MDEV-13564: Refuse MLOG_TRUNCATE in mariabackup

The MySQL 5.7 TRUNCATE TABLE is inherently incompatible
with hot backup, because it is creating and deleting a separate
log file, and it is not writing redo log for all changes of the
InnoDB data dictionary tables. Refuse to create a corrupted backup
if the unsafe form of TRUNCATE was executed.

Note: Undo log tablespace truncation cannot be detected easily.
Also it is incompatible with backup, for similar reasons.

xtrabackup_backup_func(): "Subscribe to" the log events before
the first invocation of xtrabackup_copy_logfile().

recv_parse_or_apply_log_rec_body(): If the function pointer
log_truncate is set, invoke it to report MLOG_TRUNCATE.

extra/mariabackup/xtrabackup.cc

@@ -358,9 +358,8 @@ struct ddl_tracker_t {
 	/* For DDL operation found in redo log,  */
 	space_id_to_name_t id_to_name;
 };
-const space_id_t REMOVED_SPACE_ID = ULINT_MAX;
-static ddl_tracker_t ddl_tracker;
 
+static ddl_tracker_t ddl_tracker;
 
 /* Whether xtrabackup_binlog_info should be created on recovery */
 static bool recover_binlog_info;
@@ -618,9 +617,8 @@ void backup_file_op(ulint space_id, const byte* flags,
 
 
 /** Callback whenever MLOG_INDEX_LOAD happens.
-@param[in]	space_id	space id to check
-@return false */
-void backup_optimized_ddl_op(ulint space_id)
+@param[in]	space_id	space id to check */
+static void backup_optimized_ddl_op(ulint space_id)
 {
 	// TODO : handle incremental
 	if (xtrabackup_incremental)
@@ -631,6 +629,15 @@ void backup_optimized_ddl_op(ulint space_id)
 	pthread_mutex_unlock(&backup_mutex);
 }
 
+/** Callback whenever MLOG_TRUNCATE happens. */
+static void backup_truncate_fail()
+{
+	msg("mariabackup: Incompatible TRUNCATE operation detected.%s\n",
+	    opt_lock_ddl_per_table
+	    ? ""
+	    : " Use --lock-ddl-per-table to lock all tables before backup.");
+}
+
 /* ======== Date copying thread context ======== */
 
 typedef struct {
@@ -4240,12 +4247,13 @@ xtrabackup_backup_func()
 	/* copy log file by current position */
 	log_copy_scanned_lsn = checkpoint_lsn_start;
 	recv_sys->recovered_lsn = log_copy_scanned_lsn;
+	log_optimized_ddl_op = backup_optimized_ddl_op;
+	log_truncate = backup_truncate_fail;
 
 	if (xtrabackup_copy_logfile())
 		goto fail_before_log_copying_thread_start;
 
 	log_copying_stop = os_event_create(0);
-	log_optimized_ddl_op = backup_optimized_ddl_op;
 	os_thread_create(log_copying_thread, NULL, &log_copying_thread_id);
 
 	/* FLUSH CHANGED_PAGE_BITMAPS call */

mysql-test/suite/mariabackup/truncate_during_backup.result

@@ -0,0 +1,4 @@
+CREATE TABLE t1 ENGINE=InnoDB SELECT 1;
+DROP TABLE t1;
+SET GLOBAL innodb_log_checkpoint_now=1;
+SET GLOBAL innodb_log_checkpoint_now=DEFAULT;

mysql-test/suite/mariabackup/truncate_during_backup.test

@@ -0,0 +1,19 @@
+--source include/have_debug.inc
+let $targetdir=$MYSQLTEST_VARDIR/tmp/backup;
+mkdir $targetdir;
+
+CREATE TABLE t1 ENGINE=InnoDB SELECT 1;
+
+--let after_load_tablespaces=TRUNCATE test.t1
+
+--disable_result_log
+--error 1
+exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf  --backup  --target-dir=$targetdir  --dbug=+d,mariabackup_events;
+--enable_result_log
+
+--let after_load_tablespaces=
+
+DROP TABLE t1;
+SET GLOBAL innodb_log_checkpoint_now=1;
+SET GLOBAL innodb_log_checkpoint_now=DEFAULT;
+rmdir $targetdir;

storage/innobase/include/log0recv.h

@@ -153,10 +153,15 @@ bool recv_parse_log_recs(lsn_t checkpoint_lsn, store_t store, bool apply);
 /** Moves the parsing buffer data left to the buffer start. */
 void recv_sys_justify_left_parsing_buf();
 
-/** Report optimized DDL operation (without redo log), corresponding to MLOG_INDEX_LOAD.
+/** Report optimized DDL operation (without redo log),
+corresponding to MLOG_INDEX_LOAD.
 @param[in]	space_id	tablespace identifier
 */
-extern void(*log_optimized_ddl_op)(ulint space_id);
+extern void (*log_optimized_ddl_op)(ulint space_id);
+
+/** Report backup-unfriendly TRUNCATE operation (with separate log file),
+corresponding to MLOG_TRUNCATE. */
+extern void (*log_truncate)();
 
 /** Report an operation to create, delete, or rename a file during backup.
 @param[in]	space_id	tablespace identifier

storage/innobase/log/log0recv.cc

@@ -169,11 +169,16 @@ typedef std::map<
 
 static recv_spaces_t	recv_spaces;
 
-/** Report optimized DDL operation (without redo log), corresponding to MLOG_INDEX_LOAD.
+/** Report optimized DDL operation (without redo log),
+corresponding to MLOG_INDEX_LOAD.
 @param[in]	space_id	tablespace identifier
 */
 void (*log_optimized_ddl_op)(ulint space_id);
 
+/** Report backup-unfriendly TRUNCATE operation (with separate log file),
+corresponding to MLOG_TRUNCATE. */
+void (*log_truncate)();
+
 /** Report an operation to create, delete, or rename a file during backup.
 @param[in]	space_id	tablespace identifier
 @param[in]	flags		tablespace flags (NULL if not create)
@@ -1196,6 +1201,12 @@ recv_parse_or_apply_log_rec_body(
 		}
 		return(ptr + 8);
 	case MLOG_TRUNCATE:
+		if (log_truncate) {
+			ut_ad(srv_operation != SRV_OPERATION_NORMAL);
+			log_truncate();
+			recv_sys->found_corrupt_fs = true;
+			return NULL;
+		}
 		return(truncate_t::parse_redo_entry(ptr, end_ptr, space_id));
 
 	default: