+#ifndef USE_MYSQL
+#ifndef USE_PGSQL
+#error One of USE_MYSQL or USE_PGSQL must be defined
+#endif
+#endif
+
+#ifdef USE_PGSQL
+#ifdef USE_MYSQL
+#error ONLY one of USE_MYSQL and USE_PGSQL should be defined
+#endif
+
+#include <postgres.h>
+#include <fmgr.h>
+
+int xid_to_int4(TransactionId xid)
+{
+ return xid;
+}
+
+/*
+ * To bind this into PGSQL, try something like:
+ *
+ * CREATE FUNCTION xid_to_int4(xid) RETURNS int4
+ * AS '/path/to/rails-port/db/functions/libpgosm', 'xid_to_int4'
+ * LANGUAGE C IMMUTABLE STRICT;
+ *
+ * (without all the *s)
+ */
+
+#endif