Enable JSON type in clickhouse

.docker/clickhouse/users.xml

@@ -4,6 +4,7 @@
   <profiles>
     <default>
       <load_balancing>random</load_balancing>
+      <allow_experimental_object_type>1</allow_experimental_object_type>
     </default>
   </profiles>
 

README.md

@@ -199,6 +199,9 @@ false`. The default integer is `UInt32`
 | UInt64          |          0 to 18446744073709551615           |            5,6,7,8 |
 | UInt256         |                   0 to ...                   |                 8+ |
 | Array           |                     ...                      |                ... |
+| Json*           |                     ...                      |                ... |
+
+* **Note**: using the JSON type requires that `allow_experimental_object_type = 1` is [set in ClickHouse settings](https://clickhouse.com/docs/en/sql-reference/data-types/json).
 
 Example:
 

lib/active_record/connection_adapters/clickhouse_adapter.rb

@@ -100,6 +100,8 @@ class ClickhouseAdapter < AbstractAdapter
         boolean: { name: 'Bool' },
         uuid: { name: 'UUID' },
 
+        json: { name: 'Object(\'json\')' },
+
         enum8: { name: 'Enum8' },
         enum16: { name: 'Enum16' },
 
@@ -207,6 +209,7 @@ def initialize_type_map(m) # :nodoc:
 
           m.register_type %r(bool)i, ActiveModel::Type::Boolean.new
           m.register_type %r{uuid}i, Clickhouse::OID::Uuid.new
+          m.register_type %r{Object\('json'\)}i, Type::Json.new
           # register_class_with_limit m, %r(Array), Clickhouse::OID::Array
           m.register_type(%r(Array)) do |sql_type|
             Clickhouse::OID::Array.new(sql_type)

spec/fixtures/migrations/add_sample_data/1_create_sample_table.rb

@@ -12,6 +12,7 @@ def up
       t.string :byte_array, null: true
       t.uuid :relation_uuid
       t.decimal :decimal_value, precision: 38, scale: 16, null: true
+      t.json :json_value, null: false, default: {}
     end
   end
 end

spec/single/model_spec.rb

@@ -154,6 +154,28 @@ class ModelPk < ActiveRecord::Base
       end
     end
 
+    describe 'JSON column type' do
+      let(:json) { { 'key' => 'value' } }
+      let!(:record1) { Model.create!(event_name: 'some event', json_value: json) }
+
+      it 'is mapped to :json' do
+        type = Model.columns_hash['json_value'].type
+        expect(type).to eq(:json)
+      end
+
+      it 'keeps JSON value' do
+        expect(Model.first.json_value).to eq(json)
+      end
+
+      context 'when the JSON column is complex' do
+        let(:json) { { 'key' => { 'nested_key' => 'value', 'another_key' => ['something'] } } }
+
+        it 'keeps JSON value' do
+          expect(Model.first.json_value).to eq(json)
+        end
+      end
+    end
+
     describe 'UUID column type' do
       let(:random_uuid) { SecureRandom.uuid }
       let!(:record1) do