always return Postgres table names with schema to avoid awfulness

- without the schema, the migrations table gets truncated since the default AR method returns ‘public.schema_migrations’
- also a possibility is truncation of tables other than desired once since without the schema, Postgres has no way of knowing which table to truncate if two schemas have the same table

lib/database_cleaner/active_record/truncation.rb

@@ -24,6 +24,7 @@ module DatabaseCleaner
       def database_cleaner_view_cache
         @views ||= select_values("select table_name from information_schema.views where table_schema = '#{current_database}'") rescue []
       end
+      
       def database_cleaner_table_cache
         # the adapters don't do caching (#130) but we make the assumption that the list stays the same in tests
         @database_cleaner_tables ||= tables
@@ -155,6 +156,15 @@ module DatabaseCleaner
         truncate_tables(tables.select(&filter))
       end
 
+      def database_cleaner_table_cache
+        # AR returns a list of tables without schema but then returns a
+        # migrations table with the schema. There are other problems, too,
+        # with using the base list. If a table exists in multiple schemas
+        # within the search path, truncation without the schema name could
+        # result in confusing, if not unexpected results.
+        @database_cleaner_tables ||= tables_with_schema
+      end
+
       private
 
       # Returns a boolean indicating if the given table has an auto-inc number higher than 0.
@@ -169,6 +179,15 @@ module DatabaseCleaner
       def has_rows?(table)
         select_value("SELECT true FROM #{table} LIMIT 1;")
       end
+
+      def tables_with_schema
+        rows = select_rows <<-_SQL
+          SELECT schemaname || '.' || tablename
+          FROM pg_tables
+          WHERE tablename !~ '_prt_' AND schemaname = ANY (current_schemas(false))
+        _SQL
+        rows.collect { |result| result.first }
+      end
     end
   end
 end

spec/database_cleaner/active_record/truncation/postgresql_spec.rb

@@ -35,6 +35,12 @@ module ActiveRecord
         end
       end
 
+      describe '#database_cleaner_table_cache' do
+        it 'should default to the list of tables with their schema' do
+          connection.database_cleaner_table_cache.first.should match(/^public\./)
+        end
+      end
+
       it_behaves_like "an adapter with pre-count truncation" do
         let(:connection) { active_record_pg_connection }
       end