Merge 10.2 into 10.3

1 files changed, 20 insertions, 2 deletions

diff --git a/sql/sql_derived.cc b/sql/sql_derived.cc
index 11d3a13b8b9..eb840e02a27 100644
--- a/sql/sql_derived.cc
+++ b/sql/sql_derived.cc
@@ -1271,7 +1271,8 @@ bool pushdown_cond_for_derived(THD *thd, Item *cond, TABLE_LIST *derived)
     DBUG_RETURN(false);
 
   st_select_lex_unit *unit= derived->get_unit();
-  st_select_lex *sl= unit->first_select();
+  st_select_lex *first_sl= unit->first_select();
+  st_select_lex *sl= first_sl;
 
   if (derived->prohibit_cond_pushdown)
     DBUG_RETURN(false);
@@ -1419,7 +1420,24 @@ bool pushdown_cond_for_derived(THD *thd, Item *cond, TABLE_LIST *derived)
       if (!extracted_cond_copy)
         continue;
     }
-    
+
+    /*
+      Rename the columns of all non-first selects of a union to be compatible
+      by names with the columns of the first select. It will allow to use copies
+      of the same expression pushed into having clauses of different selects.
+    */
+    if (sl != first_sl)
+    {
+      DBUG_ASSERT(sl->item_list.elements == first_sl->item_list.elements);
+      List_iterator_fast<Item> it(sl->item_list);
+      List_iterator_fast<Item> nm_it(unit->types);
+      Item * item;
+      while((item= it++))
+      {
+        item->share_name_with(nm_it++);
+      }
+    }
+
     /*
       Transform the references to the 'derived' columns from the condition
       pushed into the having clause of sl to make them usable in the new context