Explicitly truncate updated_at and created_at (#132)

* Explicitly truncate updated_at and created_at
* Add truncate to where clause
* Add truncate to checksum_calculated_at

Author: ericaporter

lib/dfe/analytics/services/generic_checksum_calculator.rb

@@ -1,5 +1,4 @@
 require_relative '../shared/service_pattern'
-require_relative '../shared/checksum_query_components'
 
 module DfE
   module Analytics
@@ -8,7 +7,8 @@ module Services
       # and order column in a generic database
       class GenericChecksumCalculator
         include ServicePattern
-        include ChecksumQueryComponents
+
+        WHERE_CLAUSE_ORDER_COLUMNS = %w[CREATED_AT UPDATED_AT].freeze
 
         def initialize(entity, order_column, checksum_calculated_at)
           @entity = entity
@@ -58,6 +58,12 @@ def build_select_and_order_clause(order_column, table_name_sanitized)
 
           [select_clause, order_by_clause]
         end
+
+        def build_where_clause(order_column, table_name_sanitized, checksum_calculated_at_sanitized)
+          return '' unless WHERE_CLAUSE_ORDER_COLUMNS.map(&:downcase).include?(order_column.downcase)
+
+          "WHERE #{table_name_sanitized}.#{order_column.downcase} < #{checksum_calculated_at_sanitized}"
+        end
       end
     end
   end

lib/dfe/analytics/services/postgres_checksum_calculator.rb

@@ -1,5 +1,4 @@
 require_relative '../shared/service_pattern'
-require_relative '../shared/checksum_query_components'
 
 module DfE
   module Analytics
@@ -8,7 +7,8 @@ module Services
       # and order column in a PostgreSQL database
       class PostgresChecksumCalculator
         include ServicePattern
-        include ChecksumQueryComponents
+
+        WHERE_CLAUSE_ORDER_COLUMNS = %w[CREATED_AT UPDATED_AT].freeze
 
         def initialize(entity, order_column, checksum_calculated_at)
           @entity = entity
@@ -55,12 +55,18 @@ def build_select_and_order_clause(order_column, table_name_sanitized)
                         end
           select_clause = case order_column
                           when 'UPDATED_AT', 'CREATED_AT'
-                            "#{table_name_sanitized}.#{order_column.downcase} AS \"#{order_alias}\""
+                            "DATE_TRUNC('milliseconds', #{table_name_sanitized}.#{order_column.downcase}) AS \"#{order_alias}\""
                           else
                             "#{table_name_sanitized}.id::TEXT AS \"#{order_alias}\""
                           end
           [select_clause, order_alias]
         end
+
+        def build_where_clause(order_column, table_name_sanitized, checksum_calculated_at_sanitized)
+          return '' unless WHERE_CLAUSE_ORDER_COLUMNS.map(&:downcase).include?(order_column.downcase)
+
+          "WHERE DATE_TRUNC('milliseconds', #{table_name_sanitized}.#{order_column.downcase}) < DATE_TRUNC('milliseconds', '#{checksum_calculated_at_sanitized}')"
+        end
       end
     end
   end

lib/dfe/analytics/shared/checksum_query_components.rb

@@ -215,5 +215,17 @@
           })])
       end
     end
+
+    it 'orders records by updated_at truncated to milliseconds' do
+      time_base = Time.zone.now.beginning_of_minute
+      Candidate.create(email_address: 'first@example.com', updated_at: time_base + 0.001.seconds)
+      Candidate.create(email_address: 'second@example.com', updated_at: time_base + 0.005.seconds)
+
+      described_class.call(entity_name: candidate_entity, entity_type: entity_type, entity_tag: nil)
+
+      ordered_candidates = Candidate.order(:updated_at).pluck(:email_address)
+
+      expect(ordered_candidates).to eq(['first@example.com', 'second@example.com'])
+    end
   end
 end