BUG#912513: Wrong result (missing rows) with join_cache_hashed+materialization+semijoin=on

- equality substitution code was geared towards processing WHERE/ON clauses.
  that is, it assumed that it was doing substitions on the code that 
   = wasn't attached to any particular join_tab yet
   = was going to be fed to make_join_select() which would take the condition
     apart and attach various parts of it to tables inside/outside semi-joins.
- However, somebody added equality substition for ref access. That is, if 
  we have a ref access on TBL.key=expr, they would do equality substition in
  'expr'. This possibility wasn't accounted for.
- Fixed equality substition code by adding a mode that does equality 
  substition under assumption that the processed expression will be 
  attached to a certain particular table TBL.

1 files changed, 4 insertions, 2 deletions

diff --git a/sql/item.cc b/sql/item.cc
index d0608e392b3..aaf9b0c2a12 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -5023,7 +5023,8 @@ bool Item_field::set_no_const_sub(uchar *arg)
 
 Item *Item_field::replace_equal_field(uchar *arg)
 {
-  if (item_equal && item_equal == (Item_equal *) arg)
+  REPLACE_EQUAL_FIELD_ARG* param= (REPLACE_EQUAL_FIELD_ARG*)arg;
+  if (item_equal && item_equal == param->item_equal)
   {
     Item *const_item= item_equal->get_const();
     if (const_item)
@@ -5033,7 +5034,8 @@ Item *Item_field::replace_equal_field(uchar *arg)
         return this;
       return const_item;
     }
-    Item_field *subst= (Item_field *)(item_equal->get_first(this));
+    Item_field *subst= 
+      (Item_field *)(item_equal->get_first(param->context_tab, this));
     if (subst)
       subst= (Item_field *) (subst->real_item());
     if (subst && !field->eq(subst->field))