Another attempt to fix bug mdev-5103.

The earlier pushed fix for the bug was incomplete. It did not remove
the main cause of the problem: the function remove_eq_conds()
removed always true multiple equalities from any conjunct, but did not
adjust the list of them stored in Item_cond_and::cond_equal.current_level.

Simplified the test case for the bug and moved it to another test file.

The fix triggered changes in EXPLAIN EXTENDED for some queries. 

1 files changed, 6 insertions, 1 deletions

diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index d00f177fc8e..a5d6ec02ace 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -1695,6 +1695,12 @@ class Item_equal: public Item_bool_func
     the equal_items should be ignored.
   */
   bool cond_false;
+  /*
+    This initially is set to FALSE. It becomes TRUE when this item is evaluated
+    as being always true. If the flag is TRUE the contents of the list 
+    the equal_items should be ignored.
+  */
+  bool cond_true;
   /* 
     compare_as_dates=TRUE <-> constants equal to fields from equal_items
     must be compared as datetimes and not as strings.
@@ -1725,7 +1731,6 @@ public:
   Item_equal(Item_equal *item_equal);
   /* Currently the const item is always the first in the list of equal items */
   inline Item* get_const() { return with_const ? equal_items.head() : NULL; }
-  inline bool is_cond_true() { return equal_items.elements == 1; }
   void add_const(Item *c, Item *f = NULL);
   /** Add a non-constant item to the multiple equality */
   void add(Item *f) { equal_items.push_back(f); }