From daab7e59a6196fa2bbab17dc4a88b095a211fc96 Mon Sep 17 00:00:00 2001
From: Sean Griffin <sean@thoughtbot.com>
Date: Sat, 1 Nov 2014 17:15:12 -0600
Subject: Correctly cast calculation results on PG

MySQL reports the column name as `"MAX(developer_id)"`. PG will report
it as `"max"`
---
 .../lib/active_record/connection_adapters/abstract_adapter.rb  |  4 ++++
 .../active_record/connection_adapters/postgresql_adapter.rb    | 10 ++++++++++
 activerecord/lib/active_record/relation/calculations.rb        |  3 ++-
 3 files changed, 16 insertions(+), 1 deletion(-)

(limited to 'activerecord')

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 96b7313234..dc1f3c9457 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -386,6 +386,10 @@ module ActiveRecord
         type_map.lookup(sql_type)
       end
 
+      def column_name_for_operation(operation, node) # :nodoc:
+        node.to_sql
+      end
+
       protected
 
       def initialize_type_map(m) # :nodoc:
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 8e209e1051..e472741660 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -393,6 +393,16 @@ module ActiveRecord
         super(oid)
       end
 
+      def column_name_for_operation(operation, node) # :nodoc:
+        OPERATION_ALIASES.fetch(operation) { operation.downcase }
+      end
+
+      OPERATION_ALIASES = { # :nodoc:
+        "maximum" => "max",
+        "minimum" => "min",
+        "average" => "avg",
+      }
+
       protected
 
         # Returns the version of the connected PostgreSQL server.
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index e20cc0e76d..c8ebb41131 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -253,7 +253,8 @@ module ActiveRecord
 
         select_value = operation_over_aggregate_column(column, operation, distinct)
 
-        column_alias = select_value.alias || select_value.to_sql
+        column_alias = select_value.alias
+        column_alias ||= @klass.connection.column_name_for_operation(operation, select_value)
         relation.select_values = [select_value]
 
         query_builder = relation.arel
-- 
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