Monkey patch rails to make system table query efficient

[rails.git] / config / initializers / postgresql_adapter.rb

diff --git a/config/initializers/postgresql_adapter.rb b/config/initializers/postgresql_adapter.rb
new file mode 100644 (file)
index 0000000..0420a74
--- /dev/null
+++ b/config/initializers/postgresql_adapter.rb
@@ -0,0 +1,34 @@
+module ActiveRecord
+  module ConnectionAdapters
+    class PostgreSQLAdapter
+      alias_method :old_pk_and_sequence_for, :pk_and_sequence_for
+
+      def pk_and_sequence_for(table)
+        result = query(<<-end_sql, 'PK and serial sequence')[0]
+          SELECT attr.attname, seq.relname
+          FROM pg_class      seq,
+               pg_attribute  attr,
+               pg_depend     dep,
+               pg_namespace  name,
+               pg_constraint cons
+          WHERE seq.oid           = dep.objid
+            AND seq.relkind       = 'S'
+            AND attr.attrelid     = dep.refobjid
+            AND attr.attnum       = dep.refobjsubid
+            AND attr.attrelid     = cons.conrelid
+            AND attr.attnum       = cons.conkey[1]
+            AND cons.contype      = 'p'
+            AND dep.classid       = '"pg_class"'::regclass
+            AND dep.refclassid    = '"pg_class"'::regclass
+            AND dep.refobjid      = '#{quote_table_name(table)}'::regclass
+        end_sql
+
+        if result.nil? or result.empty?
+          old_pk_and_sequence_for(table)
+        else
+          [result.first, result.last]
+        end
+      end
+    end
+  end
+end