pushing id insertion and prefetch primary keys down to Relation#insert

4 files changed, 23 insertions, 12 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
index 5c1ce173c8..756c221fad 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
@@ -272,6 +272,10 @@ module ActiveRecord
         execute "INSERT INTO #{quote_table_name(table_name)} (#{key_list.join(', ')}) VALUES (#{value_list.join(', ')})", 'Fixture Insert'
       end
 
+      def null_insert_value
+        Arel.sql 'DEFAULT'
+      end
+
       def empty_insert_statement_value
         "VALUES(DEFAULT)"
       end
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
index 9ee6b88ab6..ae61d6ce94 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
@@ -336,6 +336,10 @@ module ActiveRecord
         alter_table(table_name, :rename => {column_name.to_s => new_column_name.to_s})
       end
 
+      def null_insert_value
+        Arel.sql 'NULL'
+      end
+
       def empty_insert_statement_value
         "VALUES(NULL)"
       end
diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index df7b22080c..17a64b6e86 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -270,17 +270,9 @@ module ActiveRecord
     # Creates a record with values matching those of the instance attributes
     # and returns its id.
     def create
-      if id.nil? && connection.prefetch_primary_key?(self.class.table_name)
-        self.id = connection.next_sequence_value(self.class.sequence_name)
-      end
-
       attributes_values = arel_attributes_values(!id.nil?)
 
-      new_id = if attributes_values.empty?
-        self.class.unscoped.insert connection.empty_insert_statement_value
-      else
-        self.class.unscoped.insert attributes_values
-      end
+      new_id = self.class.unscoped.insert attributes_values
 
       self.id ||= new_id
 
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 371403f510..8e545f9cad 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -30,15 +30,26 @@ module ActiveRecord
     end
 
     def insert(values)
-      im = arel.compile_insert values
-      im.into @table
-
       primary_key_value = nil
 
       if primary_key && Hash === values
         primary_key_value = values[values.keys.find { |k|
           k.name == primary_key
         }]
+
+        if !primary_key_value && connection.prefetch_primary_key?(klass.table_name)
+          primary_key_value = connection.next_sequence_value(klass.sequence_name)
+          values[klass.arel_table[klass.primary_key]] = primary_key_value
+        end
+      end
+
+      im = arel.create_insert
+      im.into @table
+
+      if values.empty? # empty insert
+        im.values = im.create_values [connection.null_insert_value], []
+      else
+        im.insert values
       end
 
       @klass.connection.insert(