Add new -x XID option to /contrib/pg_resetxlog for future pg_upgrade use.

contrib/pg_resetxlog/README.pg_resetxlog

@@ -21,6 +21,9 @@ module pg_controldata and run it to be sure the DB state is SHUTDOWN).
 Then run pg_resetxlog, and finally install and start the new version of
 the database software.
 
+A tertiary purpose it its use by pg_upgrade to set the next transaction
+id in pg_control.
+
 To run the program, make sure your postmaster is not running, then
 (as the Postgres admin user) do
 

contrib/pg_resetxlog/pg_resetxlog.c

@@ -23,7 +23,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Header: /cvsroot/pgsql/contrib/pg_resetxlog/Attic/pg_resetxlog.c,v 1.10 2001/11/05 17:46:23 momjian Exp $
+ * $Header: /cvsroot/pgsql/contrib/pg_resetxlog/Attic/pg_resetxlog.c,v 1.11 2002/01/10 17:51:52 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -709,11 +709,13 @@ PrintControlValues(void)
  * Write out the new pg_control file.
  */
 static void
-RewriteControlFile(void)
+RewriteControlFile(TransactionId set_xid)
 {
 	int			fd;
 	char		buffer[BLCKSZ]; /* need not be aligned */
 
+	if (set_xid == 0)
+	{
 		/*
 		 * Adjust fields as needed to force an empty XLOG starting at the next
 		 * available segment.
@@ -736,6 +738,9 @@ RewriteControlFile(void)
 		ControlFile.checkPoint = ControlFile.checkPointCopy.redo;
 		ControlFile.prevCheckPoint.xlogid = 0;
 		ControlFile.prevCheckPoint.xrecoff = 0;
+	}
+	else
+		ControlFile.checkPointCopy.nextXid = set_xid;
 	
 	/* Contents are protected with a CRC */
 	INIT_CRC64(ControlFile.crc);
@@ -926,9 +931,10 @@ WriteEmptyXLOG(void)
 static void
 usage(void)
 {
-	fprintf(stderr, "Usage: pg_resetxlog [-f] [-n] PGDataDirectory\n\n"
+	fprintf(stderr, "Usage: pg_resetxlog [-f] [-n] [-x xid] PGDataDirectory\n"
 			" -f\tforce update to be done\n"
-			"  -n\tno update, just show extracted pg_control values (for testing)\n");
+			" -n\tno update, just show extracted pg_control values (for testing)\n"
+			" -x XID\tset XID in pg_control\n");
 	exit(1);
 }
 
@@ -939,6 +945,7 @@ main(int argc, char **argv)
 	int			argn;
 	bool		force = false;
 	bool		noupdate = false;
+	TransactionId set_xid = 0;
 	int			fd;
 	char		path[MAXPGPATH];
 
@@ -950,6 +957,18 @@ main(int argc, char **argv)
 			force = true;
 		else if (strcmp(argv[argn], "-n") == 0)
 			noupdate = true;
+		else if (strcmp(argv[argn], "-x") == 0)
+		{
+			argn++;
+			if (argn == argc)
+				usage();
+			set_xid = strtoul(argv[argn], NULL, 0);
+			if (set_xid == 0)
+			{
+				fprintf(stderr, "XID can not be 0.");
+				exit(1);
+			}
+		}
 		else
 			usage();
 	}
@@ -992,6 +1011,20 @@ main(int argc, char **argv)
 	if (!ReadControlFile())
 		GuessControlValues();
 
+	/*
+	 * Set XID in pg_control and exit
+	 */
+	if (set_xid)
+	{
+		if (guessed)
+		{
+			printf("\npg_control appears corrupt.  Can not update XID.\n");
+			exit(1);
+		}
+		RewriteControlFile(set_xid);
+		exit(0);
+	}
+
 	/*
 	 * If we had to guess anything, and -f was not given, just print the
 	 * guessed values and exit.  Also print if -n is given.
@@ -1018,7 +1051,7 @@ main(int argc, char **argv)
 	/*
 	 * Else, do the dirty deed.
 	 */
-	RewriteControlFile();
+	RewriteControlFile(0);
 	KillExistingXLOG();
 	WriteEmptyXLOG();