$OpenBSD: patch-src_bin_scripts_vacuumdb_c,v 1.4 2021/02/09 20:04:10 jeremy Exp $
Index: src/bin/scripts/vacuumdb.c
--- src/bin/scripts/vacuumdb.c.orig
+++ src/bin/scripts/vacuumdb.c
@@ -14,6 +14,8 @@
 #define FD_SETSIZE 1024			/* must set before winsock2.h is included */
 #endif
 
+#include <sys/select.h> /* FD_SETSIZE */
+
 #include "postgres_fe.h"
 
 #ifdef HAVE_SYS_SELECT_H
