InnoDB: Cleanups of TRUNCATE TABLE code

innobase/row/row0mysql.c

@@ -2433,7 +2433,6 @@ row_truncate_table_for_mysql(
 {
 	dict_foreign_t*	foreign;
 	ulint		err;
-	ibool		locked_dictionary	= FALSE;
 	mem_heap_t*	heap;
 	byte*		buf;
 	dtuple_t*	tuple;
@@ -2451,7 +2450,9 @@ operations could try to access non-existent pages.
 
 1) SQL queries, INSERT, SELECT, ...: we must get an exclusive MySQL table lock
 on the table before we can do TRUNCATE TABLE. Then there are no running
-queries on the table.
+queries on the table. This is guaranteed, because in
+ha_innobase::store_lock(), we do not weaken the TL_WRITE lock requested
+by MySQL when executing SQLCOM_TRUNCATE.
 2) Purge and rollback: we assign a new table id for the table. Since purge and
 rollback look for the table based on the table id, they see the table as
 'dropped' and discard their operations.
@@ -2516,15 +2517,12 @@ do not allow the TRUNCATE.  We also reserve the data dictionary latch. */
 	/* Serialize data dictionary operations with dictionary mutex:
 	no deadlocks can occur then in these operations */
 
-	if (trx->dict_operation_lock_mode != RW_X_LATCH) {
+	ut_a(trx->dict_operation_lock_mode == 0);
 	/* Prevent foreign key checks etc. while we are truncating the
 	table */
 
 	row_mysql_lock_data_dictionary(trx);
 
-		locked_dictionary = TRUE;
-	}
-
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&(dict_sys->mutex)));
 	ut_ad(rw_lock_own(&dict_operation_lock, RW_LOCK_EX));
@@ -2551,8 +2549,8 @@ do not allow the TRUNCATE.  We also reserve the data dictionary latch. */
 
 		fputs("  Cannot truncate table ", ef);
 		ut_print_name(ef, trx, table->name);
-		fputs("\n"
-			"because it is referenced by ", ef);
+		fputs(" by DROP+CREATE\n"
+			"InnoDB: because it is referenced by ", ef);
 		ut_print_name(ef, trx, foreign->foreign_table_name);
 		putc('\n', ef);
 		mutex_exit(&dict_foreign_err_mutex);
@@ -2569,10 +2567,10 @@ do not allow the TRUNCATE.  We also reserve the data dictionary latch. */
 
 	if (table->n_foreign_key_checks_running > 0) {
 		ut_print_timestamp(stderr);
-		fputs("	 InnoDB: You are trying to truncate table ", stderr);
+		fputs("	 InnoDB: Cannot truncate table ", stderr);
 		ut_print_name(stderr, trx, table->name);
-		fputs("\n"
-"InnoDB: though there is a foreign key check running on it.\n",
+		fputs(" by DROP+CREATE\n"
+"InnoDB: because there is a foreign key check running on it.\n",
 			stderr);
 		err = DB_ERROR;
 
@@ -2686,9 +2684,7 @@ fputs("	 InnoDB: Unable to assign a new identifier to table ", stderr);
 
 funct_exit:
 
-	if (locked_dictionary) {
 	row_mysql_unlock_data_dictionary(trx);
-	}
 
 	trx->op_info = "";
 

sql/ha_innodb.cc

@@ -4128,7 +4128,7 @@ ha_innobase::delete_all_rows(void)
 		goto fallback;
 	}
 
-	innobase_commit_low(trx);
+	innobase_commit(thd, trx);
 
 	error = convert_error_code_to_mysql(error, NULL);