1 files changed, 16 insertions, 3 deletions
diff --git a/lib/gitlab/pagination/keyset/in_operator_optimization/column_data.rb b/lib/gitlab/pagination/keyset/in_operator_optimization/column_data.rb
index 3f620f74eca..93b28661bb0 100644
--- a/lib/gitlab/pagination/keyset/in_operator_optimization/column_data.rb
+++ b/lib/gitlab/pagination/keyset/in_operator_optimization/column_data.rb
@@ -4,23 +4,35 @@ module Gitlab
   module Pagination
     module Keyset
       module InOperatorOptimization
+        # This class is used for wrapping an Arel column with
+        # convenient helper methods in order to make the query
+        # building for the InOperatorOptimization a bit cleaner.
         class ColumnData
           attr_reader :original_column_name, :as, :arel_table
 
-          def initialize(original_column_name, as, arel_table)
-            @original_column_name = original_column_name.to_s
+          # column - name of the DB column
+          # as - custom alias for the column
+          # arel_table - relation where the column is located
+          def initialize(column, as, arel_table)
+            @original_column_name = column
             @as = as.to_s
             @arel_table = arel_table
           end
 
+          # Generates: `issues.name AS my_alias`
           def projection
             arel_column.as(as)
           end
 
+          # Generates: issues.name`
           def arel_column
             arel_table[original_column_name]
           end
 
+          # overridden in OrderByColumnData class
+          alias_method :column_expression, :arel_column
+
+          # Generates: `issues.my_alias`
           def arel_column_as
             arel_table[as]
           end
@@ -29,8 +41,9 @@ module Gitlab
             "#{arel_table.name}_#{original_column_name}_array"
           end
 
+          # Generates: SELECT ARRAY_AGG(...) AS issues_name_array
           def array_aggregated_column
-            Arel::Nodes::NamedFunction.new('ARRAY_AGG', [arel_column]).as(array_aggregated_column_name)
+            Arel::Nodes::NamedFunction.new('ARRAY_AGG', [column_expression]).as(array_aggregated_column_name)
           end
         end
       end