not atomic in the MergeTree tables (for more details, see Mutations). As mutations are used during the export operation with deletion by key, the export node activation does not provide termination of the records deletion process. Duration of the mutation performed by a user is not controlled. Thus, request for data sampling set just after execution of the export node with deletion by key can return the old records. It is required to take this ClickHouse DB feature into account when designing systems.

Compatibility

DB versions of ClickHouse 19.1 and higher.

See also:

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