Add option -N/--no-sync to pg_upgrade

This is an option consistent with what the other tools of src/bin/
(pg_checksums, pg_dump, pg_rewind and pg_basebackup) provide which is
useful for leveraging the I/O effort when testing things.  This is not
to be used in a production environment.

All the regression tests of pg_upgrade are updated to use this new
option.  This happens to cut at most a couple of seconds in environments
constrained on I/O, by avoiding a flush of data folder for the new
cluster upgraded.

Author: Michael Paquier
Reviewed-by: Peter Eisentraut
Discussion: https://postgr.es/m/YbrhzuBmBxS/DkfX@paquier.xyz

doc/src/sgml/ref/pgupgrade.sgml

@@ -130,6 +130,22 @@ PostgreSQL documentation
       cluster</para></listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><option>-N</option></term>
+      <term><option>--no-sync</option></term>
+      <listitem>
+       <para>
+        By default, <command>pg_upgrade</command> will wait for all files
+        of the upgraded cluster to be written safely to disk.  This option
+        causes <command>pg_upgrade</command> to return without waiting, which
+        is faster, but means that a subsequent operating system crash can leave
+        the synchronized data directory corrupt.  Generally, this option is
+        useful for testing but should not be used on a production
+        installation.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><option>-o</option> <replaceable class="parameter">options</replaceable></term>
       <term><option>--old-options</option> <replaceable class="parameter">options</replaceable></term>

src/bin/pg_upgrade/option.c

@@ -43,6 +43,7 @@ parseCommandLine(int argc, char *argv[])
 		{"new-datadir", required_argument, NULL, 'D'},
 		{"old-bindir", required_argument, NULL, 'b'},
 		{"new-bindir", required_argument, NULL, 'B'},
+		{"no-sync", no_argument, NULL, 'N'},
 		{"old-options", required_argument, NULL, 'o'},
 		{"new-options", required_argument, NULL, 'O'},
 		{"old-port", required_argument, NULL, 'p'},
@@ -66,6 +67,7 @@ parseCommandLine(int argc, char *argv[])
 	char	  **filename;
 	time_t		run_time = time(NULL);
 
+	user_opts.do_sync = true;
 	user_opts.transfer_mode = TRANSFER_MODE_COPY;
 
 	os_info.progname = get_progname(argv[0]);
@@ -101,7 +103,7 @@ parseCommandLine(int argc, char *argv[])
 	if (os_user_effective_id == 0)
 		pg_fatal("%s: cannot be run as root\n", os_info.progname);
 
-	while ((option = getopt_long(argc, argv, "d:D:b:B:cj:ko:O:p:P:rs:U:v",
+	while ((option = getopt_long(argc, argv, "d:D:b:B:cj:kNo:O:p:P:rs:U:v",
 								 long_options, &optindex)) != -1)
 	{
 		switch (option)
@@ -134,6 +136,10 @@ parseCommandLine(int argc, char *argv[])
 				user_opts.transfer_mode = TRANSFER_MODE_LINK;
 				break;
 
+			case 'N':
+				user_opts.do_sync = false;
+				break;
+
 			case 'o':
 				/* append option? */
 				if (!old_cluster.pgopts)
@@ -286,6 +292,7 @@ usage(void)
 	printf(_("  -D, --new-datadir=DATADIR     new cluster data directory\n"));
 	printf(_("  -j, --jobs=NUM                number of simultaneous processes or threads to use\n"));
 	printf(_("  -k, --link                    link instead of copying files to new cluster\n"));
+	printf(_("  -N, --no-sync                 do not wait for changes to be written safely to disk\n"));
 	printf(_("  -o, --old-options=OPTIONS     old cluster options to pass to the server\n"));
 	printf(_("  -O, --new-options=OPTIONS     new cluster options to pass to the server\n"));
 	printf(_("  -p, --old-port=PORT           old cluster port number (default %d)\n"), old_cluster.port);

src/bin/pg_upgrade/pg_upgrade.c

@@ -169,11 +169,14 @@ main(int argc, char **argv)
 			  new_cluster.pgdata);
 	check_ok();
 
+	if (user_opts.do_sync)
+	{
 		prep_status("Sync data directory to disk");
 		exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 				  "\"%s/initdb\" --sync-only \"%s\"", new_cluster.bindir,
 				  new_cluster.pgdata);
 		check_ok();
+	}
 
 	create_script_for_old_cluster_deletion(&deletion_script_file_name);
 

src/bin/pg_upgrade/pg_upgrade.h

@@ -279,6 +279,7 @@ typedef struct
 {
 	bool		check;			/* true -> ask user for permission to make
 								 * changes */
+	bool		do_sync;		/* flush changes to disk */
 	transferMode transfer_mode; /* copy files or link them? */
 	int			jobs;			/* number of processes/threads to use */
 	char	   *socketdir;		/* directory to use for Unix sockets */

src/bin/pg_upgrade/test.sh

@@ -233,7 +233,7 @@ PGDATA="$BASE_PGDATA"
 
 standard_initdb 'initdb'
 
-pg_upgrade $PG_UPGRADE_OPTS -d "${PGDATA}.old" -D "$PGDATA" -b "$oldbindir" -p "$PGPORT" -P "$PGPORT"
+pg_upgrade $PG_UPGRADE_OPTS --no-sync -d "${PGDATA}.old" -D "$PGDATA" -b "$oldbindir" -p "$PGPORT" -P "$PGPORT"
 
 # make sure all directories and files have group permissions, on Unix hosts
 # Windows hosts don't support Unix-y permissions.

src/tools/msvc/vcregress.pl

@@ -648,7 +648,9 @@ sub upgradecheck
 	print "\nSetting up new cluster\n\n";
 	standard_initdb() or exit 1;
 	print "\nRunning pg_upgrade\n\n";
-	@args = ('pg_upgrade', '-d', "$data.old", '-D', $data, '-b', $bindir);
+	@args = (
+		'pg_upgrade', '-d', "$data.old", '-D', $data, '-b', $bindir,
+		'--no-sync');
 	system(@args) == 0 or exit 1;
 	print "\nStarting new cluster\n\n";
 	@args = ('pg_ctl', '-l', "$logdir/postmaster2.log", 'start');