pg_waldump: Add a --quiet option.

The primary motivation for this change is that it will be used by the
upcoming patch to add backup manifests, but it also seems to have some
potential more general use.

Andres Freund and Robert Haas

Discussion: http://postgr.es/m/20200330020814.nspra4mvby42yoa4@alap3.anarazel.de

doc/src/sgml/ref/pg_waldump.sgml

@@ -125,6 +125,18 @@ PostgreSQL documentation
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><option>-q</option></term>
+      <term><option>--quiet</option></term>
+      <listitem>
+       <para>
+        Do not print any output, except for errors. This option can be useful
+        when you want to know whether a range of WAL records can be
+        successfully parsed but don't care about the record contents.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><option>-r <replaceable>rmgr</replaceable></option></term>
       <term><option>--rmgr=<replaceable>rmgr</replaceable></option></term>

src/bin/pg_waldump/pg_waldump.c

@@ -40,6 +40,7 @@ typedef struct XLogDumpPrivate
 typedef struct XLogDumpConfig
 {
 	/* display options */
+	bool		quiet;
 	bool		bkp_details;
 	int			stop_after_records;
 	int			already_displayed_records;
@@ -720,6 +721,7 @@ usage(void)
 	printf(_("  -p, --path=PATH        directory in which to find log segment files or a\n"
 			 "                         directory with a ./pg_wal that contains such files\n"
 			 "                         (default: current directory, ./pg_wal, $PGDATA/pg_wal)\n"));
+	printf(_("  -q, --quiet            do not print any output, except for errors\n"));
 	printf(_("  -r, --rmgr=RMGR        only show records generated by resource manager RMGR;\n"
 			 "                         use --rmgr=list to list valid resource manager names\n"));
 	printf(_("  -s, --start=RECPTR     start reading at WAL location RECPTR\n"));
@@ -755,6 +757,7 @@ main(int argc, char **argv)
 		{"help", no_argument, NULL, '?'},
 		{"limit", required_argument, NULL, 'n'},
 		{"path", required_argument, NULL, 'p'},
+		{"quiet", no_argument, NULL, 'q'},
 		{"rmgr", required_argument, NULL, 'r'},
 		{"start", required_argument, NULL, 's'},
 		{"timeline", required_argument, NULL, 't'},
@@ -794,6 +797,7 @@ main(int argc, char **argv)
 	private.endptr = InvalidXLogRecPtr;
 	private.endptr_reached = false;
 
+	config.quiet = false;
 	config.bkp_details = false;
 	config.stop_after_records = -1;
 	config.already_displayed_records = 0;
@@ -810,7 +814,7 @@ main(int argc, char **argv)
 		goto bad_argument;
 	}
 
-	while ((option = getopt_long(argc, argv, "be:fn:p:r:s:t:x:z",
+	while ((option = getopt_long(argc, argv, "be:fn:p:qr:s:t:x:z",
 								 long_options, &optindex)) != -1)
 	{
 		switch (option)
@@ -840,6 +844,9 @@ main(int argc, char **argv)
 			case 'p':
 				waldir = pg_strdup(optarg);
 				break;
+			case 'q':
+				config.quiet = true;
+				break;
 			case 'r':
 				{
 					int			i;
@@ -1075,11 +1082,14 @@ main(int argc, char **argv)
 			config.filter_by_xid != record->xl_xid)
 			continue;
 
-		/* process the record */
-		if (config.stats == true)
-			XLogDumpCountRecord(&config, &stats, xlogreader_state);
-		else
-			XLogDumpDisplayRecord(&config, xlogreader_state);
+		/* perform any per-record work */
+		if (!config.quiet)
+		{
+			if (config.stats == true)
+				XLogDumpCountRecord(&config, &stats, xlogreader_state);
+			else
+				XLogDumpDisplayRecord(&config, xlogreader_state);
+		}
 
 		/* check whether we printed enough */
 		config.already_displayed_records++;