InnoDB: Implement fast TRUNCATE TABLE (Bug #7150)

innobase/dict/dict0boot.c:
  Added DICT_SYS_INDEXES_TYPE_FIELD
innobase/dict/dict0crea.c:
  Added dict_truncate_index_tree()
innobase/include/dict0boot.h:
  Added DICT_SYS_INDEXES_TYPE_FIELD
innobase/include/dict0crea.h:
  Added dict_truncate_index_tree()
innobase/include/row0mysql.h:
  Added row_truncate_table_for_mysql()
innobase/row/row0mysql.c:
  Added row_truncate_table_for_mysql()
sql/ha_innodb.cc:
  Added ha_innobase::delete_all_rows() in order to
  implement fast TRUNCATE TABLE
sql/ha_innodb.h:
  Added ha_innobase::delete_all_rows() in order to
  implement fast TRUNCATE TABLE

innobase/dict/dict0boot.c

@@ -332,6 +332,9 @@ dict_boot(void)
 #endif
 #if DICT_SYS_INDEXES_SPACE_NO_FIELD != 5 + 2
 #error "DICT_SYS_INDEXES_SPACE_NO_FIELD != 5 + 2"
+#endif
+#if DICT_SYS_INDEXES_TYPE_FIELD != 4 + 2
+#error "DICT_SYS_INDEXES_TYPE_FIELD != 4 + 2"
 #endif
 
 	table->id = DICT_INDEXES_ID;

innobase/dict/dict0crea.c

@@ -706,6 +706,101 @@ dict_drop_index_tree(
 				DICT_SYS_INDEXES_PAGE_NO_FIELD, FIL_NULL, mtr);
 }
 
+/***********************************************************************
+Truncates the index tree associated with a row in SYS_INDEXES table. */
+
+void
+dict_truncate_index_tree(
+/*=====================*/
+	dict_table_t*	table,	/* in: the table the index belongs to */
+	rec_t*		rec,	/* in: record in the clustered index of
+				SYS_INDEXES table */
+	mtr_t*		mtr)	/* in: mtr having the latch
+				on the record page */
+{
+	ulint		root_page_no;
+	ulint		space;
+	ulint		type;
+	dulint		index_id;
+	byte*		ptr;
+	ulint		len;
+	ibool		comp;
+	dict_index_t*	index;
+
+#ifdef UNIV_SYNC_DEBUG
+	ut_ad(mutex_own(&(dict_sys->mutex)));
+#endif /* UNIV_SYNC_DEBUG */
+
+	ut_a(!dict_sys->sys_indexes->comp);
+	ptr = rec_get_nth_field_old(rec, DICT_SYS_INDEXES_PAGE_NO_FIELD, &len);
+
+	ut_ad(len == 4);
+
+	root_page_no = mtr_read_ulint(ptr, MLOG_4BYTES, mtr);
+
+	if (root_page_no == FIL_NULL) {
+		/* The tree has been freed. */
+
+		return;
+	}
+
+	ptr = rec_get_nth_field_old(rec,
+				DICT_SYS_INDEXES_SPACE_NO_FIELD, &len);
+
+	ut_ad(len == 4);
+
+	space = mtr_read_ulint(ptr, MLOG_4BYTES, mtr);
+
+	if (!fil_tablespace_exists_in_mem(space)) {
+		/* It is a single table tablespace and the .ibd file is
+		missing: do nothing */
+
+		return;
+	}
+
+	ptr = rec_get_nth_field_old(rec,
+				DICT_SYS_INDEXES_TYPE_FIELD, &len);
+	ut_ad(len == 4);
+	type = mach_read_from_4(ptr);
+
+	ptr = rec_get_nth_field_old(rec, 1, &len);
+	ut_ad(len == 8);
+	index_id = mach_read_from_8(ptr);
+
+	/* We free all the pages but the root page first; this operation
+	may span several mini-transactions */
+
+	btr_free_but_not_root(space, root_page_no);
+
+	/* Then we free the root page in the same mini-transaction where
+	we create the b-tree and write its new root page number to the
+	appropriate field in the SYS_INDEXES record: this mini-transaction
+	marks the B-tree totally truncated */
+
+	comp = page_is_comp(btr_page_get(
+				space, root_page_no, RW_X_LATCH, mtr));
+
+	btr_free_root(space, root_page_no, mtr);
+
+	/* Find the index corresponding to this SYS_INDEXES record. */
+	for (index = UT_LIST_GET_FIRST(table->indexes);
+			index;
+			index = UT_LIST_GET_NEXT(indexes, index)) {
+		if (!ut_dulint_cmp(index->id, index_id)) {
+			break;
+		}
+	}
+
+	root_page_no = btr_create(type, space, index_id, comp, mtr);
+	if (index) {
+		index->page_no = root_page_no;
+	}
+
+	page_rec_write_index_page_no(rec,
+				DICT_SYS_INDEXES_PAGE_NO_FIELD,
+				root_page_no, mtr);
+}
+
 /*************************************************************************
 Creates a table create graph. */
 

innobase/include/dict0boot.h

@@ -119,6 +119,7 @@ dict_create(void);
 clustered index */
 #define DICT_SYS_INDEXES_PAGE_NO_FIELD	 8
 #define DICT_SYS_INDEXES_SPACE_NO_FIELD	 7
+#define DICT_SYS_INDEXES_TYPE_FIELD	 6
 					
 /* When a row id which is zero modulo this number (which must be a power of
 two) is assigned, the field DICT_HDR_ROW_ID on the dictionary header page is

innobase/include/dict0crea.h

@@ -54,6 +54,17 @@ dict_create_index_step(
 				/* out: query thread to run next or NULL */
 	que_thr_t*	thr);	/* in: query thread */
 /***********************************************************************
+Truncates the index tree associated with a row in SYS_INDEXES table. */
+
+void
+dict_truncate_index_tree(
+/*=====================*/
+	dict_table_t*	table,	/* in: the table the index belongs to */
+	rec_t*		rec,	/* in: record in the clustered index of
+				SYS_INDEXES table */
+	mtr_t*		mtr);	/* in: mtr having the latch
+				on the record page */
+/***********************************************************************
 Drops the index tree associated with a row in SYS_INDEXES table. */
 
 void

innobase/include/row0mysql.h

@@ -363,6 +363,15 @@ row_get_background_drop_list_len_low(void);
 /*======================================*/
 					/* out: how many tables in list */
 /*************************************************************************
+Truncates a table for MySQL. */
+
+int
+row_truncate_table_for_mysql(
+/*=========================*/
+				/* out: error code or DB_SUCCESS */
+	dict_table_t*	table,	/* in: table handle */
+	trx_t*		trx);	/* in: transaction handle */
+/*************************************************************************
 Drops a table for MySQL. If the name of the dropped table ends to
 characters INNODB_MONITOR, then this also stops printing of monitor
 output by the master thread. */

innobase/row/row0mysql.c

@@ -2421,6 +2421,285 @@ funct_exit:
 	return((int) err);
 }
 
+/*************************************************************************
+Truncates a table for MySQL. */
+
+int
+row_truncate_table_for_mysql(
+/*=========================*/
+				/* out: error code or DB_SUCCESS */
+	dict_table_t*	table,	/* in: table handle */
+	trx_t*		trx)	/* in: transaction handle */
+{
+	dict_foreign_t*	foreign;
+	ulint		err;
+	ibool		locked_dictionary	= FALSE;
+	mem_heap_t*	heap;
+	byte*		buf;
+	dtuple_t*	tuple;
+	dfield_t*	dfield;
+	dict_index_t*	sys_index;
+	btr_pcur_t	pcur;
+	mtr_t		mtr;
+	dulint		new_id;
+	char*		sql;
+	que_thr_t*	thr;
+	que_t*		graph			= NULL;
+
+/* How do we prevent crashes caused by ongoing operations on the table? Old
+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.
+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.
+3) Insert buffer: we remove all entries for the table in the insert
+buffer tree; ... TODO
+4) Linear readahead and random readahead: we use the same method as in 3) to
+discard ongoing operations.
+5) FOREIGN KEY operations: if table->n_foreign_key_checks_running > 0, we
+do not allow the discard. We also reserve the data dictionary latch. */
+
+	static const char renumber_tablespace_proc[] =
+	"PROCEDURE RENUMBER_TABLESPACE_PROC () IS\n"
+	"old_id CHAR;\n"
+	"new_id CHAR;\n"
+	"old_id_low INT;\n"
+	"old_id_high INT;\n"
+	"new_id_low INT;\n"
+	"new_id_high INT;\n"
+	"BEGIN\n"
+	"old_id_high := %lu;\n"
+	"old_id_low := %lu;\n"
+	"new_id_high := %lu;\n"
+	"new_id_low := %lu;\n"
+   "old_id := CONCAT(TO_BINARY(old_id_high, 4), TO_BINARY(old_id_low, 4));\n"
+   "new_id := CONCAT(TO_BINARY(new_id_high, 4), TO_BINARY(new_id_low, 4));\n"
+	"UPDATE SYS_TABLES SET ID = new_id\n"
+	"WHERE ID = old_id;\n"
+	"UPDATE SYS_COLUMNS SET TABLE_ID = new_id\n"
+	"WHERE TABLE_ID = old_id;\n"
+	"UPDATE SYS_INDEXES SET TABLE_ID = new_id\n"
+	"WHERE TABLE_ID = old_id;\n"
+	"COMMIT WORK;\n"
+	"END;\n";
+
+	ut_ad(trx->mysql_thread_id == os_thread_get_curr_id());
+	ut_ad(table);
+
+	if (srv_created_new_raw) {
+		fputs(
+		"InnoDB: A new raw disk partition was initialized or\n"
+		"InnoDB: innodb_force_recovery is on: we do not allow\n"
+		"InnoDB: database modifications by the user. Shut down\n"
+		"InnoDB: mysqld and edit my.cnf so that newraw is replaced\n"
+		"InnoDB: with raw, and innodb_force_... is removed.\n",
+                stderr);
+
+		return(DB_ERROR);
+	}
+
+	trx->op_info = "truncating table";
+
+	trx_start_if_not_started(trx);
+
+	/* Serialize data dictionary operations with dictionary mutex:
+	no deadlocks can occur then in these operations */
+
+	if (trx->dict_operation_lock_mode != RW_X_LATCH) {
+		/* 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));
+#endif /* UNIV_SYNC_DEBUG */
+
+	/* Check if the table is referenced by foreign key constraints from
+	some other table (not the table itself) */
+
+	foreign = UT_LIST_GET_FIRST(table->referenced_list);
+
+	while (foreign && foreign->foreign_table == table) {
+		foreign = UT_LIST_GET_NEXT(referenced_list, foreign);
+	}
+
+	if (foreign && trx->check_foreigns) {
+		FILE*	ef	= dict_foreign_err_file;
+
+		/* We only allow truncating a referenced table if
+		FOREIGN_KEY_CHECKS is set to 0 */
+
+		mutex_enter(&dict_foreign_err_mutex);
+		rewind(ef);
+		ut_print_timestamp(ef);
+
+		fputs("  Cannot truncate table ", ef);
+		ut_print_name(ef, trx, table->name);
+		fputs("\n"
+			"because it is referenced by ", ef);
+		ut_print_name(ef, trx, foreign->foreign_table_name);
+		putc('\n', ef);
+		mutex_exit(&dict_foreign_err_mutex);
+
+		err = DB_ERROR;
+		goto funct_exit;
+	}
+
+	if (table->n_mysql_handles_opened > 1) {
+		ut_print_timestamp(stderr);
+fputs("	 InnoDB: Warning: MySQL is trying to truncate table ", stderr);
+		ut_print_name(stderr, trx, table->name);
+		fputs("\n"
+"InnoDB: though there are still open handles to it.\n", stderr);
+		err = DB_ERROR;
+
+		goto funct_exit;
+	}
+
+	/* TODO: could we replace the counter n_foreign_key_checks_running
+	with lock checks on the table? Acquire here an exclusive lock on the
+	table, and rewrite lock0lock.c and the lock wait in srv0srv.c so that
+	they can cope with the table having been truncated here? Foreign key
+	checks take an IS or IX lock on the table. */
+
+	if (table->n_foreign_key_checks_running > 0) {
+		ut_print_timestamp(stderr);
+		fputs("	 InnoDB: You are trying to truncate table ", stderr);
+		ut_print_name(stderr, trx, table->name);
+		fputs("\n"
+"InnoDB: though there is a foreign key check running on it.\n",
+			stderr);
+		err = DB_ERROR;
+
+		goto funct_exit;
+	}
+
+	/* Remove any locks there are on the table or its records */
+
+	lock_reset_all_on_table(table);
+
+	trx->dict_operation = TRUE;
+	trx->table_id = table->id;
+
+	/* scan SYS_INDEXES for all indexes of the table */
+	heap = mem_heap_create(800);
+
+	tuple = dtuple_create(heap, 1);
+	dfield = dtuple_get_nth_field(tuple, 0);
+
+	buf = mem_heap_alloc(heap, 8);
+	mach_write_to_8(buf, table->id);
+
+	dfield_set_data(dfield, buf, 8);
+	sys_index = dict_table_get_first_index(dict_sys->sys_indexes);
+	dict_index_copy_types(tuple, sys_index, 1);
+
+	mtr_start(&mtr);
+	btr_pcur_open_on_user_rec(sys_index, tuple, PAGE_CUR_GE,
+						BTR_MODIFY_LEAF, &pcur, &mtr);
+	for (;;) {
+		rec_t*		rec;
+		const byte*	field;
+		ulint		len;
+
+		if (!btr_pcur_is_on_user_rec(&pcur, &mtr)) {
+			/* The end of SYS_INDEXES has been reached. */
+			break;
+		}
+
+		rec = btr_pcur_get_rec(&pcur);
+
+		field = rec_get_nth_field_old(rec, 0, &len);
+		ut_ad(len == 8);
+
+		if (memcmp(buf, field, len) != 0) {
+			/* End of indexes for the table (TABLE_ID mismatch). */
+			break;
+		}
+
+		if (rec_get_deleted_flag(rec, FALSE)) {
+			/* The index has been dropped. */
+			continue;
+		}
+
+		dict_truncate_index_tree(table, rec, &mtr);
+
+		btr_pcur_move_to_next_user_rec(&pcur, &mtr);
+	}
+
+	btr_pcur_close(&pcur);
+	mtr_commit(&mtr);
+
+	new_id = dict_hdr_get_new_id(DICT_HDR_TABLE_ID);
+
+	mem_heap_empty(heap);
+	sql = mem_heap_alloc(heap, (sizeof renumber_tablespace_proc) + 40);
+	sprintf(sql, renumber_tablespace_proc,
+		(ulong) ut_dulint_get_high(table->id),
+		(ulong) ut_dulint_get_low(table->id),
+		(ulong) ut_dulint_get_high(new_id),
+		(ulong) ut_dulint_get_low(new_id));
+
+	graph = pars_sql(sql);
+
+	ut_a(graph);
+
+	mem_heap_free(heap);
+
+	graph->trx = trx;
+	trx->graph = NULL;
+
+	graph->fork_type = QUE_FORK_MYSQL_INTERFACE;
+
+	thr = que_fork_start_command(graph);
+	ut_a(thr);
+
+	que_run_threads(thr);
+
+	que_graph_free(graph);
+
+	err = trx->error_state;
+
+	if (err != DB_SUCCESS) {
+		trx->error_state = DB_SUCCESS;
+		trx_general_rollback_for_mysql(trx, FALSE, NULL);
+		trx->error_state = DB_SUCCESS;
+		ut_print_timestamp(stderr);
+fputs("	 InnoDB: Unable to assign a new identifier to table ", stderr);
+		ut_print_name(stderr, trx, table->name);
+		fputs("\n"
+"InnoDB: after truncating it.  Background processes may corrupt the table!\n",
+			stderr);
+		err = DB_ERROR;
+	} else {
+		dict_table_change_id_in_cache(table, new_id);
+	}
+
+	dict_update_statistics(table);
+
+  	trx_commit_for_mysql(trx);
+
+funct_exit:
+
+	if (locked_dictionary) {
+		row_mysql_unlock_data_dictionary(trx);
+	}
+
+	trx->op_info = "";
+
+	srv_wake_master_thread();
+
+	return((int) err);
+}
+
 /*************************************************************************
 Drops a table for MySQL. If the name of the table to be dropped is equal
 with one of the predefined magic table names, then this also stops printing

sql/ha_innodb.cc

@@ -4080,6 +4080,48 @@ ha_innobase::discard_or_import_tablespace(
 	DBUG_RETURN(err);
 }
 
+/*********************************************************************
+Deletes all rows of an InnoDB table. */
+
+int
+ha_innobase::delete_all_rows(void)
+/*==============================*/
+				/* out: error number */
+{
+	row_prebuilt_t*	prebuilt	= (row_prebuilt_t*)innobase_prebuilt;
+	int		error;
+	trx_t*		trx;
+	THD*		thd		= current_thd;
+
+	DBUG_ENTER("ha_innobase::delete_all_rows");
+
+	if (thd->lex->sql_command != SQLCOM_TRUNCATE) {
+	fallback:
+		/* We only handle TRUNCATE TABLE t as a special case.
+		DELETE FROM t will have to use ha_innobase::delete_row(). */
+		DBUG_RETURN(my_errno=HA_ERR_WRONG_COMMAND);
+	}
+
+	/* Get the transaction associated with the current thd, or create one
+	if not yet created */
+
+	trx = check_trx_exists(thd);
+
+	/* Truncate the table in InnoDB */
+
+	error = row_truncate_table_for_mysql(prebuilt->table, trx);
+	if (error == DB_ERROR) {
+		/* Cannot truncate; resort to ha_innobase::delete_row() */
+		goto fallback;
+	}
+
+	innobase_commit_low(trx);
+
+	error = convert_error_code_to_mysql(error, NULL);
+
+	DBUG_RETURN(error);
+}
+
 /*********************************************************************
 Drops a table from an InnoDB database. Before calling this function,
 MySQL calls innobase_commit to commit the transaction of the current user.

sql/ha_innodb.h

@@ -159,6 +159,7 @@ class ha_innobase: public handler
 
   	int create(const char *name, register TABLE *form,
 					HA_CREATE_INFO *create_info);
+	int delete_all_rows();
   	int delete_table(const char *name);
 	int rename_table(const char* from, const char* to);
 	int check(THD* thd, HA_CHECK_OPT* check_opt);