Bug#54812: assert in Diagnostics_area::set_ok_status

           during EXPLAIN

Before the patch, send_eof() of some subclasses of 
select_result (e.g., select_send::send_eof()) could 
handle being called after an error had occured while others 
could not. The methods that were not well-behaved would trigger
an ASSERT on debug builds. Release builds were not affected.

Consider the following query as an example for how the ASSERT
could be triggered:

A user without execute privilege on f() does
   SELECT MAX(key1) INTO @dummy FROM t1 WHERE f() < 1;
resulting in "ERROR 42000: execute command denied to user..." 

The server would end the query by calling send_eof(). The 
fact that the error had occured would make the ASSERT trigger. 

select_dumpvar::send_eof() was the offending method in the
bug report, but the problem also applied to other 
subclasses of select_result. This patch uniforms send_eof() 
of all subclasses of select_result to handle being called 
after an error has occured. 

1 files changed, 3 insertions, 1 deletions

diff --git a/sql/sql_update.cc b/sql/sql_update.cc
index 96b1ac67b49..8cc8d511fd6 100644
--- a/sql/sql_update.cc
+++ b/sql/sql_update.cc
@@ -2064,7 +2064,9 @@ bool multi_update::send_eof()
      Does updates for the last n - 1 tables, returns 0 if ok;
      error takes into account killed status gained in do_updates()
   */
-  int local_error = (table_count) ? do_updates() : 0;
+  int local_error= thd->is_error();
+  if (!local_error)
+    local_error = (table_count) ? do_updates() : 0;
   /*
     if local_error is not set ON until after do_updates() then
     later carried out killing should not affect binlogging.