Pass sort keys to Arel as a list rather than an Array (yamldb#119)

Now always generate an array to be a bit clearer, but splat it when used.

Fixes yamldb#115

lib/yaml_db/serialization_helper.rb

@@ -187,12 +187,12 @@ def self.table_column_names(table)
       def self.each_table_page(table, records_per_page=1000)
         total_count = table_record_count(table)
         pages = (total_count.to_f / records_per_page).ceil - 1
-        key = sort_key(table)
+        keys = sort_keys(table)
         boolean_columns = Utils.boolean_columns(table)
         quoted_table_name = Utils.quote_table(table)
 
         (0..pages).to_a.each do |page|
-          query = Arel::Table.new(table).order(key).skip(records_per_page*page).take(records_per_page).project(Arel.sql('*'))
+          query = Arel::Table.new(table).order(*keys).skip(records_per_page*page).take(records_per_page).project(Arel.sql('*'))
           records = ActiveRecord::Base.connection.select_all(query.to_sql)
           records = Utils.convert_booleans(records, boolean_columns)
           yield records
@@ -203,15 +203,15 @@ def self.table_record_count(table)
         ActiveRecord::Base.connection.select_one("SELECT COUNT(*) FROM #{Utils.quote_table(table)}").values.first.to_i
       end
 
-      # Just return the first column as sort key unless the table looks like a
-      # standard HABTM join table, in which case add the second "id column"
-      def self.sort_key(table)
+      # Return the first column as sort key unless the table looks like a
+      # standard has_and_belongs_to_many join table, in which case add the second "ID column"
+      def self.sort_keys(table)
         first_column, second_column = table_column_names(table)
 
         if [first_column, second_column].all? { |name| name =~ /_id$/ }
           [Utils.quote_column(first_column), Utils.quote_column(second_column)]
         else
-          Utils.quote_column(first_column)
+          [Utils.quote_column(first_column)]
         end
       end
     end

spec/yaml_db/serialization_helper_dump_spec.rb

@@ -26,7 +26,7 @@ module SerializationHelper
 
       describe ".each_table_page" do
         before do
-          allow(Dump).to receive(:sort_key)
+          allow(Dump).to receive(:sort_keys)
         end
 
         it "returns all records from the database and returns them when there is only 1 page" do
@@ -72,13 +72,13 @@ module SerializationHelper
         end
       end
 
-      describe ".sort_key" do
+      describe ".sort_keys" do
         before do
           allow(Utils).to receive(:quote_column) { |column| column }
         end
 
         it "returns the first column as sort key" do
-          expect(Dump.sort_key('mytable')).to eq('a')
+          expect(Dump.sort_keys('mytable')).to eq(['a'])
         end
 
         it "returns the combined ids as sort key if the table looks like a HABTM" do
@@ -87,12 +87,12 @@ module SerializationHelper
             double('b_id', :name => 'b_id', :type => :string)
           ])
 
-          expect(Dump.sort_key('mytable')).to eq(['a_id', 'b_id'])
+          expect(Dump.sort_keys('mytable')).to eq(['a_id', 'b_id'])
         end
 
         it "quotes the column name" do
           allow(Utils).to receive(:quote_column).with('a').and_return('`a`')
-          expect(Dump.sort_key('mytable')).to eq('`a`')
+          expect(Dump.sort_keys('mytable')).to eq(['`a`'])
         end
       end
     end