[Issue #66] Correctly handle zero-sized nonedata files during incremental restore

Author: gsmolk

src/data.c

@@ -711,7 +711,7 @@ backup_non_data_file(pgFile *file, pgFile *prev_file,
 	}
 
 	/*
-	 * If non-data file exists in previous backup
+	 * If nonedata file exists in previous backup
 	 * and its mtime is less than parent backup start time ... */
 	if (prev_file && file->exists_in_prev &&
 		file->mtime <= parent_backup_time)
@@ -1136,7 +1136,7 @@ restore_non_data_file_internal(FILE *in, FILE *out, pgFile *file,
 
 		/* check for interrupt */
 		if (interrupted || thread_interrupted)
-			elog(ERROR, "Interrupted during non-data file restore");
+			elog(ERROR, "Interrupted during nonedata file restore");
 
 		read_len = fread(buf, 1, STDIO_BUFSIZE, in);
 
@@ -1165,7 +1165,6 @@ restore_non_data_file(parray *parent_chain, pgBackup *dest_backup,
 					  pgFile *dest_file, FILE *out, const char *to_fullpath,
 					  bool already_exists)
 {
-//	int			i;
 	char		from_root[MAXPGPATH];
 	char		from_fullpath[MAXPGPATH];
 	FILE		*in = NULL;
@@ -1203,14 +1202,19 @@ restore_non_data_file(parray *parent_chain, pgBackup *dest_backup,
 			 */
 			if (!tmp_file)
 			{
-				elog(ERROR, "Failed to locate non-data file \"%s\" in backup %s",
+				elog(ERROR, "Failed to locate nonedata file \"%s\" in backup %s",
 					dest_file->rel_path, base36enc(tmp_backup->start_time));
 				continue;
 			}
 
 			/* Full copy is found and it is null sized, nothing to do here */
 			if (tmp_file->write_size == 0)
+			{
+				/* In case of incremental restore truncate file just to be safe */
+				if (already_exists && fio_ftruncate(out, 0))
+					elog(ERROR, "Cannot truncate file \"%s\": %s", strerror(errno));
 				return 0;
+			}
 
 			/* Full copy is found */
 			if (tmp_file->write_size > 0)
@@ -1222,14 +1226,14 @@ restore_non_data_file(parray *parent_chain, pgBackup *dest_backup,
 
 	/* sanity */
 	if (!tmp_backup)
-		elog(ERROR, "Failed to found a backup containing full copy of non-data file \"%s\"",
+		elog(ERROR, "Failed to locate a backup containing full copy of nonedata file \"%s\"",
 			to_fullpath);
 
 	if (!tmp_file)
-		elog(ERROR, "Failed to locate a full copy of non-data file \"%s\"", to_fullpath);
+		elog(ERROR, "Failed to locate a full copy of nonedata file \"%s\"", to_fullpath);
 
 	if (tmp_file->write_size <= 0)
-		elog(ERROR, "Full copy of non-data file has invalid size. "
+		elog(ERROR, "Full copy of nonedata file has invalid size. "
 				"Metadata corruption in backup %s in file: \"%s\"",
 				base36enc(tmp_backup->start_time), to_fullpath);
 
@@ -1245,6 +1249,10 @@ restore_non_data_file(parray *parent_chain, pgBackup *dest_backup,
 				to_fullpath);
 			return 0;
 		}
+
+		/* Checksum mismatch, truncate file and overwrite it */
+		if (fio_ftruncate(out, 0))
+			elog(ERROR, "Cannot truncate file \"%s\": %s", strerror(errno));
 	}
 
 	if (tmp_file->external_dir_num == 0)
@@ -1264,7 +1272,7 @@ restore_non_data_file(parray *parent_chain, pgBackup *dest_backup,
 		elog(ERROR, "Cannot open backup file \"%s\": %s", from_fullpath,
 			 strerror(errno));
 
-	/* disable stdio buffering for non-data files */
+	/* disable stdio buffering for nonedata files */
 	setvbuf(in, NULL, _IONBF, BUFSIZ);
 
 	/* do actual work */
@@ -1793,7 +1801,7 @@ get_checksum_map(const char *fullpath, uint32 checksum_version,
 	char        in_buf[STDIO_BUFSIZE];
 
 	/* open file */
-	in = fopen(fullpath, PG_BINARY_R);
+	in = fopen(fullpath, "r+");
 	if (!in)
 		elog(ERROR, "Cannot open source file \"%s\": %s", fullpath, strerror(errno));
 
@@ -1864,7 +1872,7 @@ get_lsn_map(const char *fullpath, uint32 checksum_version,
 	Assert(shift_lsn > 0);
 
 	/* open file */
-	in = fopen(fullpath, PG_BINARY_R);
+	in = fopen(fullpath, "r+");
 	if (!in)
 		elog(ERROR, "Cannot open source file \"%s\": %s", fullpath, strerror(errno));
 

src/merge.c

@@ -1342,7 +1342,7 @@ merge_non_data_file(parray *parent_chain, pgBackup *full_backup,
 		 */
 		if (!from_file)
 		{
-			elog(ERROR, "Failed to locate non-data file \"%s\" in backup %s",
+			elog(ERROR, "Failed to locate nonedata file \"%s\" in backup %s",
 				dest_file->rel_path, base36enc(from_backup->start_time));
 			continue;
 		}
@@ -1353,11 +1353,11 @@ merge_non_data_file(parray *parent_chain, pgBackup *full_backup,
 
 	/* sanity */
 	if (!from_backup)
-		elog(ERROR, "Failed to found a backup containing full copy of non-data file \"%s\"",
+		elog(ERROR, "Failed to found a backup containing full copy of nonedata file \"%s\"",
 			dest_file->rel_path);
 
 	if (!from_file)
-		elog(ERROR, "Failed to locate a full copy of non-data file \"%s\"", dest_file->rel_path);
+		elog(ERROR, "Failed to locate a full copy of nonedata file \"%s\"", dest_file->rel_path);
 
 	/* set path to source file */
 	if (from_file->external_dir_num)

src/restore.c

@@ -470,8 +470,8 @@ do_restore_or_validate(time_t target_backup_id, pgRecoveryTarget *rt,
 					base36enc(dest_backup->start_time),
 					(uint32) (redo.lsn >> 32), (uint32) redo.lsn, redo.tli);
 		else
-			elog(INFO, "Destination directory redo point %X/%X on tli %i is within reach of "
-					"backup %s with Stop LSN %X/%X on tli %i, incremental restore in 'lsn' mode is possible",
+			elog(INFO, "Destination directory redo point %X/%X on tli %i is "
+					"within reach of backup %s with Stop LSN %X/%X on tli %i",
 				(uint32) (redo.lsn >> 32), (uint32) redo.lsn, redo.tli,
 				base36enc(tmp_backup->start_time),
 				(uint32) (tmp_backup->stop_lsn >> 32), (uint32) tmp_backup->stop_lsn,
@@ -1118,11 +1118,20 @@ restore_files(void *arg)
 			}
 		}
 
-		/* open destination file */
-		if (already_exists)
-			out = fio_fopen(to_fullpath, PG_BINARY_R "+", FIO_DB_HOST);
-		else
+		/*
+		 * Open dest file and truncate it to zero, if destination
+		 * file already exists and dest file size is zero, or
+		 * if file do not exist
+		 */
+		if ((already_exists && dest_file->write_size == 0) || !already_exists)
 			out = fio_fopen(to_fullpath, PG_BINARY_W, FIO_DB_HOST);
+		/*
+		 * If file already exists and dest size is not zero,
+		 * then open it for reading and writing.
+		 */
+		else
+			out = fio_fopen(to_fullpath, PG_BINARY_R "+", FIO_DB_HOST);
+
 		if (out == NULL)
 			elog(ERROR, "Cannot open restore target file \"%s\": %s",
 				 to_fullpath, strerror(errno));
@@ -1158,7 +1167,7 @@ restore_files(void *arg)
 			/* disable stdio buffering for local destination nonedata file */
 			if (!fio_is_remote_file(out))
 				setvbuf(out, NULL, _IONBF, BUFSIZ);
-			/* Destination file is non-data file */
+			/* Destination file is nonedata file */
 			arguments->restored_bytes += restore_non_data_file(arguments->parent_chain,
 										arguments->dest_backup, dest_file, out, to_fullpath,
 										already_exists);