A fix and a test case for Bug#19399 "res 'Lost Connection' when

dropping/creating tables".

The bug could lead to a crash when multi-delete statements were
prepared and used with temporary tables.

The bug was caused by lack of clean-up of multi-delete tables before
re-execution of a prepared statement. In a statement like
DELETE t1 FROM t1, t2 WHERE ... the first table list (t1) is
moved to lex->auxilliary_table_list and excluded from lex->query_tables
or select_lex->tables. Thus it was unaccessible to reinit_stmt_before_use
and not cleaned up before re-execution of a prepared statement. 

1 files changed, 13 insertions, 7 deletions

diff --git a/sql/sql_prepare.cc b/sql/sql_prepare.cc
index 2d9e80df63c..2688841d96c 100644
--- a/sql/sql_prepare.cc
+++ b/sql/sql_prepare.cc
@@ -1727,14 +1727,9 @@ static void reset_stmt_for_execute(Prepared_statement *stmt)
 	 tables;
 	 tables= tables->next)
     {
-      /*
-        Reset old pointers to TABLEs: they are not valid since the tables
-        were closed in the end of previous prepare or execute call.
-      */
-      tables->table= 0;
-      tables->table_list= 0;
+      tables->reinit_before_use(thd);
     }
-    
+
     {
       SELECT_LEX_UNIT *unit= sl->master_unit();
       unit->unclean();
@@ -1743,6 +1738,17 @@ static void reset_stmt_for_execute(Prepared_statement *stmt)
       unit->reinit_exec_mechanism();
     }
   }
+  /*
+    Cleanup of the special case of DELETE t1, t2 FROM t1, t2, t3 ...
+    (multi-delete).  We do a full clean up, although at the moment all we
+    need to clean in the tables of MULTI-DELETE list is 'table' member.
+  */
+  for (TABLE_LIST *tables= (TABLE_LIST*) lex->auxilliary_table_list.first;
+       tables;
+       tables= tables->next)
+  {
+    tables->reinit_before_use(thd);
+  }
   lex->current_select= &lex->select_lex;
   if (lex->result)
     lex->result->cleanup();