Bug#11747970 34660: CRASH WHEN FEDERATED TABLE LOSES CONNECTION DURING INSERT ... SELECT

Problematic query:
insert ignore into `t1_federated` (`c1`) select `c1` from  `t1_local` a
where not exists (select 1 from `t1_federated` b where a.c1 = b.c1);
When this query is killed in another connection it could lead to crash.
The problem is follwing:
An attempt to obtain table statistics for subselect table in killed query
fails with an error. So JOIN::optimize() for subquery is failed but
it does not prevent further subquery evaluation.
At the first subquery execution JOIN::optimize() is called
(see subselect_single_select_engine::exec()) and fails with
an error. 'executed' flag is set to TRUE and it prevents
further subquery evaluation. At the second call
JOIN::optimize() does not happen as 'JOIN::optimized' is TRUE
and in case of uncacheable subquery the 'executed' flag is set
to FALSE before subquery evaluation. So we loose 'optimize stage'
error indication (see subselect_single_select_engine::exec()).
In other words 'executed' flag is used for two purposes, for
error indication at JOIN::optimize() stage and for an
indication of subquery execution. And it seems it's wrong
as the flag could be reset.

1 files changed, 10 insertions, 0 deletions

diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 516c9c37473..bf0cd7c9db8 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -2677,6 +2677,16 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables_arg, COND *conds,
     table_vector[i]=s->table=table=tables->table;
     table->pos_in_table_list= tables;
     error= table->file->info(HA_STATUS_VARIABLE | HA_STATUS_NO_LOCK);
+
+    DBUG_EXECUTE_IF("bug11747970_raise_error",
+                    {
+                      if (!error)
+                      {
+                        my_error(ER_UNKNOWN_ERROR, MYF(0));
+                        goto error;
+                      }
+                    });
+
     if (error)
     {
       table->file->print_error(error, MYF(0));