Merge of fix for bug#58553, "Queries with pushed conditions causes 'explain

extended' to crash mysqld" (see http://lists.mysql.com/commits/128409).

sql/handler.cc

@@ -4759,6 +4759,7 @@ int handler::ha_reset()
   free_io_cache(table);
   /* reset the bitmaps to point to defaults */
   table->default_column_bitmaps();
+  pushed_cond= NULL;
   DBUG_RETURN(reset());
 }
 

sql/sql_base.cc

@@ -3068,6 +3068,11 @@ bool open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
   table->reginfo.lock_type=TL_READ;		/* Assume read */
 
  reset:
+  /*
+    Check that there is no reference to a condtion from an earlier query
+    (cf. Bug#58553). 
+  */
+  DBUG_ASSERT(table->file->pushed_cond == NULL);
   table_list->updatable= 1; // It is not derived table nor non-updatable VIEW
   table_list->table= table;
 

sql/sql_select.cc

@@ -6476,7 +6476,6 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
           tab->select_cond=sel->cond=tmp;
           /* Push condition to storage engine if this is enabled
              and the condition is not guarded */
-          tab->table->file->pushed_cond= NULL;
 	  if (thd->variables.optimizer_switch &
               OPTIMIZER_SWITCH_ENGINE_CONDITION_PUSHDOWN)
           {