Fix migration for MySQL

db/migrate/20120202190701_remove_public_share_visibilities.rb

@@ -23,15 +23,27 @@ class RemovePublicShareVisibilities < ActiveRecord::Migration
       end
 
       while index < shareable_size + 100 do
-        sql = <<-SQL
-          DELETE
-            FROM share_visibilities AS sv
-              USING #{table_name} as p
-              WHERE sv.shareable_id = p.id
-                AND sv.shareable_type = '#{type}'
-                AND p.public IS TRUE
-                AND p.id < #{index};
-        SQL
+        if postgres?
+          sql = <<-SQL
+            DELETE
+              FROM share_visibilities AS sv
+                USING #{table_name} as p
+                WHERE sv.shareable_id = p.id
+                  AND sv.shareable_type = '#{type}'
+                  AND p.public IS TRUE
+                  AND p.id < #{index};
+          SQL
+        else
+          sql = <<-SQL
+            DELETE sv
+              FROM share_visibilities AS sv
+              INNER JOIN #{table_name}
+              ON sv.shareable_id = #{table_name}.id
+              WHERE sv.shareable_type = "#{type}"
+                AND #{table_name}.public IS TRUE
+                AND #{table_name}.id < #{index};
+	        SQL
+        end
 
         puts "deleted public share vis up to #{index} of #{type}"
         ActiveRecord::Base.connection.execute(sql)