ActiveRecord support to PostgreSQL 9.2 JSON type

This implements the support to encode/decode JSON
data to/from database and creating columns of type
JSON using a native type [1] supported by PostgreSQL
from version 9.2.

[1] http://www.postgresql.org/docs/9.2/static/datatype-json.html

5 files changed, 44 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/column.rb b/activerecord/lib/active_record/connection_adapters/column.rb
index d0237848c7..0390168461 100644
--- a/activerecord/lib/active_record/connection_adapters/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/column.rb
@@ -124,6 +124,7 @@ module ActiveRecord
         when :boolean              then "#{klass}.value_to_boolean(#{var_name})"
         when :hstore               then "#{klass}.string_to_hstore(#{var_name})"
         when :inet, :cidr          then "#{klass}.string_to_cidr(#{var_name})"
+        when :json                 then "#{klass}.string_to_json(#{var_name})"
         else var_name
         end
       end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/cast.rb b/activerecord/lib/active_record/connection_adapters/postgresql/cast.rb
index 20e482dcc2..b59195f98a 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/cast.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/cast.rb
@@ -37,6 +37,22 @@ module ActiveRecord
           end
         end
 
+        def json_to_string(object)
+          if Hash === object
+            ActiveSupport::JSON.encode(object)
+          else
+            object
+          end
+        end
+
+        def string_to_json(string)
+          if String === string
+            ActiveSupport::JSON.decode(string)
+          else
+            string
+          end
+        end
+
         def string_to_cidr(string)
           if string.nil?
             nil
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
index 6657491c06..b8e7687b21 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
@@ -145,6 +145,14 @@ module ActiveRecord
           end
         end
 
+        class Json < Type
+          def type_cast(value)
+            return if value.nil?
+
+            ConnectionAdapters::PostgreSQLColumn.string_to_json value
+          end
+        end
+
         class TypeMap
           def initialize
             @mapping = {}
@@ -244,6 +252,7 @@ module ActiveRecord
         register_type 'polygon', OID::Identity.new
         register_type 'circle', OID::Identity.new
         register_type 'hstore', OID::Hstore.new
+        register_type 'json', OID::Json.new
 
         register_type 'cidr', OID::Cidr.new
         alias_type 'inet', 'cidr'
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
index 1ae7443cde..152258a2f4 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
@@ -22,6 +22,7 @@ module ActiveRecord
           when Hash
             case column.sql_type
             when 'hstore' then super(PostgreSQLColumn.hstore_to_string(value), column)
+            when 'json' then super(PostgreSQLColumn.json_to_string(value), column)
             else super
             end
           when IPAddr
@@ -66,8 +67,11 @@ module ActiveRecord
             return super unless 'bytea' == column.sql_type
             { :value => value, :format => 1 }
           when Hash
-            return super unless 'hstore' == column.sql_type
-            PostgreSQLColumn.hstore_to_string(value)
+            case column.sql_type
+            when 'hstore' then PostgreSQLColumn.hstore_to_string(value)
+            when 'json' then PostgreSQLColumn.json_to_string(value)
+            else super
+            end
           when IPAddr
             return super unless ['inet','cidr'].includes? column.sql_type
             PostgreSQLColumn.cidr_to_string(value)
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 956e83bfd8..c508afb33e 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -106,6 +106,9 @@ module ActiveRecord
           # Hstore
           when /\A'(.*)'::hstore\z/
             $1
+          # JSON
+          when /\A'(.*)'::json\z/
+            $1
           # Object identifier types
           when /\A-?\d+\z/
             $1
@@ -201,6 +204,9 @@ module ActiveRecord
           # UUID type
           when 'uuid'
             :uuid
+        # JSON type
+        when 'json'
+          :json
           # Small and big integer types
           when /^(?:small|big)int$/
             :integer
@@ -267,6 +273,10 @@ module ActiveRecord
         def uuid(name, options = {})
           column(name, 'uuid', options)
         end
+
+        def json(name, options = {})
+          column(name, 'json', options)
+        end
       end
 
       ADAPTER_NAME = 'PostgreSQL'
@@ -290,7 +300,8 @@ module ActiveRecord
         inet:        { name: "inet" },
         cidr:        { name: "cidr" },
         macaddr:     { name: "macaddr" },
-        uuid:        { name: "uuid" }
+        uuid:        { name: "uuid" },
+        json:        { name: "json" }
       }
 
       include Quoting