1 files changed, 78 insertions, 0 deletions
diff --git a/src/include/catalog/unused_oids b/src/include/catalog/unused_oids
new file mode 100755
index 0000000..5b7ce5f
--- /dev/null
+++ b/src/include/catalog/unused_oids
@@ -0,0 +1,78 @@
+#!/usr/bin/perl
+#----------------------------------------------------------------------
+#
+# unused_oids
+#    Finds blocks of manually-assignable OIDs that have not already been
+#    claimed by previous hackers.  The main use is for finding available
+#    OIDs for new internal functions.  The numbers printed are inclusive
+#    ranges of unused OIDs.
+#
+#    Before using a large empty block, make sure you aren't about
+#    to take over what was intended as expansion space for something
+#    else.
+#
+# Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+# Portions Copyright (c) 1994, Regents of the University of California
+#
+# src/include/catalog/unused_oids
+#
+#----------------------------------------------------------------------
+
+use strict;
+use warnings;
+
+# Must run in src/include/catalog
+use FindBin;
+chdir $FindBin::RealBin or die "could not cd to $FindBin::RealBin: $!\n";
+
+use lib "$FindBin::RealBin/../../backend/catalog/";
+use Catalog;
+
+my @input_files = glob("pg_*.h");
+
+my $oids = Catalog::FindAllOidsFromHeaders(@input_files);
+
+# Also push FirstGenbkiObjectId to serve as a terminator for the last gap.
+my $FirstGenbkiObjectId =
+  Catalog::FindDefinedSymbol('access/transam.h', '..', 'FirstGenbkiObjectId');
+push @{$oids}, $FirstGenbkiObjectId;
+
+my $prev_oid = 0;
+my @sortedoids = sort { $a <=> $b } @{$oids};
+foreach my $oid (@sortedoids)
+{
+	if ($oid > $prev_oid + 1)
+	{
+		if ($oid > $prev_oid + 2)
+		{
+			printf "%d - %d\n", $prev_oid + 1, $oid - 1;
+		}
+		else
+		{
+			printf "%d\n", $prev_oid + 1;
+		}
+	}
+	$prev_oid = $oid;
+}
+
+my $suggestion;
+do
+{
+	$suggestion = int(8000 + rand(2000));
+} while (grep(/^$suggestion$/, @{$oids}));
+
+my $navailable = 0;
+foreach my $oid (@sortedoids)
+{
+	if ($oid > $suggestion)
+	{
+		$navailable = $oid - $suggestion;
+		last;
+	}
+}
+
+printf "Patches should use a more-or-less consecutive range of OIDs.\n";
+printf
+  "Best practice is to start with a random choice in the range 8000-9999.\n";
+printf
+  "Suggested random unused OID: $suggestion ($navailable consecutive OID(s) available starting here)\n";