MDEV-26048 Table 'test._test_new' doesn't exist when add trigger (use pt-osc)

There is inconsistency happens between two INSERTs. First INSERT
happens after only tr1 was created. It enters
DML_prelocking_strategy::handle_table() and sets need_prelocking as
there is table->triggers. But there is no relevant triggers: tr1 is
TRG_EVENT_DELETE, so nothing was added for prelocking. Nonetheless,
extend_table_list() calls mark_as_requiring_prelocking() based on
need_prelocking. It sets lex->query_tables_own_last to
save_query_tables_last which is double pointer to NULL. Then
reset_lex_and_exec_core() based on that value (double pointer is
non-NULL itself) propagates that to SP's m_lex.

After tr2 created, next execution of INSERT thinks it has prelocking
list. extend_table_list() receives has_prelocking_list:true and
skips handle_table() (and therefore any prelocking list updates).

As a result when process_triggers() is trying to open t2 it does not
see it in the list of open (and prelocked) tables and fails with
ER_NO_SUCH_TABLE (which is misleading error code as t2 exists).

The fix avoids setting need_prelocking for the cases when no triggers
executed (i.e. no matching event type).

Note that we can not disable prelocking for triggers without any
tables like that:

  *need_prelocking|= trigger->add_used_tables_to_table_list(thd,
	     &prelocking_ctx->query_tables_last,
	     table_list->belong_to_view);

because trigger must be executed under LTM_PRELOCKED, otherwise it
will close not own tables (this can be further improved, see TODO in
the patch).

Thanks to Chǔ Huáxīng <15381158111@163.com> for the patch idea.

mysql-test/main/sp_sync.result

@@ -117,3 +117,35 @@ ERROR 42000: Unknown database 's1'
 connection default;
 disconnect con3;
 SET DEBUG_SYNC = 'RESET';
+#
+# MDEV-26048 Table 'test._test_new' doesn't exist when add trigger (use pt-osc)
+#
+create table t1 (x int);
+create procedure sp()
+begin
+declare a int default 1;
+while a <= 2 do
+set debug_sync= concat("now wait_for created_", a);
+insert into t1 values(a);
+set debug_sync= "now signal inserted";
+set a= a + 1;
+end while;
+end$$
+connect  con1,localhost,root,,test;
+call sp();
+connection default;
+create table t2 (y int);
+create trigger tr1 after delete on t1 for each row delete from t2;
+set debug_sync= "now signal created_1";
+set debug_sync= "now wait_for inserted";
+create trigger tr2 after insert on t1 for each row insert t2 values (0);
+set debug_sync= "now signal created_2";
+connection con1;
+disconnect con1;
+connection default;
+drop trigger tr1;
+drop trigger tr2;
+drop table t2;
+drop procedure sp;
+drop table t1;
+set debug_sync= "reset";

mysql-test/main/sp_sync.test

@@ -168,3 +168,49 @@ SET DEBUG_SYNC = 'RESET';
 # Check that all connections opened by test cases in this file are really
 # gone so execution of other tests won't be affected by their presence.
 --source include/wait_until_count_sessions.inc
+
+--echo #
+--echo # MDEV-26048 Table 'test._test_new' doesn't exist when add trigger (use pt-osc)
+--echo #
+create table t1 (x int);
+
+--delimiter $$
+# Note: it's important to do INSERT in a loop as
+# the bug reproduces only on the same statetement
+# (has_prelocking_list depends on it)
+create procedure sp()
+begin
+  declare a int default 1;
+  while a <= 2 do
+    set debug_sync= concat("now wait_for created_", a);
+    insert into t1 values(a);
+    set debug_sync= "now signal inserted";
+    set a= a + 1;
+  end while;
+end$$
+--delimiter ;
+
+--connect (con1,localhost,root,,test)
+send call sp();
+--connection default
+
+create table t2 (y int);
+create trigger tr1 after delete on t1 for each row delete from t2;
+set debug_sync= "now signal created_1";
+set debug_sync= "now wait_for inserted";
+create trigger tr2 after insert on t1 for each row insert t2 values (0);
+set debug_sync= "now signal created_2";
+
+--connection con1
+--reap
+
+--disconnect con1
+--connection default
+drop trigger tr1;
+drop trigger tr2;
+drop table t2;
+drop procedure sp;
+drop table t1;
+set debug_sync= "reset";
+
+# End of 10.11 tests

sql/sp_head.cc

@@ -3572,6 +3572,8 @@ sp_lex_keeper::reset_lex_and_exec_core(THD *thd, uint *nextp,
         We've already entered/left prelocked mode with this statement.
         Attach the list of tables that need to be prelocked and mark m_lex
         as having such list attached.
+
+        TODO: DBUG_ASSERT(prelocking_tables);
       */
       *lex_query_tables_own_last= prelocking_tables;
       m_lex->mark_as_requiring_prelocking(lex_query_tables_own_last);

sql/sp_head.h

@@ -1269,7 +1269,8 @@ class sp_lex_keeper
 public:
 
   sp_lex_keeper(LEX *lex, bool lex_resp)
-    : m_lex(lex), m_lex_resp(lex_resp), 
+    : m_lex(lex), m_lex_resp(lex_resp),
+      prelocking_tables(NULL),
       lex_query_tables_own_last(NULL)
   {
     lex->sp_lex_in_use= TRUE;

sql/sql_base.cc

@@ -3709,7 +3709,12 @@ bool extend_table_list(THD *thd, TABLE_LIST *tables,
                                              &need_prelocking);
 
     if (need_prelocking && ! lex->requires_prelocking())
+    {
+      /*
+        TODO: DBUG_ASSERT(save_query_tables_last != lex->query_tables_last);
+      */
       lex->mark_as_requiring_prelocking(save_query_tables_last);
+    }
   }
   return error;
 }
@@ -4912,14 +4917,10 @@ bool DML_prelocking_strategy::handle_table(THD *thd,
 
   if (table_list->trg_event_map)
   {
-    if (table->triggers)
-    {
-      *need_prelocking= TRUE;
-
-      if (table->triggers->
-          add_tables_and_routines_for_triggers(thd, prelocking_ctx, table_list))
-        return TRUE;
-    }
+    Table_triggers_list *tr= table->triggers;
+    if (tr && tr->add_tables_and_routines_for_triggers(thd, prelocking_ctx,
+                                                       table_list, need_prelocking))
+      return true;
 
     if (prepare_fk_prelocking_list(thd, prelocking_ctx, table_list,
                                    need_prelocking,

sql/sql_trigger.cc

@@ -2532,7 +2532,8 @@ bool
 Table_triggers_list::
 add_tables_and_routines_for_triggers(THD *thd,
                                      Query_tables_list *prelocking_ctx,
-                                     TABLE_LIST *table_list)
+                                     TABLE_LIST *table_list,
+                                     bool *need_prelocking)
 {
   DBUG_ASSERT(static_cast<int>(table_list->lock_type) >=
               static_cast<int>(TL_FIRST_WRITE));
@@ -2552,6 +2553,8 @@ add_tables_and_routines_for_triggers(THD *thd,
           if (unlikely(!triggers->body))                  // Parse error
             continue;
 
+          *need_prelocking= true;
+
           MDL_key key(MDL_key::TRIGGER, trigger->m_db.str, trigger->m_name.str);
 
           if (sp_add_used_routine(prelocking_ctx,

sql/sql_trigger.h

@@ -309,7 +309,8 @@ public:
 
   bool add_tables_and_routines_for_triggers(THD *thd,
                                             Query_tables_list *prelocking_ctx,
-                                            TABLE_LIST *table_list);
+                                            TABLE_LIST *table_list,
+                                            bool *need_prelocking);
 
   Field **nullable_fields() { return record0_field; }
   void clear_extra_null_bitmap()