ClickHouse

ClickHouse is a high-performance, column-oriented SQL data source management system (DBMS) for online analytical processing (OLAP).

Configure the following details for ClickHouse data source:

Register data source
Field	Description
Display name	Enter the data source name to be displayed on the screen.
Hostname	Enter the hostname.
Port	Enter the port number.
Username	Enter the username.
Password	Enter the password.
Port is SSL enabled	Use the toggle switch to enable or disable SSL connection. If enabled, i. The Upload SSL certificate (.pem, .crt, .cert or .cer) link is enabled. ii. Click the Upload SSL certificate (.pem, .crt, .cert or .cer) link. iii. Browse the SSL certificate and upload.
Validate certificate	Use the toggle switch to validate that the SSL certificate that is returned by the host is trusted or not.
Test connection	Click the Test connection link to test the data source connection. If the data source connection is successful, a success message appears.
Catalog name	Enter the name of the catalog. This catalog is automatically associated with your data source.
Create	Click Create to create the data source.

Limitations for SQL statements

For data source-based catalogs the CREATE SCHEMA, CREATE TABLE, DROP SCHEMA, DROP TABLE, DELETE, DROP VIEW, ALTER TABLE, and ALTER SCHEMA statements are not available in the Data Manager UI.

When the fields of data type REAL have 6 digits or more in the decimal part with the digits being predominately zero, the values when queried are rounded off. It is observed that the rounding off occurs differently based on the precision of the values. For example, a decimal number 1.654 when rounded to 3-digits after the decimal point are the same. Another example is 10.890009 and 10.89000. It is noticed that 10.89000 is rounded to 10.89, whereas 10.89009 is not rounded off. This is an inherent issue because of the representational limitations of binary floating point formats. This might have a significant impact when querying involves sorting.