Using ClickHouse from Scratch¶
ClickHouse is a column-based database oriented to online analysis and processing. It supports SQL query and provides good query performance. The aggregation analysis and query performance based on large and wide tables is excellent, which is one order of magnitude faster than other analytical databases.
Prerequisites¶
You have installed the client, for example, in the /opt/hadoopclient directory. The client directory in the following operations is only an example. Change it to the actual installation directory. Before using the client, download and update the client configuration file, and ensure that the active management node of Manager is available.
Procedure¶
Log in to the node where the client is installed as the client installation user.
Run the following command to go to the client installation directory:
cd /opt/hadoopclient
Run the following command to configure environment variables:
source bigdata_env
If Kerberos authentication is enabled for the current cluster, run the following command to authenticate the current user. The current user must have the permission to create ClickHouse tables. For details about how to bind a role to the user, see ClickHouse User and Permission Management. If Kerberos authentication is disabled for the current cluster, skip this step.
kinit Component service user
Example: kinit clickhouseuser
Run the client command of the ClickHouse component.
Run the clickhouse -h command to view the command help of ClickHouse.
The command output is as follows:
Use one of the following commands: clickhouse local [args] clickhouse client [args] clickhouse benchmark [args] clickhouse server [args] clickhouse performance-test [args] clickhouse extract-from-config [args] clickhouse compressor [args] clickhouse format [args] clickhouse copier [args] clickhouse obfuscator [args] ...
The following table describes the parameters when the clickhouse client command is used to connect to the ClickHouse server.
Table 1 Parameters of the clickhouse client command¶ Parameter
Description
--host
Host name of the server. The default value is localhost. You can use the host name or IP address of the node where the ClickHouse instance is located.
--port
Port for connection.
If the SSL security connection is used, the default port number is 9440, the parameter --secure must be carried. For details about the port number, search for the tcp_port_secure parameter in the ClickHouseServer instance configuration.
If non-SSL security connection is used, the default port number is 9000, the parameter --secure does not need to be carried. For details about the port number, search for the tcp_port parameter in the ClickHouseServer instance configuration.
--user
Username.
You can create the user on Manager and bind a role to the user. For details, see ClickHouse User and Permission Management.
If Kerberos authentication is enabled for the current cluster and the user authentication is successful, you do not need to carry the --user and --password parameters when logging in to the client as the authenticated user. You must create a user with this name on Manager because there is no default user in the Kerberos cluster scenario.
If Kerberos authentication is not enabled for the current cluster, you can specify a user and its password created on Manager when logging in to the client. If the user is used for the first time, you need to log in to Manager to change the password. If the user and password parameters are not carried, user default is used for login by default.
--password
Password. The default password is an empty string. This parameter is used together with the --user parameter. You can set a password when creating a user on Manager.
--query
Query to process when using non-interactive mode.
--database
Current default database. The default value is default, which is the default configuration on the server.
--multiline
If this parameter is specified, multiline queries are allowed. (Enter only indicates line feed and does not indicate that the query statement is complete.)
--multiquery
If this parameter is specified, multiple queries separated with semicolons (;) can be processed. This parameter is valid only in non-interactive mode.
--format
Specified default format used to output the result.
--vertical
If this parameter is specified, the result is output in vertical format by default. In this format, each value is printed on a separate line, which helps to display a wide table.
--time
If this parameter is specified, the query execution time is printed to stderr in non-interactive mode.
--stacktrace
If this parameter is specified, stack trace information will be printed when an exception occurs.
--config-file
Name of the configuration file.
--secure
If this parameter is specified, the server will be connected in SSL mode.
--history_file
Path of files that record command history.
--param_<name>
Query with parameters. Pass values from the client to the server.
Using SSL for login when Kerberos authentication is disabled for the current cluster:
clickhouse client --host IP address of the ClickHouse instance --user Username --password Password --port 9440 --secure
Using SSL for login when Kerberos authentication is enabled for the current cluster:
You must create a user on Manager because there is no default user. For details, see ClickHouse User and Permission Management.
After the user authentication is successful, you do not need to carry the --user and --password parameters when logging in to the client as the authenticated user.
clickhouse client --host IP address of the ClickHouse instance --port 9440 --secure
Note
You can log in to FusionInsight Manager and choose Cluster > Services > ClickHouse > Instance to obtain the service IP address of the ClickHouseServer instance.