Bug#50624: crash in check_table_access during call procedure

This bug is just one facet of stored routines not being able to
detect changes in meta-data (WL#4179). This particular problem
can be triggered within a single session due to the improper
management of the pre-locking list if the view is expanded after
the pre-locking list is calculated.

Since the overall solution for the meta-data detection issue is
planned for a later release, for now a workaround is used to
fix this particular aspect that only involves a single session.
The workaround is to flush the thread-local stored routine cache
every time a view is created or modified, causing locally cached
routines to be re-evaluated upon invocation.

mysql-test/r/sp-bugs.result

@@ -59,4 +59,18 @@ CALL p1 ();
 ERROR HY000: Trigger does not exist
 DROP TABLE t1;
 DROP PROCEDURE p1;
+#
+# Bug#50423: Crash on second call of a procedure dropping a trigger
+#
+DROP TABLE IF EXISTS t1;
+DROP TRIGGER IF EXISTS tr1;
+DROP PROCEDURE IF EXISTS p1;
+CREATE TABLE t1 (f1 INTEGER);
+CREATE TRIGGER tr1 BEFORE INSERT ON t1 FOR EACH ROW SET @aux = 1;
+CREATE PROCEDURE p1 () DROP TRIGGER tr1;
+CALL p1 ();
+CALL p1 ();
+ERROR HY000: Trigger does not exist
+DROP TABLE t1;
+DROP PROCEDURE p1;
 End of 5.1 tests

mysql-test/t/sp-bugs.test

@@ -80,4 +80,25 @@ CALL p1 ();
 DROP TABLE t1;
 DROP PROCEDURE p1;
 
+--echo #
+--echo # Bug#50423: Crash on second call of a procedure dropping a trigger
+--echo #
+
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+DROP TRIGGER IF EXISTS tr1;
+DROP PROCEDURE IF EXISTS p1;
+--enable_warnings
+
+CREATE TABLE t1 (f1 INTEGER);
+CREATE TRIGGER tr1 BEFORE INSERT ON t1 FOR EACH ROW SET @aux = 1;
+CREATE PROCEDURE p1 () DROP TRIGGER tr1;
+
+CALL p1 ();
+--error ER_TRG_DOES_NOT_EXIST
+CALL p1 ();
+
+DROP TABLE t1;
+DROP PROCEDURE p1;
+
 --echo End of 5.1 tests

sql/sp_cache.cc

@@ -175,8 +175,9 @@ sp_head *sp_cache_lookup(sp_cache **cp, sp_name *name)
     sp_cache_invalidate()
       
   NOTE
-    This is called when a VIEW definition is modifed. We can't destroy sp_head
-    objects here as one may modify VIEW definitions from prelocking-free SPs.
+    This is called when a VIEW definition is created or modified (and in some
+    other contexts). We can't destroy sp_head objects here as one may modify
+    VIEW definitions from prelocking-free SPs.
 */
 
 void sp_cache_invalidate()

sql/sql_view.cc

@@ -400,17 +400,14 @@ bool mysql_create_view(THD *thd, TABLE_LIST *views,
   DBUG_ASSERT(!lex->proc_list.first && !lex->result &&
               !lex->param_list.elements);
 
-  if (mode != VIEW_CREATE_NEW)
+  if (mode == VIEW_ALTER && fill_defined_view_parts(thd, view))
   {
-    if (mode == VIEW_ALTER &&
-        fill_defined_view_parts(thd, view))
-    {
-      res= TRUE;
-      goto err;
-    }
-    sp_cache_invalidate();
+    res= TRUE;
+    goto err;
   }
 
+  sp_cache_invalidate();
+
   if (!lex->definer)
   {
     /*