From: Keith Parks <emkxp01@mtcc.demon.co.uk>

OK, The votes are in for the NOFILES limit.

With the exception of Next, for which I've not yet heard, all supported platforms
seem to have the sysconf() call.


port           supported	default	Source.
aix            yes		2000	darrenk@insightdist.com
alpha          yes		4096	mjl@wwx.vip.at
BSD44_derived  yes		64	scrappy@hub.org
bsdi           yes		???	maillist@candle.pha.pa.us
dgux           yes		???	geek@andrew.cmu.edu
hpux           yes		60	emkxp01@mtcc.demon.co.uk
i386_solaris   yes		64	emkxp01@mtcc.demon.co.uk
irix5          yes		200	martin@biochem.uc.ac.uk
linux          yes		256	emkxp01@mtcc.demon.co.uk
next           ????		???
sparc_solaris  yes		64	emkxp01@mtcc.demon.co.uk
sunos4         yes		64	emkxp01@mtcc.demon.co.uk
svr4           yes		64	chicks@chicks.net
ultrix4        yes		64	erik@sockdev.uni-c.dk

So here's a patch that I think will do the job.
(I assume Next will have sysconf() but if not just add MISSING_SYSCONF to
 the config.h file )

Thanks,
Keith.

src/backend/storage/file/fd.c

@@ -6,7 +6,7 @@
  * Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *    $Id: fd.c,v 1.12 1996/12/28 22:44:14 momjian Exp $
+ *    $Id: fd.c,v 1.13 1997/01/13 01:25:29 scrappy Exp $
  *
  * NOTES:
  *
@@ -52,21 +52,6 @@
 #include "utils/palloc.h"
 #include "storage/fd.h"
 
-#if defined(NEED_NOFILE_KLUDGE)
-/*
- * the SunOS 4 NOFILE is a lie, because the default limit is *not* the
- * maximum number of file descriptors you can have open.
- *
- * we have to either use this number (the default dtablesize) or
- * explicitly call setrlimit(RLIMIT_NOFILE, NOFILE).
- *
- * this braindamage apparently also affects solaris 2.X as well
- */
-#include <sys/user.h>
-#undef NOFILE
-#define NOFILE NOFILE_IN_U
-#endif /* NEED_NOFILE_KLUDGE */
-
 /*
  * Problem: Postgres does a system(ld...) to do dynamic loading.  This
  * will open several extra files in addition to those used by
@@ -81,23 +66,21 @@
  * equivalent, the OS must still open several files to perform the
  * dynamic loading.  Keep this here.)
  */
+#ifndef RESERVE_FOR_LD
 #define RESERVE_FOR_LD  10
+#endif 
 
 /*
- * If we are using weird storage managers, we may need to keep real
- * file descriptors open so that the jukebox server doesn't think we
- * have gone away (and no longer care about a platter or file that
- * we've been using).  This might be an actual file descriptor for a
- * local jukebox interface that uses paths, or a socket connection for
- * a network jukebox server.  Since we can't be opening and closing
- * these descriptors at whim, we must make allowances for them.
+ * We need to ensure that we have at least some file descriptors
+ * available to postgreSQL after we've reserved the ones for LD,
+ * so we set that value here.
+ *
+ * I think 10 is an apropriate value so that's what it'll be
+ * for now.
  */
-#ifdef HP_JUKEBOX
-#define RESERVE_FOR_JB  25
-#define MAXFILES        ((NOFILE - RESERVE_FOR_LD) - RESERVE_FOR_JB)
-#else /* HP_JUKEBOX */
-#define MAXFILES        (NOFILE - RESERVE_FOR_LD)
-#endif /* HP_JUKEBOX */
+#ifndef FD_MINFREE
+#define FD_MINFREE 10
+#endif
 
 /* Debugging.... */
 
@@ -197,6 +180,7 @@ static void FreeVfd(File file);
 static int FileAccess(File file);
 static File fileNameOpenFile(FileName fileName, int fileFlags, int fileMode);
 static char *filepath(char *filename);
+static long pg_nofile(void);
 
 int
 pg_fsync(int fd)
@@ -206,6 +190,30 @@ pg_fsync(int fd)
 }
 #define fsync pg_fsync
 
+long
+pg_nofile(void)
+{
+        static long no_files = 0;
+
+        if (no_files == 0) {
+#if defined(MISSING_SYSCONF)
+		no_files = (long)NOFILE;
+#else
+                no_files = sysconf(_SC_OPEN_MAX);
+		if (no_files == -1) {
+        		elog(DEBUG,"pg_nofile: Unable to get _SC_OPEN_MAX using sysconf() using (%d)", NOFILE);
+			no_files = (long)NOFILE;
+		}
+#endif /* MISSING_SYSCONF */
+        }
+
+	if ((no_files - RESERVE_FOR_LD) < FD_MINFREE)
+		elog(FATAL,"pg_nofile: insufficient File Descriptors in postmaster to start backend (%ld).\n"
+			   "                   O/S allows %ld, Postmaster reserves %d, We need %d (MIN) after that.",
+			 no_files - RESERVE_FOR_LD, no_files, RESERVE_FOR_LD, FD_MINFREE);
+        return no_files - RESERVE_FOR_LD;
+}
+
 #if defined(FDDEBUG)
 static void
 _dump_lru()
@@ -374,7 +382,7 @@ AssertLruRoom()
     DO_DB(printf("DEBUG:        AssertLruRoom (FreeFd = %d)\n",
                  FreeFd));
     
-    if (FreeFd <= 0 || nfile >= MAXFILES) {
+    if (FreeFd <= 0 || nfile >= pg_nofile()) {
         /* We supposedly are using more vfds than we want to be.  First
            assert that there is at least one used vfd in the ring. 
            */
@@ -550,7 +558,7 @@ fileNameOpenFile(FileName fileName,
     file = AllocateVfd();
     vfdP = &VfdCache[file];
     
-    if (nfile >= MAXFILES || (FreeFd == 0 && osRanOut)) {
+    if (nfile >= pg_nofile() || (FreeFd == 0 && osRanOut)) {
         AssertLruRoom();
     }
     
@@ -858,7 +866,7 @@ AllocateFile()
     }
     close(fd);
     ++allocatedFiles;
-    fdleft = MAXFILES - allocatedFiles;
+    fdleft = pg_nofile() - allocatedFiles;
     if (fdleft < 6) {
         elog(DEBUG,"warning: few usable file descriptors left (%d)", fdleft);
     }

src/include/config.h

@@ -102,7 +102,6 @@
 #  define HAVE_TZSET
 #  define NEED_UNION_SEMUN 
 #  define SYSV_DIRENT
-#  define NEED_NOFILE_KLUDGE
 #  define SB_PAD 56
 #  define HAS_TEST_AND_SET
    typedef unsigned char slock_t;
@@ -172,7 +171,6 @@ typedef unsigned char slock_t;
 
 #if defined(sunos4)
 #  define USE_POSIX_TIME
-#  define NEED_NOFILE_KLUDGE
 #  define SB_PAD 56
 #  undef HAVE_MEMMOVE
 #endif