fix: Support time zone when serializing DateTimes

lib/click_house/type/date_time64_type.rb

@@ -32,8 +32,12 @@ def cast(value, precision = 0, tz = nil)
         end
       end
 
-      def serialize(value, precision = 3, _tz = nil)
-        value.strftime(SERIALIZE_FORMATS.fetch(precision))
+      def serialize(value, precision = 3, tz = nil)
+        if tz
+          value.in_time_zone(Time.find_zone(tz)).strftime(SERIALIZE_FORMATS.fetch(precision))
+        else
+          value.strftime(SERIALIZE_FORMATS.fetch(precision))
+        end
       end
     end
   end

lib/click_house/type/date_time_type.rb

@@ -13,8 +13,12 @@ def cast(value, tz = nil)
         end
       end
 
-      def serialize(value, *)
-        value.strftime(FORMAT)
+      def serialize(value, tz = nil)
+        if tz
+          value.in_time_zone(Time.find_zone(tz)).strftime(FORMAT)
+        else
+          value.strftime(FORMAT)
+        end
       end
     end
   end

spec/click_house/type/date_time64_spec.rb

@@ -1,5 +1,5 @@
 RSpec.describe ClickHouse::Type::DateTime64Type do
-  let(:precisions) do 
+  let(:precisions) do
     (0..9).to_a
   end
 
@@ -9,11 +9,24 @@
     end
 
     it 'works' do
-      precisions.each do |precision|        
+      precisions.each do |precision|
         tail = "." + "0" * precision if precision > 0
         expect(subject.serialize(time, precision)).to eq("2019-01-01 09:05:06#{tail}")
       end
     end
+
+    context 'when zone exists' do
+      let(:time) do
+        Time.new(2019, 1, 1, 9, 5, 6, Time.find_zone('UTC'))
+      end
+
+      it 'works' do
+        precisions.each do |precision|
+          tail = "." + "0" * precision if precision > 0
+          expect(subject.serialize(time, precision, 'Europe/Kyiv')).to eq("2019-01-01 11:05:06#{tail}")
+        end
+      end
+    end
   end
 
   describe '#cast' do

spec/click_house/type/date_time_type_spec.rb

@@ -7,6 +7,16 @@
     it 'works' do
       expect(subject.serialize(time)).to eq('2019-01-01 09:05:06')
     end
+
+    context 'when zone exists' do
+      let(:time) do
+        Time.new(2019, 1, 1, 9, 5, 6, Time.find_zone('UTC'))
+      end
+
+      it 'works' do
+        expect(subject.serialize(time, 'Europe/Kyiv')).to eq('2019-01-01 11:05:06')
+      end
+    end
   end
 
   describe '#cast' do