MDEV-27523 main.delayed fails with wrong error code or timeout when executed after main.deadlock_ftwrl

don't forget to reset mdl_context.m_deadlock_overweight when
taking the THD out of the cache - the history of previous connections
should not affect the weight in deadlock victim selection

(small cleanup of the test to help the correct merge)

mysql-test/main/delayed.result

@@ -1,4 +1,3 @@
-drop table if exists t1;
 create table t1 (a char(10), tmsp timestamp);
 insert into t1 set a = 1;
 insert delayed into t1 set a = 2;
@@ -259,7 +258,6 @@ INSERT DELAYED INTO t1 SET b= b();
 ERROR 42000: FUNCTION test.b does not exist
 DROP TABLE t1;
 End of 5.0 tests
-DROP TABLE IF EXISTS t1,t2;
 SET SQL_MODE='NO_AUTO_VALUE_ON_ZERO';
 CREATE TABLE `t1` (
 `id` int(11) PRIMARY KEY auto_increment,
@@ -293,7 +291,6 @@ set global low_priority_updates = 1;
 select @@global.low_priority_updates;
 @@global.low_priority_updates
 1
-drop table if exists t1;
 create table t1 (a int, b int);
 insert into t1 values (1,1);
 lock table t1 read;
@@ -322,7 +319,6 @@ set global low_priority_updates = @old_delayed_updates;
 #
 # Bug #47682 strange behaviour of INSERT DELAYED
 #
-DROP TABLE IF EXISTS t1, t2;
 CREATE TABLE t1 (f1 integer);
 CREATE TABLE t2 (f1 integer);
 FLUSH TABLES WITH READ LOCK;
@@ -335,8 +331,6 @@ End of 5.1 tests
 #
 # Bug #47274 assert in open_table on CREATE TABLE <already existing>
 #
-DROP TABLE IF EXISTS t1;
-DROP TABLE IF EXISTS t2;
 CREATE TABLE t1 ( f1 INTEGER AUTO_INCREMENT, PRIMARY KEY (f1));
 # The following CREATE TABLEs before gave an assert.
 INSERT DELAYED t1 VALUES (4);
@@ -352,14 +346,12 @@ CREATE TABLE t2 (f1 INTEGER);
 INSERT DELAYED t1 VALUES (7);
 CREATE TABLE t1 LIKE t2;
 ERROR 42S01: Table 't1' already exists
-DROP TABLE t2;
-DROP TABLE t1;
+DROP TABLE t2, t1;
 #
 # Bug#54332 Deadlock with two connections doing LOCK TABLE+INSERT DELAYED
 #
 # This test is not supposed to work under --ps-protocol since
 # INSERT DELAYED doesn't work under LOCK TABLES with this protocol.
-DROP TABLE IF EXISTS t1, t2;
 CREATE TABLE t1 (a INT);
 CREATE TABLE t2 (a INT);
 CREATE TABLE t3 (a INT);
@@ -450,7 +442,6 @@ DROP TABLE t1, t2, t3;
 #
 connect  con1,localhost,root,,;
 connection default;
-drop table if exists t1, t2, tm;
 create table t1(a int);
 create table t2(a int);
 create table tm(a int) engine=merge union=(t1, t2);

mysql-test/main/delayed.test

@@ -21,9 +21,6 @@ select @@global.storage_engine in
 ("memory","myisam","archive","blackhole") as `TRUE`;
 enable_query_log;
 
---disable_warnings
-drop table if exists t1;
---enable_warnings
 create table t1 (a char(10), tmsp timestamp);
 insert into t1 set a = 1;
 insert delayed into t1 set a = 2;
@@ -276,9 +273,6 @@ DROP TABLE t1;
 #
 # Bug#27358 INSERT DELAYED does not honour SQL_MODE of the client
 #
---disable_warnings
-DROP TABLE IF EXISTS t1,t2;
---enable_warnings
 SET SQL_MODE='NO_AUTO_VALUE_ON_ZERO';
 CREATE TABLE `t1` (
   `id` int(11) PRIMARY KEY auto_increment,
@@ -315,9 +309,6 @@ set @old_delayed_updates = @@global.low_priority_updates;
 set global low_priority_updates = 1;
 select @@global.low_priority_updates;
 
---disable_warnings
-drop table if exists t1;
---enable_warnings
 create table t1 (a int, b int);
 insert into t1 values (1,1);
 lock table t1 read;
@@ -351,10 +342,6 @@ set global low_priority_updates = @old_delayed_updates;
 --echo # Bug #47682 strange behaviour of INSERT DELAYED
 --echo #
 
---disable_warnings
-DROP TABLE IF EXISTS t1, t2;
---enable_warnings
-
 CREATE TABLE t1 (f1 integer);
 CREATE TABLE t2 (f1 integer);
 
@@ -378,11 +365,6 @@ DROP TABLE t1, t2;
 --echo # Bug #47274 assert in open_table on CREATE TABLE <already existing>
 --echo #
 
---disable_warnings
-DROP TABLE IF EXISTS t1;
-DROP TABLE IF EXISTS t2;
---enable_warnings
-
 CREATE TABLE t1 ( f1 INTEGER AUTO_INCREMENT, PRIMARY KEY (f1));
 
 --echo # The following CREATE TABLEs before gave an assert.
@@ -404,9 +386,7 @@ INSERT DELAYED t1 VALUES (7);
 --error ER_TABLE_EXISTS_ERROR
 CREATE TABLE t1 LIKE t2;
 
-DROP TABLE t2;
-DROP TABLE t1;
-
+DROP TABLE t2, t1;
 
 --echo #
 --echo # Bug#54332 Deadlock with two connections doing LOCK TABLE+INSERT DELAYED
@@ -417,10 +397,6 @@ DROP TABLE t1;
 --disable_ps_protocol
 --disable_view_protocol
 
---disable_warnings
-DROP TABLE IF EXISTS t1, t2;
---enable_warnings
-
 CREATE TABLE t1 (a INT);
 CREATE TABLE t2 (a INT);
 CREATE TABLE t3 (a INT);
@@ -573,9 +549,6 @@ DROP TABLE t1, t2, t3;
 --disable_view_protocol
 connect (con1,localhost,root,,);
 connection default;
---disable_warnings
-drop table if exists t1, t2, tm;
---enable_warnings
 create table t1(a int);
 create table t2(a int);
 create table tm(a int) engine=merge union=(t1, t2);

sql/mdl.h

@@ -919,7 +919,8 @@ public:
                     already has received some signal or closed
                     signal slot.
   */
-  void init(MDL_context_owner *arg) { m_owner= arg; }
+  void init(MDL_context_owner *arg) { m_owner= arg; reset(); }
+  void reset() { m_deadlock_overweight= 0; }
 
   void set_needs_thr_lock_abort(bool needs_thr_lock_abort)
   {
@@ -1028,7 +1029,7 @@ private:
    */
   MDL_wait_for_subgraph *m_waiting_for;
   LF_PINS *m_pins;
-  uint m_deadlock_overweight= 0;
+  uint m_deadlock_overweight;
 private:
   MDL_ticket *find_ticket(MDL_request *mdl_req,
                           enum_mdl_duration *duration);

sql/sql_class.cc

@@ -1209,6 +1209,7 @@ const Type_handler *THD::type_handler_for_datetime() const
 void THD::init()
 {
   DBUG_ENTER("thd::init");
+  mdl_context.reset();
   mysql_mutex_lock(&LOCK_global_system_variables);
   plugin_thdvar_init(this);
   /*