pg_archivecleanup: Refactor loop doing old segment removals

This commit refactors a bit the main loop of pg_archivecleanup that
handles the removal of old segments, reducing by one its level of
indentation.  This will help an incoming patch that adds a new option
related to the segment filtering logic.

Author: Atsushi Torikoshi
Reviewed-by: Kyotaro Horiguchi, Fujii Masao, Michael Paquier
Discussion: https://postgr.es/m/d660ef741ce3d82f3b4283f1cafd576c@oss.nttdata.com

src/bin/pg_archivecleanup/pg_archivecleanup.c

@@ -93,41 +93,50 @@ CleanupPriorWALFiles(void)
 	struct dirent *xlde;
 	char		walfile[MAXPGPATH];
 
-	if ((xldir = opendir(archiveLocation)) != NULL)
+	xldir = opendir(archiveLocation);
-	{
+	if (xldir == NULL)
+		pg_fatal("could not open archive location \"%s\": %m",
+				 archiveLocation);
+
 	while (errno = 0, (xlde = readdir(xldir)) != NULL)
 	{
+		char		WALFilePath[MAXPGPATH * 2]; /* the file path including
+												 * archive */
+
 		/*
-			 * Truncation is essentially harmless, because we skip names of
+		 * Truncation is essentially harmless, because we skip names of length
-			 * length other than XLOG_FNAME_LEN.  (In principle, one could use
+		 * other than XLOG_FNAME_LEN.  (In principle, one could use a
-			 * a 1000-character additional_ext and get trouble.)
+		 * 1000-character additional_ext and get trouble.)
 		 */
 		strlcpy(walfile, xlde->d_name, MAXPGPATH);
 		TrimExtension(walfile, additional_ext);
 
 		/*
-			 * We ignore the timeline part of the XLOG segment identifiers in
+		 * Ignore anything does that not look like a WAL segment or a .partial
-			 * deciding whether a segment is still needed.  This ensures that
+		 * WAL segment.
-			 * we won't prematurely remove a segment from a parent timeline.
-			 * We could probably be a little more proactive about removing
-			 * segments of non-parent timelines, but that would be a whole lot
-			 * more complicated.
-			 *
-			 * We use the alphanumeric sorting property of the filenames to
-			 * decide which ones are earlier than the exclusiveCleanupFileName
-			 * file. Note that this means files are not removed in the order
-			 * they were originally written, in case this worries you.
 		 */
-			if ((IsXLogFileName(walfile) || IsPartialXLogFileName(walfile)) &&
+		if (!IsXLogFileName(walfile) && !IsPartialXLogFileName(walfile))
-				strcmp(walfile + 8, exclusiveCleanupFileName + 8) < 0)
+			continue;
-			{
-				char		WALFilePath[MAXPGPATH * 2]; /* the file path
-														 * including archive */
 
 		/*
-				 * Use the original file name again now, including any
+		 * We ignore the timeline part of the XLOG segment identifiers in
-				 * extension that might have been chopped off before testing
+		 * deciding whether a segment is still needed.  This ensures that we
-				 * the sequence.
+		 * won't prematurely remove a segment from a parent timeline. We could
+		 * probably be a little more proactive about removing segments of
+		 * non-parent timelines, but that would be a whole lot more
+		 * complicated.
+		 *
+		 * We use the alphanumeric sorting property of the filenames to decide
+		 * which ones are earlier than the exclusiveCleanupFileName file. Note
+		 * that this means files are not removed in the order they were
+		 * originally written, in case this worries you.
+		 */
+		if (strcmp(walfile + 8, exclusiveCleanupFileName + 8) >= 0)
+			continue;
+
+		/*
+		 * Use the original file name again now, including any extension that
+		 * might have been chopped off before testing the sequence.
 		 */
 		snprintf(WALFilePath, sizeof(WALFilePath), "%s/%s",
 				 archiveLocation, xlde->d_name);
@@ -135,9 +144,9 @@ CleanupPriorWALFiles(void)
 		if (dryrun)
 		{
 			/*
-					 * Prints the name of the file to be removed and skips the
+			 * Prints the name of the file to be removed and skips the actual
-					 * actual removal.  The regular printout is so that the
+			 * removal.  The regular printout is so that the user can pipe the
-					 * user can pipe the output into some other program.
+			 * output into some other program.
 			 */
 			printf("%s\n", WALFilePath);
 			pg_log_debug("file \"%s\" would be removed", WALFilePath);
@@ -151,7 +160,6 @@ CleanupPriorWALFiles(void)
 			pg_fatal("could not remove file \"%s\": %m",
 					 WALFilePath);
 	}
-		}
 
 	if (errno)
 		pg_fatal("could not read archive location \"%s\": %m",
@@ -160,10 +168,6 @@ CleanupPriorWALFiles(void)
 		pg_fatal("could not close archive location \"%s\": %m",
 				 archiveLocation);
 }
-	else
-		pg_fatal("could not open archive location \"%s\": %m",
-				 archiveLocation);
-}
 
 /*
  * SetWALFileNameForCleanup()