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

8 files changed, 441 insertions, 0 deletions

diff --git a/innobase/dict/dict0boot.c b/innobase/dict/dict0boot.c
index e500b92252f..883c5464319 100644
--- a/innobase/dict/dict0boot.c
+++ b/innobase/dict/dict0boot.c
@@ -333,6 +333,9 @@ dict_boot(void)
 #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;
 	dict_table_add_to_cache(table);
diff --git a/innobase/dict/dict0crea.c b/innobase/dict/dict0crea.c
index 747a99ebdc9..e744ffda7a6 100644
--- a/innobase/dict/dict0crea.c
+++ b/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. */
 
diff --git a/innobase/include/dict0boot.h b/innobase/include/dict0boot.h
index 35eff5af29a..86702cbca05 100644
--- a/innobase/include/dict0boot.h
+++ b/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
diff --git a/innobase/include/dict0crea.h b/innobase/include/dict0crea.h
index 8b6944fc605..d718e92eb13 100644
--- a/innobase/include/dict0crea.h
+++ b/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
diff --git a/innobase/include/row0mysql.h b/innobase/include/row0mysql.h
index bd5ad3adba5..1618df02499 100644
--- a/innobase/include/row0mysql.h
+++ b/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. */
diff --git a/innobase/row/row0mysql.c b/innobase/row/row0mysql.c
index 380fcf236ed..67477b36a05 100644
--- a/innobase/row/row0mysql.c
+++ b/innobase/row/row0mysql.c
@@ -2422,6 +2422,285 @@ funct_exit:
 }
 
 /*************************************************************************
+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
 the corresponding monitor output by the master thread. */
diff --git a/sql/ha_innodb.cc b/sql/ha_innodb.cc
index 0bca8c21715..9452723110f 100644
--- a/sql/ha_innodb.cc
+++ b/sql/ha_innodb.cc
@@ -4081,6 +4081,48 @@ ha_innobase::discard_or_import_tablespace(
 }
 
 /*********************************************************************
+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.
 Then the current user cannot have locks set on the table. Drop table
diff --git a/sql/ha_innodb.h b/sql/ha_innodb.h
index fcb9165de64..437a33116d7 100644
--- a/sql/ha_innodb.h
+++ b/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);