Use faster group columns if not running on postgresql

lib/acts_as_taggable_on/acts_as_taggable_on/collection.rb

@@ -91,7 +91,6 @@ def all_tag_counts(options = {})
 
         joins = joins.reverse if ActiveRecord::VERSION::MAJOR < 3
 
-
         ## Generate scope:
         scope = ActsAsTaggableOn::Tag.scoped(:select => "#{ActsAsTaggableOn::Tag.table_name}.*, COUNT(*) AS count").order(options[:order]).limit(options[:limit])   
 
@@ -104,17 +103,19 @@ def all_tag_counts(options = {})
         at_most   = sanitize_sql(['COUNT(*) <= ?', options.delete(:at_most)]) if options[:at_most]
         having    = [at_least, at_most].compact.join(' AND ')        
 
+        group_columns = ActsAsTaggableOn::Tag.using_postgresql? ? grouped_column_names_for(ActsAsTaggableOn::Tag) : "#{ActsAsTaggableOn::Tag.table_name}.#{ActsAsTaggableOn::Tag.primary_key}"
+
         if ActiveRecord::VERSION::MAJOR >= 3
           # Append the current scope to the scope, because we can't use scope(:find) in RoR 3.0 anymore:
           scoped_select = "#{table_name}.#{primary_key}"
           scope = scope.where("#{ActsAsTaggableOn::Tagging.table_name}.taggable_id IN(#{select(scoped_select).to_sql})")
 
           # We have having() in RoR 3.0 so use it:
           having = having.blank? ? "COUNT(*) > 0" : "COUNT(*) > 0 AND #{having}"
-          scope = scope.group(grouped_column_names_for(ActsAsTaggableOn::Tag)).having(having)
+          scope = scope.group(group_columns).having(having)
         else
           # Having is not available in 2.3.x:
-          group_by  = "#{grouped_column_names_for(ActsAsTaggableOn::Tag)} HAVING COUNT(*) > 0"
+          group_by  = "#{group_columns} HAVING COUNT(*) > 0"
           group_by << " AND #{having}" unless having.blank?
           scope = scope.group(group_by)
         end

lib/acts_as_taggable_on/acts_as_taggable_on/core.rb

@@ -110,7 +110,9 @@ def tagged_with(tags, options = {})
                    "  ON #{taggings_alias}.taggable_id = #{table_name}.#{primary_key}" +
                    " AND #{taggings_alias}.taggable_type = #{quote_value(base_class.name)}"
 
-          group = "#{grouped_column_names_for(self)} HAVING COUNT(#{taggings_alias}.taggable_id) = #{tags.size}"
+
+          group_columns = ActsAsTaggableOn::Tag.using_postgresql? ? grouped_column_names_for(self) : "#{table_name}.#{primary_key}"
+          group = "#{group_columns} HAVING COUNT(#{taggings_alias}.taggable_id) = #{tags.size}"
         end
 
 
@@ -176,8 +178,17 @@ def all_tags_on(context)
         tag_table_name = ActsAsTaggableOn::Tag.table_name
         tagging_table_name = ActsAsTaggableOn::Tagging.table_name
 
-        opts =  ["#{tagging_table_name}.context = ?", context.to_s]
-        base_tags.where(opts).order("max(#{tagging_table_name}.created_at)").group("#{tag_table_name}.id, #{tag_table_name}.name").all
+        opts  =  ["#{tagging_table_name}.context = ?", context.to_s]
+        scope = base_tags.where(opts)
+
+        if ActsAsTaggableOn::Tag.using_postgresql?
+          group_columns = grouped_column_names_for(ActsAsTaggableOn::Tag)
+          scope = scope.order("max(#{tagging_table_name}.created_at)").group(group_columns)
+        else
+          scope = scope.group("#{ActsAsTaggableOn::Tag.table_name}.#{ActsAsTaggableOn::Tag.primary_key}")
+        end
+
+        scope.all
       end
 
       ##

lib/acts_as_taggable_on/acts_as_taggable_on/related.rb

@@ -42,10 +42,12 @@ def matching_contexts_for(search_context, result_context, klass, options = {})
 
         exclude_self = "#{klass.table_name}.id != #{id} AND" if self.class == klass
 
+        group_columns = ActsAsTaggableOn::Tag.using_postgresql? ? grouped_column_names_for(klass) : "#{klass.table_name}.#{klass.primary_key}"
+
         klass.scoped({ :select     => "#{klass.table_name}.*, COUNT(#{ActsAsTaggableOn::Tag.table_name}.id) AS count",
                        :from       => "#{klass.table_name}, #{ActsAsTaggableOn::Tag.table_name}, #{ActsAsTaggableOn::Tagging.table_name}",
                        :conditions => ["#{exclude_self} #{klass.table_name}.id = #{ActsAsTaggableOn::Tagging.table_name}.taggable_id AND #{ActsAsTaggableOn::Tagging.table_name}.taggable_type = '#{klass.to_s}' AND #{ActsAsTaggableOn::Tagging.table_name}.tag_id = #{ActsAsTaggableOn::Tag.table_name}.id AND #{ActsAsTaggableOn::Tag.table_name}.name IN (?) AND #{ActsAsTaggableOn::Tagging.table_name}.context = ?", tags_to_find, result_context],
-                       :group      => grouped_column_names_for(klass),
+                       :group      => group_columns,
                        :order      => "count DESC" }.update(options))
       end
 
@@ -54,10 +56,12 @@ def related_tags_for(context, klass, options = {})
 
         exclude_self = "#{klass.table_name}.id != #{id} AND" if self.class == klass
 
+group_columns = ActsAsTaggableOn::Tag.using_postgresql? ? grouped_column_names_for(klass) : "#{klass.table_name}.#{klass.primary_key}"
+
         klass.scoped({ :select     => "#{klass.table_name}.*, COUNT(#{ActsAsTaggableOn::Tag.table_name}.id) AS count",
                        :from       => "#{klass.table_name}, #{ActsAsTaggableOn::Tag.table_name}, #{ActsAsTaggableOn::Tagging.table_name}",
                        :conditions => ["#{exclude_self} #{klass.table_name}.id = #{ActsAsTaggableOn::Tagging.table_name}.taggable_id AND #{ActsAsTaggableOn::Tagging.table_name}.taggable_type = '#{klass.to_s}' AND #{ActsAsTaggableOn::Tagging.table_name}.tag_id = #{ActsAsTaggableOn::Tag.table_name}.id AND #{ActsAsTaggableOn::Tag.table_name}.name IN (?)", tags_to_find],
-                       :group      => grouped_column_names_for(klass),
+                       :group      => group_columns,
                        :order      => "count DESC" }.update(options))
       end
     end

lib/acts_as_taggable_on/tag.rb

@@ -14,6 +14,10 @@ class Tag < ::ActiveRecord::Base
     validates_uniqueness_of :name
 
     ### SCOPES:
+
+    def self.using_postgresql?
+      connection.adapter_name == 'PostgreSQL'
+    end
 
     def self.named(name)
       where(["name #{like_operator} ?", name])
@@ -66,7 +70,7 @@ def count
     class << self
       private
         def like_operator
-          connection.adapter_name == 'PostgreSQL' ? 'ILIKE' : 'LIKE'
+          using_postgresql? ? 'ILIKE' : 'LIKE'
         end
     end