Bug#49938: Failing assertion: inode or deadlock in fsp/fsp0fsp.c

Bug#54678: InnoDB, TRUNCATE, ALTER, I_S SELECT, crash or deadlock

- Incompatible change: truncate no longer resorts to a row by
row delete if the storage engine does not support the truncate
method. Consequently, the count of affected rows does not, in
any case, reflect the actual number of rows.

- Incompatible change: it is no longer possible to truncate a
table that participates as a parent in a foreign key constraint,
unless it is a self-referencing constraint (both parent and child
are in the same table). To work around this incompatible change
and still be able to truncate such tables, disable foreign checks
with SET foreign_key_checks=0 before truncate. Alternatively, if
foreign key checks are necessary, please use a DELETE statement
without a WHERE condition.

Problem description:

The problem was that for storage engines that do not support
truncate table via a external drop and recreate, such as InnoDB
which implements truncate via a internal drop and recreate, the
delete_all_rows method could be invoked with a shared metadata
lock, causing problems if the engine needed exclusive access
to some internal metadata. This problem originated with the
fact that there is no truncate specific handler method, which
ended up leading to a abuse of the delete_all_rows method that
is primarily used for delete operations without a condition.

Solution:

The solution is to introduce a truncate handler method that is
invoked when the engine does not support truncation via a table
drop and recreate. This method is invoked under a exclusive
metadata lock, so that there is only a single instance of the
table when the method is invoked.

Also, the method is not invoked and a error is thrown if
the table is a parent in a non-self-referencing foreign key
relationship. This was necessary to avoid inconsistency as
some integrity checks are bypassed. This is inline with the
fact that truncate is primarily a DDL operation that was
designed to quickly remove all data from a table.

3 files changed, 28 insertions, 4 deletions

diff --git a/mysql-test/r/mdl_sync.result b/mysql-test/r/mdl_sync.result
index de57e3859b7..d2a32c25201 100644
--- a/mysql-test/r/mdl_sync.result
+++ b/mysql-test/r/mdl_sync.result
@@ -2632,7 +2632,8 @@ DROP TABLE IF EXISTS t1;
 CREATE TABLE t1 (a INT) ENGINE=InnoDB;
 INSERT INTO t1 VALUES (1),(2),(3);
 # Connection: con1
-SET debug_sync='lock_table_for_truncate SIGNAL parked_truncate WAIT_FOR go_truncate';
+LOCK TABLES t1 WRITE;
+SET debug_sync='upgrade_lock_for_truncate SIGNAL parked_truncate WAIT_FOR go_truncate';
 TRUNCATE TABLE t1;
 # Connection: default
 SET debug_sync='now WAIT_FOR parked_truncate';
@@ -2647,10 +2648,11 @@ FLUSH TABLES t1;
 # Connection: default
 SET debug_sync='now WAIT_FOR parked_flush';
 SET debug_sync='now SIGNAL go_truncate';
-# Connection: con1
-# Reaping...
-# Connection: default
+# Ensure that truncate waits for a exclusive lock
 SET debug_sync= 'now SIGNAL go_show';
+# Connection: con1 (TRUNCATE)
+# Reaping...
+UNLOCK TABLES;
 # Connection: con2 (SHOW FIELDS FROM t1)
 # Reaping...
 Field	Type	Null	Key	Default	Extra
diff --git a/mysql-test/r/sp_trans.result b/mysql-test/r/sp_trans.result
index 4fa91121f50..4163725a196 100644
--- a/mysql-test/r/sp_trans.result
+++ b/mysql-test/r/sp_trans.result
@@ -585,3 +585,20 @@ UPDATE t1_aux SET f2 = 2 WHERE f1 = f1_two_inserts()|
 ERROR 23000: Column 'f2' cannot be null
 DROP TABLE t1_aux, t1_not_null|
 DROP FUNCTION f1_two_inserts|
+#
+# Bug#49938: Failing assertion: inode or deadlock in fsp/fsp0fsp.c
+#
+DROP PROCEDURE IF EXISTS p1|
+DROP TABLE IF EXISTS t1|
+CREATE TABLE t1 (a INT) ENGINE=INNODB|
+CREATE PROCEDURE p1()
+BEGIN
+TRUNCATE TABLE t1;
+END|
+LOCK TABLES t1 WRITE|
+CALL p1()|
+FLUSH TABLES;
+UNLOCK TABLES|
+CALL p1()|
+DROP PROCEDURE p1|
+DROP TABLE t1|
diff --git a/mysql-test/r/trigger-trans.result b/mysql-test/r/trigger-trans.result
index 2c4e355af9d..722ac79854d 100644
--- a/mysql-test/r/trigger-trans.result
+++ b/mysql-test/r/trigger-trans.result
@@ -151,9 +151,14 @@ CREATE TRIGGER t1_ad AFTER DELETE ON t1 FOR EACH ROW SET @b = 1;
 SET @a = 0;
 SET @b = 0;
 TRUNCATE t1;
+ERROR 42000: Cannot truncate a table referenced in a foreign key constraint (`test`.`t2`, CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`b`) REFERENCES `test`.`t1` (`a`))
 SELECT @a, @b;
 @a	@b
 0	0
+DELETE FROM t1;
+SELECT @a, @b;
+@a	@b
+1	1
 INSERT INTO t1 VALUES (1);
 DELETE FROM t1;
 SELECT @a, @b;