Don't store all aliases to a table

The aliases property of a table is never used other than for equality. However,
the aliases that have been created for a table aren't really something that
should affect whether a table is considered to be the same table or not. This
removal does not appear to have any affect within Active Record or within Arel.

lib/arel/table.rb

@@ -6,15 +6,14 @@ class Table
     @engine = nil
     class << self; attr_accessor :engine; end
 
-    attr_accessor :name, :aliases, :table_alias
+    attr_accessor :name, :table_alias
 
     # TableAlias and Table both have a #table_name which is the name of the underlying table
     alias :table_name :name
 
     def initialize(name, as: nil, type_caster: nil)
       @name    = name.to_s
       @columns = nil
-      @aliases = []
       @type_caster = type_caster
 
       # Sometime AR sends an :as parameter to table, to let the table know
@@ -27,9 +26,7 @@ def initialize(name, as: nil, type_caster: nil)
     end
 
     def alias name = "#{self.name}_2"
-      Nodes::TableAlias.new(self, name).tap do |node|
-        @aliases << node
-      end
+      Nodes::TableAlias.new(self, name)
     end
 
     def from
@@ -94,7 +91,6 @@ def hash
     def eql? other
       self.class == other.class &&
         self.name == other.name &&
-        self.aliases == other.aliases &&
         self.table_alias == other.table_alias
     end
     alias :== :eql?

test/test_table.rb

@@ -110,10 +110,7 @@ module Arel
 
     describe 'alias' do
       it 'should create a node that proxies to a table' do
-        @relation.aliases.must_equal []
-
         node = @relation.alias
-        @relation.aliases.must_equal [node]
         node.name.must_equal 'users_2'
         node[:id].relation.must_equal node
       end
@@ -191,22 +188,18 @@ module Arel
     describe 'equality' do
       it 'is equal with equal ivars' do
         relation1 = Table.new(:users)
-        relation1.aliases     = %w[a b c]
         relation1.table_alias = 'zomg'
         relation2 = Table.new(:users)
-        relation2.aliases     = %w[a b c]
         relation2.table_alias = 'zomg'
         array = [relation1, relation2]
         assert_equal 1, array.uniq.size
       end
 
       it 'is not equal with different ivars' do
         relation1 = Table.new(:users)
-        relation1.aliases     = %w[a b c]
         relation1.table_alias = 'zomg'
         relation2 = Table.new(:users)
-        relation2.aliases     = %w[x y z]
-        relation2.table_alias = 'zomg'
+        relation2.table_alias = 'zomg2'
         array = [relation1, relation2]
         assert_equal 2, array.uniq.size
       end