A Ruby database driver for ClickHouse (also Clickhouse CLI and web GUI included).
ClickHouse manages extremely large volumes of data in a stable and sustainable manner. It currently powers Yandex.Metrica, world’s second largest web analytics platform, with over 13 trillion database records and over 20 billion events a day, generating customized reports on-the-fly, directly from non-aggregated data. This system was successfully implemented at CERN’s LHCb experiment to store and process metadata on 10bn events with over 1000 attributes per event registered in 2011.
On June 15th 2016, Yandex open-sourced their awesome project giving the community a powerful asset which can compete with the big players like Google BigQuery and Amazon Redshift with an important advantage: the client can use ClickHouse in its infrastructure and does not have to pay for the cloud (read more).
Why use the HTTP interface and not the TCP interface?
Well, the developers of ClickHouse themselves discourage using the TCP interface.
TCP transport is more specific, we don't want to expose details. Despite we have full compatibility of protocol of different versions of client and server, we want to keep the ability to "break" it for very old clients. And that protocol is not too clean to make a specification.
Why use the JSONCompact format and not the native format?
Despite of it being the most efficient format, using the native format is also discouraged by the ClickHouse developers.
The most efficient format. Data is written and read by blocks in binary format. For each block, the number of rows, number of columns, column names and types, and parts of columns in this block are recorded one after another. In other words, this format is "columnar" - it doesn't convert columns to rows. This is the format used in the native interface for interaction between servers, for using the command-line client, and for C++ clients.
You can use this format to quickly generate dumps that can only be read by the ClickHouse DBMS. It doesn't make sense to work with this format yourself.
Run the following command to install
$ gem install "clickhouse"
Require the Clickhouse gem.
Setup the logging output.
require "logger" Clickhouse.logger = Logger.new(STDOUT)
Establish the connection with the ClickHouse server (using the default config).
Clickhouse.establish_connection => true
List databases and tables.
Clickhouse.connection.databases I, [2016-10-17T22:54:26.587401 #81829] INFO -- : SQL (64.0ms) SHOW DATABASES; => ["default", "system"] Clickhouse.connection.tables I, [2016-10-17T22:54:51.454012 #81829] INFO -- : SQL (61.7ms) SHOW TABLES; => 
Clickhouse.connection.create_table("events") do |t| t.fixed_string :id, 16 t.uint16 :year t.date :date t.date_time :time t.string :event t.uint32 :user_id t.float32 :revenue t.engine "MergeTree(date, (year, date), 8192)" end => true Clickhouse.connection.query "DESCRIBE TABLE events" # or Clickhouse.connection.describe_table "events" => #<Clickhouse::Connection::Query::ResultSet:0x007fa9ac137010 @names=["name", "type", "default_type", "default_expression"], @rows= [["id", "FixedString(16)", nil, nil], ["year", "UInt16", nil, nil], ["date", "Date", nil, nil], ["time", "DateTime", nil, nil], ["event", "String", nil, nil], ["user_id", "UInt32", nil, nil], ["revenue", "Float32", nil, nil]], @types=["String", "String", "String", "String"]>
Check if table exists.
Clickhouse.connection.exists_table("events") => true
Clickhouse.connection.insert_rows(events, :names => %w(id year date time event user_id revenue)) do |rows| rows << [ "d91d1c90", 2016, "2016-10-17", "2016-10-17 23:14:28", "click", 1982, 0.18 ] rows << [ "d91d2294", 2016, "2016-10-17", "2016-10-17 23:14:41", "click", 1947, 0.203 ] end => true
Clickhouse.connection.count :from => "events" I, [2016-10-17T23:19:45.592602 #82196] INFO -- : SQL (65.4ms) SELECT COUNT(*) FROM events; => 2 Clickhouse.connection.select_row :select => "COUNT(*), year, date, avg(revenue)", :from => "events", :group => "year, date" I, [2016-10-17T23:22:47.340232 #82196] INFO -- : SQL (67.7ms) SELECT COUNT(*), year, date, avg(revenue) FROM events GROUP BY year, date; => [2, 2016, #<Date: 2016-10-17 ((2457679j,0s,0n),+0s,2299161j)>, 0.1915000081062317]
Connecting to a cluster
To connect to a cluster you only need to specify the URLs of the cluster servers in
:urls of the configuration and that is it! The API of using Clickhouse stays the same.
Clickhouse.establish_connection urls: %w(http://192.168.99.100:32809 http://192.168.99.100:32812 http://192.168.99.100:32815) => true Clickhouse.connection.tables I, [2016-10-21T11:56:47.375772 #63374] INFO -- : SQL (6.2ms) SHOW TABLES; => ["events"]
In case of a connection dropping out, Clickhouse will retry the request with another connection. The failed connection will also be removed from the connection pool.
Clickhouse.establish_connection urls: %w(http://192.168.99.100:32809 http://192.168.99.100:1 http://192.168.99.100:32815) => true Clickhouse.connection.pond.available.collect(&:url) => ["http://192.168.99.100:1", "http://192.168.99.100:32815", "http://192.168.99.100:32809"] Clickhouse.connection.tables I, [2016-10-21T12:11:55.974573 #63527] INFO -- : SQL (7.1ms) SHOW TABLES; => ["events"] Clickhouse.connection.pond.available.collect(&:url) => ["http://192.168.99.100:32809", "http://192.168.99.100:32815"]
If all the connections failed, it will just return
Check out the tests
To see what more the
Clickhouse gem has to offer, please take a look at the unit tests ( test/unit/connection/test_query.rb for instance).
Using the Sinatra-based browser GUI and Thor-based CLI
Clickhouse v0.1.8, the gem is provided with both a Sinatra-based GUI and a Thor-based CLI. Starting either of them is very easy:
clickhouse s localhost:8123- (the
sstands for server as we know from
clickhouse c localhost:8123- (the
cstands for console as we know from
Multiple connections should be passed comma separated:
clickhouse s https://myserver.com:8123,https://myserver.com:8124
clickhouse help to:
$ clickhouse help server Usage: clickhouse server [HOSTS] Options: -p, [--port=N] # Default: 1982 -u, [--username=USERNAME] -P, [--password=PASSWORD] Start a Sinatra server as ClickHouse client (HOSTS should be comma separated URIs)
Using the console
As you probably already noticed, the
Clickhouse repo is provided with a
script/console file which you can use for development / testing purposes. Please note that you need to have a ClickHouse server running.
Running a ClickHouse server on your Mac or Windows computer
Despite that the ClickHouse build is not intended to work on Mac OS X or Windows (only x86_64 with SSE 4.2 is supported), you can still run a ClickHouse server instance on both the operating systems using the ClickHouse Server Docker Image hosted on [https://hub.docker.com/](Docker Hub).
The installation process is just a matter of two simple steps:
- Download and install Kitematic (Docker Toolbox) on your computer
- Install the clickhouse-server container using Kitematic
Et voilà! Your ClickHouse server instance is up and running locally. Please make sure to use the proper IP address and port to connect with. You can find it at the container details within Kitematic (it is the
Access URL corresponded with the
8123/tcp Docker port).
$ script/console Loading Clickhouse development environment (0.1.1)  pry(main)> connect! host: "192.168.99.100", port: 32770 => true  pry(main)> conn.databases I, [2016-10-19T20:54:53.081388 #29847] INFO -- : SQL (3.1ms) SHOW DATABASES; => ["default", "system"]  pry(main)>
Run the following command for testing:
You can also run a single test file:
$ ruby test/unit/connection/test_query.rb
For support, remarks and requests, please mail me at firstname.lastname@example.org.
Copyright (c) 2016 Paul Engel, released under the MIT license
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