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

@@ -93,75 +93,79 @@ 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)
 	{
-		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 length
+		 * other than XLOG_FNAME_LEN.  (In principle, one could use a
+		 * 1000-character additional_ext and get trouble.)
+		 */
+		strlcpy(walfile, xlde->d_name, MAXPGPATH);
+		TrimExtension(walfile, additional_ext);
+
+		/*
+		 * Ignore anything does that not look like a WAL segment or a .partial
+		 * WAL segment.
+		 */
+		if (!IsXLogFileName(walfile) && !IsPartialXLogFileName(walfile))
+			continue;
+
+		/*
+		 * We ignore the timeline part of the XLOG segment identifiers in
+		 * deciding whether a segment is still needed.  This ensures that 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 (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);
+
+		if (dryrun)
 		{
 			/*
-			 * Truncation is essentially harmless, because we skip names of
-			 * length other than XLOG_FNAME_LEN.  (In principle, one could use
-			 * a 1000-character additional_ext and get trouble.)
+			 * Prints the name of the file to be removed and skips the actual
+			 * removal.  The regular printout is so that the user can pipe the
+			 * output into some other program.
 			 */
-			strlcpy(walfile, xlde->d_name, MAXPGPATH);
-			TrimExtension(walfile, additional_ext);
-
-			/*
-			 * We ignore the timeline part of the XLOG segment identifiers in
-			 * deciding whether a segment is still needed.  This ensures that
-			 * 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)) &&
-				strcmp(walfile + 8, exclusiveCleanupFileName + 8) < 0)
-			{
-				char		WALFilePath[MAXPGPATH * 2]; /* the file path
-														 * including archive */
-
-				/*
-				 * 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);
-
-				if (dryrun)
-				{
-					/*
-					 * Prints the name of the file to be removed and skips the
-					 * actual removal.  The regular printout is so that the
-					 * user can pipe the output into some other program.
-					 */
-					printf("%s\n", WALFilePath);
-					pg_log_debug("file \"%s\" would be removed", WALFilePath);
-					continue;
-				}
-
-				pg_log_debug("removing file \"%s\"", WALFilePath);
-
-				rc = unlink(WALFilePath);
-				if (rc != 0)
-					pg_fatal("could not remove file \"%s\": %m",
-							 WALFilePath);
-			}
+			printf("%s\n", WALFilePath);
+			pg_log_debug("file \"%s\" would be removed", WALFilePath);
+			continue;
 		}
 
-		if (errno)
-			pg_fatal("could not read archive location \"%s\": %m",
-					 archiveLocation);
-		if (closedir(xldir))
-			pg_fatal("could not close archive location \"%s\": %m",
-					 archiveLocation);
+		pg_log_debug("removing file \"%s\"", WALFilePath);
+
+		rc = unlink(WALFilePath);
+		if (rc != 0)
+			pg_fatal("could not remove file \"%s\": %m",
+					 WALFilePath);
 	}
-	else
-		pg_fatal("could not open archive location \"%s\": %m",
+
+	if (errno)
+		pg_fatal("could not read archive location \"%s\": %m",
+				 archiveLocation);
+	if (closedir(xldir))
+		pg_fatal("could not close archive location \"%s\": %m",
 				 archiveLocation);
 }