Patched Relation#build_count_subquery. Fixes #613.

Author: metaskills

CHANGELOG.md

@@ -1,3 +1,10 @@
+## v5.1.3
+
+#### Fixed
+
+* Patched `Relation#build_count_subquery`. Fixes #613.
+
+
 ## v5.1.2
 
 #### Fixed

lib/active_record/connection_adapters/sqlserver/core_ext/calculations.rb

@@ -0,0 +1,39 @@
+require 'active_record/relation'
+require 'active_record/version'
+
+module ActiveRecord
+  module ConnectionAdapters
+    module SQLServer
+      module CoreExt
+        module Calculations
+          private
+
+          def build_count_subquery(relation, column_name, distinct)
+            relation.select_values = [
+              if column_name == :all
+                distinct ? table[Arel.star] : Arel.sql(FinderMethods::ONE_AS_ONE)
+              else
+                column_alias = Arel.sql("count_column")
+                aggregate_column(column_name).as(column_alias)
+              end
+            ]
+
+            subquery = relation.arel.as(Arel.sql("subquery_for_count"))
+            select_value = operation_over_aggregate_column(column_alias || Arel.star, "count", false)
+
+            Arel::SelectManager.new(subquery).project(select_value)
+          end
+        end
+      end
+    end
+  end
+end
+
+ActiveSupport.on_load(:active_record) do
+  if ActiveRecord::VERSION::MAJOR == 5 &&
+     ActiveRecord::VERSION::MINOR == 1 &&
+     ActiveRecord::VERSION::TINY >= 4
+    mod = ActiveRecord::ConnectionAdapters::SQLServer::CoreExt::Calculations
+    ActiveRecord::Relation.prepend(mod)
+  end
+end

lib/active_record/connection_adapters/sqlserver_adapter.rb

@@ -3,6 +3,7 @@
 require 'arel_sqlserver'
 require 'active_record/connection_adapters/abstract_adapter'
 require 'active_record/connection_adapters/sqlserver/core_ext/active_record'
+require 'active_record/connection_adapters/sqlserver/core_ext/calculations'
 require 'active_record/connection_adapters/sqlserver/core_ext/explain'
 require 'active_record/connection_adapters/sqlserver/core_ext/explain_subscriber'
 require 'active_record/connection_adapters/sqlserver/core_ext/attribute_methods'