This article covers how to install ClickHouse on Ubuntu. Basically, ClickHouse is an open-source analytics database developed for big data use cases.
Install of ClickHouse on Ubuntu involves a series of steps that includes adjusting the configuration file to enable listening over other IP address and remote access.
Column-oriented databases store records in blocks grouped by columns instead of rows.
By not loading data for columns absent in the query, column-oriented databases spend less time reading data while completing queries.
As a result, these databases can compute and return results much faster than traditional row-based systems for certain workloads, such as OLAP.
Online Analytics Processing (OLAP) systems allow for organizing large amounts of data and performing complex queries.
They are capable of managing petabytes of data and returning query results quickly.
In this way, OLAP is useful for work in areas like data science and business analytics.
Aggregation queries are queries that operate on a set of values and return single output values.
In analytics databases, these queries are run frequently and are well optimized by the database.
Some aggregate functions supported by ClickHouse are:
1. count: returns the count of rows matching the conditions specified.
2. sum: returns the sum of selected column values.
3. avg: returns the average of selected column values.
Some ClickHouse-specific aggregate functions include:
1. uniq: returns an approximate number of distinct rows matched.
2. topK: returns an array of the most frequent values of a specific column using an approximation algorithm.
You can set up a ClickHouse database instance on your server and create a database and table, add data, perform queries, and delete the database.
You can start, stop, and check the ClickHouse service with a few commands.
To start the clickhouse-server, use:
$ sudo systemctl start clickhouse-server
The output does not return a confirmation.
To check the ClickHouse service status, enter:
$ sudo systemctl status clickhouse-server
To stop the ClickHouse server, run this command:
$ sudo systemctl stop clickhouse-server
To enable ClickHouse on boot:
$ sudo systemctl enable clickhouse-server
To start working with ClickHouse databases, launch the ClickHouse client.
When you start a session, the procedure is similar to other SQL management systems.
To start the client, use the command: