1 files changed, 21 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/type/hash_lookup_type_map.rb b/activerecord/lib/active_record/connection_adapters/type/hash_lookup_type_map.rb
new file mode 100644
index 0000000000..8503d3ea1b
--- /dev/null
+++ b/activerecord/lib/active_record/connection_adapters/type/hash_lookup_type_map.rb
@@ -0,0 +1,21 @@
+module ActiveRecord
+  module ConnectionAdapters
+    module Type
+      class HashLookupTypeMap < TypeMap # :nodoc:
+        delegate :key?, to: :@mapping
+
+        def lookup(type)
+          @mapping.fetch(type, proc { default_value }).call(type)
+        end
+
+        def fetch(type, &block)
+          @mapping.fetch(type, block).call(type)
+        end
+
+        def alias_type(type, alias_type)
+          register_type(type) { lookup(alias_type) }
+        end
+      end
+    end
+  end
+end