fix: Support time zone when serializing DateTimes

Previously a DateTime being serialized would ignore the timezone, effectively assuming the timezone of the value was the same as the column.

Instead, the timezone is now taken into account so the time can be given in any timezone and it will be converted to the timezone of the column.

Author: njakobsen

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