Extract aliasing code from JoinDependency and JoinAssociation into a separate AliasTracker class. This can then be used by ThroughAssociationScope as well.

1 files changed, 68 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/associations/alias_tracker.rb b/activerecord/lib/active_record/associations/alias_tracker.rb
new file mode 100644
index 0000000000..f48efabec2
--- /dev/null
+++ b/activerecord/lib/active_record/associations/alias_tracker.rb
@@ -0,0 +1,68 @@
+require 'active_support/core_ext/string/conversions'
+
+module ActiveRecord
+  module Associations
+    # Keeps track of table aliases for ActiveRecord::Associations::ClassMethods::JoinDependency
+    class AliasTracker # :nodoc:
+      # other_sql is some other sql which might conflict with the aliases we assign here. Therefore
+      # we store other_sql so that we can scan it before assigning a specific name.
+      def initialize(other_sql)
+        @aliases   = Hash.new
+        @other_sql = other_sql.to_s.downcase
+      end
+      
+      def aliased_name_for(table_name, aliased_name = nil)
+        aliased_name ||= table_name
+        
+        initialize_count_for(table_name) if @aliases[table_name].nil?
+
+        if @aliases[table_name].zero?
+          # If it's zero, we can have our table_name
+          @aliases[table_name] = 1
+          table_name
+        else
+          # Otherwise, we need to use an alias
+          aliased_name = connection.table_alias_for(aliased_name)
+          
+          initialize_count_for(aliased_name) if @aliases[aliased_name].nil?
+          
+          # Update the count
+          @aliases[aliased_name] += 1
+          
+          if @aliases[aliased_name] > 1
+            "#{truncate(aliased_name)}_#{@aliases[aliased_name]}"
+          else
+            aliased_name
+          end
+        end
+      end
+      
+      private
+      
+        def initialize_count_for(name)
+          @aliases[name] = 0
+          
+          unless @other_sql.blank?
+            # quoted_name should be downcased as some database adapters (Oracle) return quoted name in uppercase
+            quoted_name = connection.quote_table_name(name.downcase).downcase
+            
+            # Table names
+            @aliases[name] += @other_sql.scan(/join(?:\s+\w+)?\s+#{quoted_name}\son/).size
+            
+            # Table aliases
+            @aliases[name] += @other_sql.scan(/join(?:\s+\w+)?\s+\S+\s+#{quoted_name}\son/).size
+          end
+          
+          @aliases[name]
+        end
+        
+        def truncate(name)
+          name[0..connection.table_alias_length-3]
+        end
+        
+        def connection
+          ActiveRecord::Base.connection
+        end
+    end
+  end
+end