Correctly dump composite primary key

Example:

    create_table :barcodes, primary_key: ["region", "code"] do |t|
      t.string :region
      t.integer :code
    end

1 files changed, 2 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 24fc67938d..452102a357 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -369,10 +369,9 @@ module ActiveRecord
         end
       end
 
-      def primary_key(table_name) #:nodoc:
+      def primary_keys(table_name) # :nodoc:
         pks = table_structure(table_name).select { |f| f['pk'] > 0 }
-        return nil unless pks.count == 1
-        pks[0]['name']
+        pks.sort_by { |f| f['pk'] }.map { |f| f['name'] }
       end
 
       def remove_index(table_name, options = {}) #:nodoc: