MDEV-13564: Replace innodb_unsafe_truncate with innodb_safe_truncate

Rename the 10.2-specific configuration option innodb_unsafe_truncate
to innodb_safe_truncate, and invert its value.

The default (for now) is innodb_safe_truncate=OFF, to avoid
disrupting users with an undo and redo log format change within
a Generally Available (GA) release series.

mysql-test/suite/gcol/t/innodb_virtual_debug_purge.opt

---skip-innodb-unsafe-truncate
+--loose-innodb-safe-truncate=1

mysql-test/suite/innodb/t/alter_copy.opt

---loose-skip-innodb-unsafe-truncate
+--loose-innodb-safe-truncate=1

mysql-test/suite/innodb/t/alter_crash.opt

 --loose-innodb-sys-tables
---loose-skip-innodb-unsafe-truncate
+--loose-innodb-safe-truncate=1

mysql-test/suite/innodb/t/drop_table_background.opt

---loose-skip-innodb-unsafe-truncate
+--loose-innodb-safe-truncate=1

mysql-test/suite/innodb/t/rename_table_debug.opt

---loose-skip-innodb-unsafe-truncate
+--loose-innodb-safe-truncate=1

mysql-test/suite/innodb/t/truncate.opt

---loose-skip-innodb-unsafe-truncate
+--loose-innodb-safe-truncate=1

mysql-test/suite/innodb/t/truncate_crash.opt

---loose-skip-innodb-unsafe-truncate
+--loose-innodb-safe-truncate=1

mysql-test/suite/innodb/t/truncate_foreign.opt

---loose-skip-innodb-unsafe-truncate
+--loose-innodb-safe-truncate=1

mysql-test/suite/innodb/t/truncate_missing.opt

---loose-skip-innodb-unsafe-truncate
+--loose-innodb-safe-truncate=1

mysql-test/suite/innodb_zip/t/restart.opt

 --loose-innodb-sys-tables
 --loose-innodb-sys-tablespaces
 --loose-innodb-sys-datafiles
---loose-skip-innodb-unsafe-truncate
+--loose-innodb-safe-truncate=1

mysql-test/suite/mariabackup/truncate_during_backup.opt

---loose-skip-innodb-unsafe-truncate
+--loose-innodb-safe-truncate=1

mysql-test/suite/sys_vars/r/sysvars_innodb.result

@@ -2400,6 +2400,20 @@ NUMERIC_BLOCK_SIZE	0
 ENUM_VALUE_LIST	NULL
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	OPTIONAL
+VARIABLE_NAME	INNODB_SAFE_TRUNCATE
+SESSION_VALUE	NULL
+GLOBAL_VALUE	OFF
+GLOBAL_VALUE_ORIGIN	COMPILE-TIME
+DEFAULT_VALUE	OFF
+VARIABLE_SCOPE	GLOBAL
+VARIABLE_TYPE	BOOLEAN
+VARIABLE_COMMENT	Use backup-safe TRUNCATE TABLE and crash-safe RENAME (incompatible with older MariaDB 10.2; OFF by default)
+NUMERIC_MIN_VALUE	NULL
+NUMERIC_MAX_VALUE	NULL
+NUMERIC_BLOCK_SIZE	NULL
+ENUM_VALUE_LIST	OFF,ON
+READ_ONLY	YES
+COMMAND_LINE_ARGUMENT	OPTIONAL
 VARIABLE_NAME	INNODB_SAVED_PAGE_NUMBER_DEBUG
 SESSION_VALUE	NULL
 GLOBAL_VALUE	0
@@ -2974,20 +2988,6 @@ NUMERIC_BLOCK_SIZE	0
 ENUM_VALUE_LIST	NULL
 READ_ONLY	YES
 COMMAND_LINE_ARGUMENT	REQUIRED
-VARIABLE_NAME	INNODB_UNSAFE_TRUNCATE
-SESSION_VALUE	NULL
-GLOBAL_VALUE	ON
-GLOBAL_VALUE_ORIGIN	COMPILE-TIME
-DEFAULT_VALUE	ON
-VARIABLE_SCOPE	GLOBAL
-VARIABLE_TYPE	BOOLEAN
-VARIABLE_COMMENT	Use backup-unsafe TRUNCATE TABLE for compatibility with xtrabackup (on by default)
-NUMERIC_MIN_VALUE	NULL
-NUMERIC_MAX_VALUE	NULL
-NUMERIC_BLOCK_SIZE	NULL
-ENUM_VALUE_LIST	OFF,ON
-READ_ONLY	YES
-COMMAND_LINE_ARGUMENT	OPTIONAL
 VARIABLE_NAME	INNODB_USE_ATOMIC_WRITES
 SESSION_VALUE	NULL
 GLOBAL_VALUE	ON

storage/innobase/handler/ha_innodb.cc

@@ -13452,7 +13452,7 @@ int ha_innobase::truncate()
 
 	update_thd();
 
-	if (srv_57_truncate) {
+	if (!srv_safe_truncate) {
 		if (!trx_is_started(m_prebuilt->trx)) {
 			++m_prebuilt->trx->will_lock;
 		}
@@ -20694,10 +20694,10 @@ static MYSQL_SYSVAR_BOOL(read_only, srv_read_only_mode,
   "Start InnoDB in read only mode (off by default)",
   NULL, NULL, FALSE);
 
-static MYSQL_SYSVAR_BOOL(unsafe_truncate, srv_57_truncate,
+static MYSQL_SYSVAR_BOOL(safe_truncate, srv_safe_truncate,
   PLUGIN_VAR_OPCMDARG | PLUGIN_VAR_READONLY,
-  "Use backup-unsafe TRUNCATE TABLE for compatibility with xtrabackup (on by default)",
-  NULL, NULL, TRUE);
+  "Use backup-safe TRUNCATE TABLE and crash-safe RENAME (incompatible with older MariaDB 10.2; OFF by default)",
+  NULL, NULL, FALSE);
 
 static MYSQL_SYSVAR_BOOL(cmp_per_index_enabled, srv_cmp_per_index_enabled,
   PLUGIN_VAR_OPCMDARG,
@@ -21078,7 +21078,7 @@ static struct st_mysql_sys_var* innobase_system_variables[]= {
   MYSQL_SYSVAR(random_read_ahead),
   MYSQL_SYSVAR(read_ahead_threshold),
   MYSQL_SYSVAR(read_only),
-  MYSQL_SYSVAR(unsafe_truncate),
+  MYSQL_SYSVAR(safe_truncate),
   MYSQL_SYSVAR(io_capacity),
   MYSQL_SYSVAR(io_capacity_max),
   MYSQL_SYSVAR(page_cleaners),

storage/innobase/include/srv0srv.h

@@ -256,9 +256,9 @@ extern my_bool	high_level_read_only;
 /** store to its own file each table created by an user; data
 dictionary tables are in the system tablespace 0 */
 extern my_bool	srv_file_per_table;
-/** whether to use the MySQL 5.7 WL#6501 TRUNCATE TABLE implementation
-that does not work with backup */
-extern my_bool	srv_57_truncate;
+/** whether to use backup-safe TRUNCATE and crash-safe RENAME
+instead of the MySQL 5.7 WL#6501 TRUNCATE TABLE implementation */
+extern my_bool	srv_safe_truncate;
 /** Sleep delay for threads waiting to enter InnoDB. In micro-seconds. */
 extern	ulong	srv_thread_sleep_delay;
 /** Maximum sleep delay (in micro-seconds), value of 0 disables it.*/

storage/innobase/log/log0log.cc

@@ -790,15 +790,15 @@ log_init(ulint n_files)
 	log_group_t*	group = &log_sys->log;
 
 	group->n_files = n_files;
-	group->subformat = !srv_57_truncate;
-	if (srv_57_truncate) {
-		group->format = srv_encrypt_log
-			? LOG_HEADER_FORMAT_10_2 | LOG_HEADER_FORMAT_ENCRYPTED
-			: LOG_HEADER_FORMAT_10_2;
-	} else {
+	group->subformat = srv_safe_truncate;
+	if (srv_safe_truncate) {
 		group->format = srv_encrypt_log
 			? LOG_HEADER_FORMAT_10_3 | LOG_HEADER_FORMAT_ENCRYPTED
 			: LOG_HEADER_FORMAT_10_3;
+	} else {
+		group->format = srv_encrypt_log
+			? LOG_HEADER_FORMAT_10_2 | LOG_HEADER_FORMAT_ENCRYPTED
+			: LOG_HEADER_FORMAT_10_2;
 	}
 	group->file_size = srv_log_file_size;
 	group->state = LOG_GROUP_OK;
@@ -881,15 +881,15 @@ log_group_file_header_flush(
 	ut_ad(!recv_no_log_write);
 	ut_a(nth_file < group->n_files);
 	ut_ad((group->format & ~LOG_HEADER_FORMAT_ENCRYPTED)
-	      == (srv_57_truncate
-		  ? LOG_HEADER_FORMAT_10_2
-		  : LOG_HEADER_FORMAT_10_3));
+	      == (srv_safe_truncate
+		  ? LOG_HEADER_FORMAT_10_3
+		  : LOG_HEADER_FORMAT_10_2));
 
 	buf = *(group->file_header_bufs + nth_file);
 
 	memset(buf, 0, OS_FILE_LOG_BLOCK_SIZE);
 	mach_write_to_4(buf + LOG_HEADER_FORMAT, group->format);
-	mach_write_to_4(buf + LOG_HEADER_SUBFORMAT, !srv_57_truncate);
+	mach_write_to_4(buf + LOG_HEADER_SUBFORMAT, srv_safe_truncate);
 	mach_write_to_8(buf + LOG_HEADER_START_LSN, start_lsn);
 	strcpy(reinterpret_cast<char*>(buf) + LOG_HEADER_CREATOR,
 	       LOG_HEADER_CREATOR_CURRENT);

storage/innobase/log/log0recv.cc

@@ -3769,7 +3769,7 @@ recv_recovery_rollback_active(void)
 		/* Drop partially created indexes. */
 		row_merge_drop_temp_indexes();
 		/* Drop garbage tables. */
-		if (!srv_57_truncate)
+		if (srv_safe_truncate)
 		row_mysql_drop_garbage_tables();
 
 		/* Drop any auxiliary tables that were not dropped when the

storage/innobase/row/row0mysql.cc

@@ -4403,7 +4403,7 @@ row_rename_table_for_mysql(
 		goto funct_exit;
 	}
 
-	if (!table->is_temporary() && !srv_57_truncate) {
+	if (!table->is_temporary() && srv_safe_truncate) {
 		err = trx_undo_report_rename(trx, table);
 
 		if (err != DB_SUCCESS) {

storage/innobase/srv/srv0srv.cc

@@ -152,9 +152,9 @@ my_bool	srv_read_only_mode;
 /** store to its own file each table created by an user; data
 dictionary tables are in the system tablespace 0 */
 my_bool	srv_file_per_table;
-/** whether to use the MySQL 5.7 WL#6501 TRUNCATE TABLE implementation
-that does not work with backup */
-my_bool	srv_57_truncate;
+/** whether to use backup-safe TRUNCATE and crash-safe RENAME
+instead of the MySQL 5.7 WL#6501 TRUNCATE TABLE implementation */
+my_bool	srv_safe_truncate;
 /** The file format to use on new *.ibd files. */
 ulint	srv_file_format;
 /** Whether to check file format during startup.  A value of

storage/innobase/srv/srv0start.cc

@@ -1393,15 +1393,15 @@ srv_prepare_to_delete_redo_log_files(
 	ulint	pending_io = 0;
 	ulint	count = 0;
 
-	if (srv_57_truncate) {
+	if (srv_safe_truncate) {
 		if ((log_sys->log.format & ~LOG_HEADER_FORMAT_ENCRYPTED)
-		    != LOG_HEADER_FORMAT_10_2) {
+		    != LOG_HEADER_FORMAT_10_3
+		    || log_sys->log.subformat != 1) {
 			srv_log_file_size = 0;
 		}
 	} else {
 		if ((log_sys->log.format & ~LOG_HEADER_FORMAT_ENCRYPTED)
-		    != LOG_HEADER_FORMAT_10_3
-		    || log_sys->log.subformat != 1) {
+		    != LOG_HEADER_FORMAT_10_2) {
 			srv_log_file_size = 0;
 		}
 	}
@@ -2399,16 +2399,16 @@ innobase_start_or_create_for_mysql()
 		} else if (srv_log_file_size_requested == srv_log_file_size
 			   && srv_n_log_files_found == srv_n_log_files
 			   && log_sys->log.format
-			   == (srv_57_truncate
+			   == (srv_safe_truncate
 			       ? (srv_encrypt_log
-				  ? LOG_HEADER_FORMAT_10_2
+				  ? LOG_HEADER_FORMAT_10_3
 				  | LOG_HEADER_FORMAT_ENCRYPTED
-				  : LOG_HEADER_FORMAT_10_2)
+				  : LOG_HEADER_FORMAT_10_3)
 			       : (srv_encrypt_log
-				  ? LOG_HEADER_FORMAT_10_3
+				  ? LOG_HEADER_FORMAT_10_2
 				  | LOG_HEADER_FORMAT_ENCRYPTED
-				  : LOG_HEADER_FORMAT_10_3))
-			   && log_sys->log.subformat == !srv_57_truncate) {
+				  : LOG_HEADER_FORMAT_10_2))
+			   && log_sys->log.subformat == srv_safe_truncate) {
 			/* No need to add or remove encryption,
 			upgrade, downgrade, or resize. */
 		} else {

storage/innobase/trx/trx0rec.cc

@@ -1938,7 +1938,7 @@ trx_undo_report_rename(trx_t* trx, const dict_table_t* table)
 	ut_ad(!trx->read_only);
 	ut_ad(trx->id);
 	ut_ad(!table->is_temporary());
-	ut_ad(!srv_57_truncate);
+	ut_ad(srv_safe_truncate);
 
 	trx_rseg_t*	rseg	= trx->rsegs.m_redo.rseg;
 	trx_undo_t**	pundo	= &trx->rsegs.m_redo.insert_undo;