MDEV-15492: Subquery crash similar to MDEV-10050

Detection of first execution of PS fixed.
More debug info.

mysql-test/r/ps_qc_innodb.result

+#
+# MDEV-15492: Subquery crash similar to MDEV-10050
+#
+SET @qcs.save= @@global.query_cache_size, @qct.save= @@global.query_cache_type;
+SET GLOBAL query_cache_size= 512*1024*1024, query_cache_type= ON;
+CREATE TABLE t1 (a INT) ENGINE=InnoDB;
+CREATE TABLE t2 (b INT) ENGINE=InnoDB;
+CREATE VIEW v AS select a from t1 join t2;
+PREPARE stmt1 FROM "SELECT * FROM t1 WHERE a in (SELECT a FROM v)";
+PREPARE stmt2 FROM "SELECT * FROM t1 WHERE a in (SELECT a FROM v)";
+EXECUTE stmt2;
+a
+EXECUTE stmt1;
+a
+INSERT INTO t2 VALUES (0);
+EXECUTE stmt1;
+a
+START TRANSACTION;
+EXECUTE stmt1;
+a
+DROP VIEW v;
+DROP TABLE t1, t2;
+SET GLOBAL query_cache_size= @qcs.save, query_cache_type= @qct.save;

mysql-test/t/ps_qc_innodb.test

+--source include/have_query_cache.inc
+--source include/have_innodb.inc
+
+--echo #
+--echo # MDEV-15492: Subquery crash similar to MDEV-10050
+--echo #
+
+SET @qcs.save= @@global.query_cache_size, @qct.save= @@global.query_cache_type;
+SET GLOBAL query_cache_size= 512*1024*1024, query_cache_type= ON;
+
+--connect (con1,localhost,root,,test)
+CREATE TABLE t1 (a INT) ENGINE=InnoDB;
+CREATE TABLE t2 (b INT) ENGINE=InnoDB;
+CREATE VIEW v AS select a from t1 join t2;
+
+PREPARE stmt1 FROM "SELECT * FROM t1 WHERE a in (SELECT a FROM v)";
+
+--connect (con2,localhost,root,,test)
+PREPARE stmt2 FROM "SELECT * FROM t1 WHERE a in (SELECT a FROM v)";
+EXECUTE stmt2;
+
+--connection con1
+EXECUTE stmt1;
+INSERT INTO t2 VALUES (0);
+EXECUTE stmt1;
+START TRANSACTION;
+EXECUTE stmt1;
+
+# Cleanup
+--disconnect con1
+--disconnect con2
+--connection default
+DROP VIEW v;
+DROP TABLE t1, t2;
+SET GLOBAL query_cache_size= @qcs.save, query_cache_type= @qct.save;

sql/sql_class.cc

@@ -2252,15 +2252,19 @@ void THD::check_and_register_item_tree_change(Item **place, Item **new_value,
 
 void THD::rollback_item_tree_changes()
 {
+  DBUG_ENTER("THD::rollback_item_tree_changes");
   I_List_iterator<Item_change_record> it(change_list);
   Item_change_record *change;
 
   while ((change= it++))
   {
+    DBUG_PRINT("info", ("Rollback: %p (%p) <- %p",
+                        *change->place, change->place, change->old_value));
     *change->place= change->old_value;
   }
   /* We can forget about changes memory: it's allocated in runtime memroot */
   change_list.empty();
+  DBUG_VOID_RETURN;
 }
 
 

sql/sql_prepare.cc

@@ -3819,6 +3819,7 @@ bool Prepared_statement::execute(String *expanded_query, bool open_cursor)
   Statement stmt_backup;
   Query_arena *old_stmt_arena;
   bool error= TRUE;
+  bool qc_executed= FALSE;
 
   char saved_cur_db_name_buf[SAFE_NAME_LEN+1];
   LEX_STRING saved_cur_db_name=
@@ -3937,6 +3938,7 @@ bool Prepared_statement::execute(String *expanded_query, bool open_cursor)
       thd->lex->sql_command= SQLCOM_SELECT;
       status_var_increment(thd->status_var.com_stat[SQLCOM_SELECT]);
       thd->update_stats();
+      qc_executed= TRUE;
     }
   }
 
@@ -3960,7 +3962,7 @@ bool Prepared_statement::execute(String *expanded_query, bool open_cursor)
   thd->set_statement(&stmt_backup);
   thd->stmt_arena= old_stmt_arena;
 
-  if (state == Query_arena::STMT_PREPARED)
+  if (state == Query_arena::STMT_PREPARED && !qc_executed)
     state= Query_arena::STMT_EXECUTED;
 
   if (error == 0 && this->lex->sql_command == SQLCOM_CALL)