stop using distinct on for the unique id queries. [#6450 state:resolved]

2 files changed, 3 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index acc3e9c5e3..66ca831d6c 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -935,7 +935,7 @@ module ActiveRecord
 
         # Return a DISTINCT ON() clause that's distinct on the columns we want but includes
         # all the required columns for the ORDER BY to work properly.
-        sql = "DISTINCT ON (#{columns}) #{columns}, "
+        sql = "DISTINCT #{columns}, "
         sql << order_columns * ', '
       end
 
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index aae257a0e7..a3d4b7f45a 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -246,6 +246,8 @@ module ActiveRecord
       orders = relation.order_values
       values = @klass.connection.distinct("#{@klass.connection.quote_table_name table_name}.#{primary_key}", orders)
 
+      relation = relation.dup
+
       ids_array = relation.select(values).collect {|row| row[primary_key]}
       ids_array.empty? ? raise(ThrowResult) : table[primary_key].in(ids_array)
     end