Added support for ClickHouse

README.md

@@ -566,6 +566,7 @@ data_sources:
 - [Apache Ignite](#apache-ignite)
 - [Apache Spark](#apache-spark)
 - [Cassandra](#cassandra)
+- [ClickHouse](#clickhouse)
 - [Druid](#druid)
 - [Elasticsearch](#elasticsearch)
 - [Google BigQuery](#google-bigquery)
@@ -713,6 +714,19 @@ data_sources:
     url: cassandra://user:password@hostname:9042/keyspace
 ```
 
+### ClickHouse
+
+Add [ClickHouse Ruby driver](https://github.com/shlima/click_house) to your Gemfile and set:
+```yml
+data_sources:
+  my_source:
+    adapter: clickhouse
+    url: http://user:password@hostname:8123/database
+
+    # optional settings
+    ssl_verify: true # false by default
+```
+
 ### Druid
 
 Enable [SQL support](http://druid.io/docs/latest/querying/sql.html#configuration) on the broker and set:

lib/blazer.rb

@@ -15,6 +15,7 @@
 require "blazer/adapters/athena_adapter"
 require "blazer/adapters/bigquery_adapter"
 require "blazer/adapters/cassandra_adapter"
+require "blazer/adapters/clickhouse_adapter"
 require "blazer/adapters/drill_adapter"
 require "blazer/adapters/druid_adapter"
 require "blazer/adapters/elasticsearch_adapter"
@@ -254,6 +255,7 @@ def self.archive_queries
 Blazer.register_adapter "athena", Blazer::Adapters::AthenaAdapter
 Blazer.register_adapter "bigquery", Blazer::Adapters::BigQueryAdapter
 Blazer.register_adapter "cassandra", Blazer::Adapters::CassandraAdapter
+Blazer.register_adapter "clickhouse", Blazer::Adapters::ClickhouseAdapter
 Blazer.register_adapter "drill", Blazer::Adapters::DrillAdapter
 Blazer.register_adapter "druid", Blazer::Adapters::DruidAdapter
 Blazer.register_adapter "elasticsearch", Blazer::Adapters::ElasticsearchAdapter

lib/blazer/adapters/clickhouse_adapter.rb

@@ -0,0 +1,84 @@
+module Blazer
+  module Adapters
+    class ClickhouseAdapter < BaseAdapter
+      DATE_TIME_TYPES = ["DateTime", "DateTime(%s)", "DateTime64(%d, %s)"].freeze
+
+      def run_statement(statement, _comment)
+        columns = []
+        rows = []
+        error = nil
+
+        begin
+          result = connection.select_all(statement)
+          unless result.data.blank?
+            date_time_columns = result.meta
+                                      .select { |column| column["type"].in?(DATE_TIME_TYPES) }
+                                      .map { |column| column["name"] }
+            columns = result.data.first.keys
+            rows = result.data.map { |row| convert_time_columns(row, date_time_columns).values }
+          end
+        rescue => e
+          error = e.message
+        end
+
+        [columns, rows, error]
+      end
+
+      def tables
+        connection.tables
+      end
+
+      def schema
+        statement = <<-SQL
+          SELECT table, name, type
+          FROM system.columns
+          WHERE database = currentDatabase()
+          ORDER BY table, position
+        SQL
+
+        response = connection.post(query: { query: statement, default_format: "CSV" })
+        response.body
+                .group_by { |row| row[0] }
+                .transform_values { |columns| columns.map { |c| { name: c[1], data_type: c[2] } } }
+                .map { |table, columns| { schema: "public", table: table, columns: columns } }
+      end
+
+      def preview_statement
+        "SELECT * FROM {table} LIMIT 10"
+      end
+
+      def explain(statement)
+        connection.explain(statement)
+      end
+
+      protected
+
+      def connection
+        @connection ||= ClickHouse::Connection.new(config)
+      end
+
+      def config
+        @config ||= begin
+          uri = URI.parse(settings["url"])
+          options = {
+            scheme: uri.scheme,
+            host: uri.host,
+            port: uri.port,
+            username: uri.user,
+            password: uri.password,
+            database: uri.path.sub(/\A\//, ""),
+            ssl_verify: settings.fetch("ssl_verify", false)
+          }.compact
+          ClickHouse::Config.new(**options)
+        end
+      end
+
+      def convert_time_columns(row, date_time_columns)
+        time_values = row.slice(*date_time_columns).transform_values!(&:to_time)
+        row.merge(time_values)
+      rescue NoMethodError
+        row
+      end
+    end
+  end
+end