Fixed bug mdev-4355.

This patch almost totally revised the patch for bug mdev-4177.
The latter had too many defects. In particular, it did not
propagate multiple equalities formed when merging a degenerate
disjunct into underlying AND formula.

8 files changed, 507 insertions, 104 deletions

diff --git a/mysql-test/r/select.result b/mysql-test/r/select.result
index 953b1409827..dfc5236f794 100644
--- a/mysql-test/r/select.result
+++ b/mysql-test/r/select.result
@@ -5155,7 +5155,7 @@ a	b	c
 8	8	8
 DROP TABLE t1,t2;
 #
-# Bug mdev-4413: another manifestations of bug mdev-2474
+# Bug mdev-4413: another manifestations of bug mdev-4274
 #                (valgrind complains)
 #
 CREATE TABLE t1 (a int, b int) ENGINE=MyISAM;
@@ -5167,4 +5167,54 @@ WHERE c = a AND
 ( 0 OR ( b BETWEEN 45 AND 300 OR a > 45 AND a < 100 ) AND b = c );
 a	b	c
 DROP TABLE t1, t2;
+#
+# Bug mdev-4355: equalities from the result of simplification of OR
+#                are not propagated to lower AND levels
+#
+CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (1,101),(2,102),(3,103),(4,104),(5,11);
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (1 != 1 OR a = 5) AND (b != 1 OR a = 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`a` = 5) and (`test`.`t1`.`b` <> 1))
+SELECT * FROM t1 WHERE (1 != 1 OR a = 5) AND (b != 1 OR a = 1);
+a	b
+5	11
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (1 != 1 OR a = 5);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`a` = 5) and (`test`.`t1`.`b` <> 1))
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (1 != 1 OR a = 5);
+a	b
+5	11
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (a = 5 OR 1 != 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`a` = 5) and (`test`.`t1`.`b` <> 1))
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (a = 5 OR 1 != 1);
+a	b
+5	11
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b = 1 OR a = 1) AND (b = 5 AND a = 5 OR 1 != 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where 0
+SELECT * FROM t1 WHERE (b = 1 OR a = 1) AND (b = 5 AND a = 5 OR 1 != 1);
+a	b
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b = 1 OR a = 5) AND (b = 5 AND a = 5 OR 1 != 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`b` = 5) and (`test`.`t1`.`a` = 5))
+SELECT * FROM t1 WHERE (b = 1 OR a = 5) AND (b = 5 AND a = 5 OR 1 != 1);
+a	b
+DROP TABLE t1;
 End of 5.3 tests
diff --git a/mysql-test/r/select_jcl6.result b/mysql-test/r/select_jcl6.result
index d2faa9e85e1..6eb0d65a72f 100644
--- a/mysql-test/r/select_jcl6.result
+++ b/mysql-test/r/select_jcl6.result
@@ -5166,7 +5166,7 @@ a	b	c
 8	8	8
 DROP TABLE t1,t2;
 #
-# Bug mdev-4413: another manifestations of bug mdev-2474
+# Bug mdev-4413: another manifestations of bug mdev-4274
 #                (valgrind complains)
 #
 CREATE TABLE t1 (a int, b int) ENGINE=MyISAM;
@@ -5178,6 +5178,56 @@ WHERE c = a AND
 ( 0 OR ( b BETWEEN 45 AND 300 OR a > 45 AND a < 100 ) AND b = c );
 a	b	c
 DROP TABLE t1, t2;
+#
+# Bug mdev-4355: equalities from the result of simplification of OR
+#                are not propagated to lower AND levels
+#
+CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (1,101),(2,102),(3,103),(4,104),(5,11);
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (1 != 1 OR a = 5) AND (b != 1 OR a = 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`a` = 5) and (`test`.`t1`.`b` <> 1))
+SELECT * FROM t1 WHERE (1 != 1 OR a = 5) AND (b != 1 OR a = 1);
+a	b
+5	11
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (1 != 1 OR a = 5);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`a` = 5) and (`test`.`t1`.`b` <> 1))
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (1 != 1 OR a = 5);
+a	b
+5	11
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (a = 5 OR 1 != 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`a` = 5) and (`test`.`t1`.`b` <> 1))
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (a = 5 OR 1 != 1);
+a	b
+5	11
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b = 1 OR a = 1) AND (b = 5 AND a = 5 OR 1 != 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where 0
+SELECT * FROM t1 WHERE (b = 1 OR a = 1) AND (b = 5 AND a = 5 OR 1 != 1);
+a	b
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b = 1 OR a = 5) AND (b = 5 AND a = 5 OR 1 != 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`b` = 5) and (`test`.`t1`.`a` = 5))
+SELECT * FROM t1 WHERE (b = 1 OR a = 5) AND (b = 5 AND a = 5 OR 1 != 1);
+a	b
+DROP TABLE t1;
 End of 5.3 tests
 set join_cache_level=default;
 show variables like 'join_cache_level';
diff --git a/mysql-test/r/select_pkeycache.result b/mysql-test/r/select_pkeycache.result
index 953b1409827..dfc5236f794 100644
--- a/mysql-test/r/select_pkeycache.result
+++ b/mysql-test/r/select_pkeycache.result
@@ -5155,7 +5155,7 @@ a	b	c
 8	8	8
 DROP TABLE t1,t2;
 #
-# Bug mdev-4413: another manifestations of bug mdev-2474
+# Bug mdev-4413: another manifestations of bug mdev-4274
 #                (valgrind complains)
 #
 CREATE TABLE t1 (a int, b int) ENGINE=MyISAM;
@@ -5167,4 +5167,54 @@ WHERE c = a AND
 ( 0 OR ( b BETWEEN 45 AND 300 OR a > 45 AND a < 100 ) AND b = c );
 a	b	c
 DROP TABLE t1, t2;
+#
+# Bug mdev-4355: equalities from the result of simplification of OR
+#                are not propagated to lower AND levels
+#
+CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (1,101),(2,102),(3,103),(4,104),(5,11);
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (1 != 1 OR a = 5) AND (b != 1 OR a = 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`a` = 5) and (`test`.`t1`.`b` <> 1))
+SELECT * FROM t1 WHERE (1 != 1 OR a = 5) AND (b != 1 OR a = 1);
+a	b
+5	11
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (1 != 1 OR a = 5);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`a` = 5) and (`test`.`t1`.`b` <> 1))
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (1 != 1 OR a = 5);
+a	b
+5	11
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (a = 5 OR 1 != 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`a` = 5) and (`test`.`t1`.`b` <> 1))
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (a = 5 OR 1 != 1);
+a	b
+5	11
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b = 1 OR a = 1) AND (b = 5 AND a = 5 OR 1 != 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where 0
+SELECT * FROM t1 WHERE (b = 1 OR a = 1) AND (b = 5 AND a = 5 OR 1 != 1);
+a	b
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b = 1 OR a = 5) AND (b = 5 AND a = 5 OR 1 != 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`b` = 5) and (`test`.`t1`.`a` = 5))
+SELECT * FROM t1 WHERE (b = 1 OR a = 5) AND (b = 5 AND a = 5 OR 1 != 1);
+a	b
+DROP TABLE t1;
 End of 5.3 tests
diff --git a/mysql-test/r/subselect_sj2_mat.result b/mysql-test/r/subselect_sj2_mat.result
index 18e3f6ddd34..bf5b95d2d8f 100644
--- a/mysql-test/r/subselect_sj2_mat.result
+++ b/mysql-test/r/subselect_sj2_mat.result
@@ -1380,7 +1380,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 2	MATERIALIZED	t3	hash_ALL	NULL	#hash#$hj	5	test.t2.i2	3	100.00	Using where; Using join buffer (flat, BNLH join)
 Warnings:
-Note	1003	select `test`.`t1`.`i1` AS `i1` from `test`.`t1` semi join (`test`.`t2` join `test`.`t3`) where ((`test`.`t3`.`i3` = `test`.`t2`.`i2`) and (`test`.`t1`.`i1` = `test`.`t2`.`i2`) and (`test`.`t2`.`i2` > 0))
+Note	1003	select `test`.`t1`.`i1` AS `i1` from `test`.`t1` semi join (`test`.`t2` join `test`.`t3`) where ((`test`.`t3`.`i3` = `test`.`t2`.`i2`) and (`test`.`t1`.`i1` = `test`.`t2`.`i2`) and (`test`.`t3`.`i3` > 0))
 SELECT * FROM t1 
 WHERE i1 IN (SELECT i3 FROM t2, t3 WHERE i3 > 0 AND i3 = i2 OR 1=2);
 i1
diff --git a/mysql-test/t/select.test b/mysql-test/t/select.test
index 54168332664..94e169821e9 100644
--- a/mysql-test/t/select.test
+++ b/mysql-test/t/select.test
@@ -4326,7 +4326,7 @@ SELECT * FROM t1 INNER JOIN t2 ON ( c = a )
 DROP TABLE t1,t2;
 
 --echo #
---echo # Bug mdev-4413: another manifestations of bug mdev-2474
+--echo # Bug mdev-4413: another manifestations of bug mdev-4274
 --echo #                (valgrind complains)
 --echo #
 
@@ -4342,4 +4342,34 @@ SELECT * FROM t1, t2
 
 DROP TABLE t1, t2;
 
+--echo #
+--echo # Bug mdev-4355: equalities from the result of simplification of OR
+--echo #                are not propagated to lower AND levels
+--echo #
+
+CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (1,101),(2,102),(3,103),(4,104),(5,11);
+
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (1 != 1 OR a = 5) AND (b != 1 OR a = 1);
+SELECT * FROM t1 WHERE (1 != 1 OR a = 5) AND (b != 1 OR a = 1);
+
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (1 != 1 OR a = 5);
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (1 != 1 OR a = 5);
+
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (a = 5 OR 1 != 1);
+SELECT * FROM t1 WHERE (b != 1 OR a = 1) AND (a = 5 OR 1 != 1);
+
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b = 1 OR a = 1) AND (b = 5 AND a = 5 OR 1 != 1);
+SELECT * FROM t1 WHERE (b = 1 OR a = 1) AND (b = 5 AND a = 5 OR 1 != 1);
+
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE (b = 1 OR a = 5) AND (b = 5 AND a = 5 OR 1 != 1);
+SELECT * FROM t1 WHERE (b = 1 OR a = 5) AND (b = 5 AND a = 5 OR 1 != 1);
+
+DROP TABLE t1;
+
 --echo End of 5.3 tests
diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index b2a91c8ec1e..5614533fc8a 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -5608,10 +5608,12 @@ void Item_equal::merge(Item_equal *item)
   @brief
   Merge members of another Item_equal object into this one
   
-  @param item    multiple equality whose members are to be merged
+  @param item         multiple equality whose members are to be merged
+  @param save_merged  keep the list of equalities in 'item' intact
+                      (e.g. for other merges)
 
   @details
-  If the Item_equal 'item' happened to have some elements of the list
+  If the Item_equal 'item' happens to have some elements of the list
   of equal items belonging to 'this' object then the function merges
   the equal items from 'item' into this list.
   If both lists contains constants and they are different then
@@ -5626,24 +5628,45 @@ void Item_equal::merge(Item_equal *item)
   The method 'merge' just joins the list of equal items belonging to 'item'
   to the list of equal items belonging to this object assuming that the lists
   are disjoint. It would be more correct to call the method 'join'.
-  The method 'merge_with_check' really merges two lists of equal items if they
-  have common members.  
+  The method 'merge_into_with_check' really merges two lists of equal items if
+  they have common members.  
 */
   
-bool Item_equal::merge_with_check(Item_equal *item)
+bool Item_equal::merge_with_check(Item_equal *item, bool save_merged)
 {
   bool intersected= FALSE;
-  Item_equal_fields_iterator_slow fi(*this);
+  Item_equal_fields_iterator_slow fi(*item);
+  
   while (fi++)
   {
-    if (item->contains(fi.get_curr_field()))
+    if (contains(fi.get_curr_field()))
     {
-      fi.remove();
       intersected= TRUE;
+      if (!save_merged)
+        fi.remove();
     }
   }
   if (intersected)
-    item->merge(this);
+  {
+    if (!save_merged)
+      merge(item);
+    else
+    {
+      Item *c= item->get_const();
+      if (c)
+        add_const(c);
+      if (!cond_false)
+      {
+        Item *item;
+        fi.rewind();
+        while ((item= fi++))
+	{
+          if (!contains(fi.get_curr_field()))
+            add(item);
+        }
+      }
+    }         
+  }
   return intersected;
 }
 
@@ -5652,17 +5675,25 @@ bool Item_equal::merge_with_check(Item_equal *item)
   @brief
   Merge this object into a list of Item_equal objects 
   
-  @param list   the list of Item_equal objects to merge into
+  @param list                 the list of Item_equal objects to merge into
+  @param save_merged          keep the list of equalities in 'this' intact
+                              (e.g. for other merges)
+  @param only_intersected     do not merge if there are no common members
+                              in any of Item_equal objects from the list
+                              and this Item_equal
 
   @details
   If the list of equal items from 'this' object contains common members
   with the lists of equal items belonging to Item_equal objects from 'list'
   then all involved Item_equal objects e1,...,ek are merged into one 
-  Item equal that replaces e1,...,ek in the 'list'. Otherwise this
+  Item equal that replaces e1,...,ek in the 'list'. Otherwise, in the case
+  when the value of the parameter only_if_intersected is false, this
   Item_equal is joined to the 'list'.
 */
 
-void Item_equal::merge_into_list(List<Item_equal> *list)
+void Item_equal::merge_into_list(List<Item_equal> *list,
+                                 bool save_merged,
+                                 bool only_intersected)
 {
   Item_equal *item;
   List_iterator<Item_equal> it(*list);
@@ -5671,16 +5702,16 @@ void Item_equal::merge_into_list(List<Item_equal> *list)
   {
     if (!merge_into)
     {
-      if (merge_with_check(item))
+      if (item->merge_with_check(this, save_merged))
         merge_into= item;
     }
     else
     {
-      if (item->merge_with_check(merge_into))
+      if (merge_into->merge_with_check(item, false))
         it.remove();
     }
   }
-  if (!merge_into)
+  if (!only_intersected && !merge_into)
     list->push_back(this);
 }
 
diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index 1b8687cfcfc..0ed16c86c0a 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -1761,8 +1761,9 @@ public:
   /** Get number of field items / references to field items in this object */   
   uint n_field_items() { return equal_items.elements-test(with_const); }
   void merge(Item_equal *item);
-  bool merge_with_check(Item_equal *equal_item);
-  void merge_into_list(List<Item_equal> *list);
+  bool merge_with_check(Item_equal *equal_item, bool save_merged);
+  void merge_into_list(List<Item_equal> *list, bool save_merged,
+                      bool only_intersected);
   void update_const();
   enum Functype functype() const { return MULT_EQUAL_FUNC; }
   longlong val_int(); 
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 40021baa954..bc1756ce171 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -13134,14 +13134,175 @@ optimize_cond(JOIN *join, COND *conds,
 
 
 /**
-  Remove const and eq items.
+  @brief
+  Propagate multiple equalities to the sub-expressions of a condition
+
+  @param thd             thread handle
+  @param cond            the condition where equalities are to be propagated
+  @param *new_equalities the multiple equalities to be propagated
+  @param inherited        path to all inherited multiple equality items
+  @param[out] is_simplifiable_cond   'cond' may be simplified after the
+                                      propagation of the equalities
+ 
+  @details
+  The function recursively traverses the tree of the condition 'cond' and
+  for each its AND sub-level of any depth the function merges the multiple
+  equalities from the list 'new_equalities' into the multiple equalities
+  attached to the AND item created for this sub-level.
+  The function also [re]sets references to the equalities formed by the
+  merges of multiple equalities in all field items occurred in 'cond'
+  that are encountered in the equalities.
+  If the result of any merge of multiple equalities is an impossible
+  condition the function returns TRUE in the parameter is_simplifiable_cond.   
+*/
+
+void propagate_new_equalities(THD *thd, Item *cond,
+                              List<Item_equal> *new_equalities,
+                              COND_EQUAL *inherited,
+                              bool *is_simplifiable_cond)
+{
+  if (cond->type() == Item::COND_ITEM)
+  {
+    bool and_level= ((Item_cond*) cond)->functype() == Item_func::COND_AND_FUNC;
+    if (and_level)
+    {
+      Item_cond_and *cond_and= (Item_cond_and *) cond; 
+      List<Item_equal> *cond_equalities= &cond_and->cond_equal.current_level;
+      inherited= cond_and->cond_equal.upper_levels;
+      if (!cond_equalities->is_empty() && cond_equalities != new_equalities)
+      {
+        Item_equal *equal_item;
+        List_iterator<Item_equal> it(*new_equalities);
+	while ((equal_item= it++))
+	{
+          equal_item->merge_into_list(cond_equalities, true, true);
+        }
+        List_iterator<Item_equal> ei(*cond_equalities);
+        while ((equal_item= ei++))
+	{
+          if (equal_item->const_item() && !equal_item->val_int())
+	  {
+            *is_simplifiable_cond= true;
+            return;
+          }
+        }
+      }
+    }
 
+    Item *item;
+    List_iterator<Item> li(*((Item_cond*) cond)->argument_list());
+    while ((item= li++))
+    {
+      propagate_new_equalities(thd, item, new_equalities, inherited,
+                               is_simplifiable_cond);
+    }
+  }
+  else if (cond->type() == Item::FUNC_ITEM && 
+           ((Item_cond*) cond)->functype() == Item_func::MULT_EQUAL_FUNC)
+  {
+    Item_equal *equal_item;
+    List_iterator<Item_equal> it(*new_equalities);
+    Item_equal *equality= (Item_equal *) cond;
+    while ((equal_item= it++))
+    {
+      equality->merge_with_check(equal_item, true);
+    }
+    if (equality->const_item() && !equality->val_int())
+      *is_simplifiable_cond= true;
+  }
+  else
+  {
+    uchar* is_subst_valid= (uchar *) Item::ANY_SUBST;
+    cond= cond->compile(&Item::subst_argument_checker,
+                        &is_subst_valid, 
+                        &Item::equal_fields_propagator,
+                        (uchar *) inherited);
+    cond->update_used_tables();
+  }          
+} 
+
+
+
+/**
+  @brief
+  Evaluate all constant boolean sub-expressions in a condition
+ 
+  @param thd        thread handle
+  @param cond       condition where where to evaluate constant sub-expressions
+  @param[out] cond_value : the returned value of the condition 
+                           (TRUE/FALSE/UNKNOWN:
+                           Item::COND_TRUE/Item::COND_FALSE/Item::COND_OK)
   @return
-    Return new item, or NULL if no condition @n
-    cond_value is set to according:
-    - COND_OK     : query is possible (field = constant)
-    - COND_TRUE   : always true	( 1 = 1 )
-    - COND_FALSE  : always false	( 1 = 2 )
+   the item that is the result of the substitution of all inexpensive constant
+   boolean sub-expressions into cond, or,
+   NULL if the condition is constant and is evaluated to FALSE.
+
+  @details
+  This function looks for all inexpensive constant boolean sub-expressions in
+  the given condition 'cond' and substitutes them for their values.
+  For example, the condition 2 > (5 + 1) or a < (10 / 2)
+  will be transformed to the condition a < (10 / 2).
+  Note that a constant sub-expression is evaluated only if it is constant and
+  inexpensive. A sub-expression with an uncorrelated subquery may be evaluated
+  only if the subquery is considered as inexpensive.
+  The function does not evaluate a constant sub-expression if it is not on one
+  of AND/OR levels of the condition 'cond'. For example, the subquery in the
+  condition a > (select max(b) from t1 where b > 5) will never be evaluated
+  by this function. 
+  If a constant boolean sub-expression is evaluated to TRUE then:
+    - when the sub-expression is a conjunct of an AND formula it is simply
+      removed from this formula
+    - when the sub-expression is a disjunct of an OR formula the whole OR
+      formula is converted to TRUE 
+  If a constant boolean sub-expression is evaluated to FALSE then:
+    - when the sub-expression is a disjunct of an OR formula it is simply
+      removed from this formula
+    - when the sub-expression is a conjuct of an AND formula the whole AND
+      formula is converted to FALSE
+  When a disjunct/conjunct is removed from an OR/AND formula it might happen
+  that there is only one conjunct/disjunct remaining. In this case this
+  remaining disjunct/conjunct must be merged into underlying AND/OR formula,
+  because AND/OR levels must alternate in the same way as they alternate
+  after fix_fields() is called for the original condition.
+  The specifics of merging a formula f into an AND formula A appears
+  when A contains multiple equalities and f contains multiple equalities.
+  In this case the multiple equalities from f and A have to be merged.
+  After this the resulting multiple equalities have to be propagated into
+  the all AND/OR levels of the formula A (see propagate_new_equalities()).
+  The propagation of multiple equalities might result in forming multiple
+  equalities that are always FALSE. This, in its turn, might trigger further
+  simplification of the condition.
+
+  @note
+  EXAMPLE 1:
+  SELECT * FROM t1 WHERE (b = 1 OR a = 1) AND (b = 5 AND a = 5 OR 1 != 1);
+  First 1 != 1 will be removed from the second conjunct:
+  => SELECT * FROM t1 WHERE (b = 1 OR a = 1) AND (b = 5 AND a = 5);
+  Then (b = 5 AND a = 5) will be merged into the top level condition:
+  => SELECT * FROM t1 WHERE (b = 1 OR a = 1) AND (b = 5) AND (a = 5);
+  Then (b = 5), (a = 5)  will be propagated into the disjuncs of 
+  (b = 1 OR a = 1):
+  => SELECT * FROM t1 WHERE ((b = 1) AND (b = 5) AND (a = 5) OR
+                             (a = 1) AND (b = 5) AND (a = 5)) AND
+                            (b = 5) AND (a = 5)
+  => SELECT * FROM t1 WHERE ((FALSE AND (a = 5)) OR
+                             (FALSE AND (b = 5))) AND
+                             (b = 5) AND (a = 5)
+  After this an additional call of remove_eq_conds() converts it
+  to FALSE
+
+  EXAMPLE 2:  
+  SELECT * FROM t1 WHERE (b = 1 OR a = 5) AND (b = 5 AND a = 5 OR 1 != 1);
+  => SELECT * FROM t1 WHERE (b = 1 OR a = 5) AND (b = 5 AND a = 5);
+  => SELECT * FROM t1 WHERE (b = 1 OR a = 5) AND (b = 5) AND (a = 5);
+  => SELECT * FROM t1 WHERE ((b = 1) AND (b = 5) AND (a = 5) OR
+                             (a = 5) AND (b = 5) AND (a = 5)) AND
+                            (b = 5) AND (a = 5)
+  => SELECT * FROM t1 WHERE ((FALSE AND (a = 5)) OR
+                             ((b = 5) AND (a = 5))) AND
+                             (b = 5) AND (a = 5)
+  After this an additional call of  remove_eq_conds() converts it to
+ =>  SELECT * FROM t1 WHERE (b = 5) AND (a = 5)                            
 */
 
 COND *
@@ -13149,9 +13310,11 @@ remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value)
 {
   if (cond->type() == Item::COND_ITEM)
   {
+    List<Item_equal> new_equalities;
     bool and_level= ((Item_cond*) cond)->functype()
       == Item_func::COND_AND_FUNC;
-    List_iterator<Item> li(*((Item_cond*) cond)->argument_list());
+    List<Item> *cond_arg_list= ((Item_cond*) cond)->argument_list();
+    List_iterator<Item> li(*cond_arg_list);
     Item::cond_result tmp_cond_value;
     bool should_fix_fields=0;
 
@@ -13161,92 +13324,72 @@ remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value)
     {
       Item *new_item=remove_eq_conds(thd, item, &tmp_cond_value);
       if (!new_item)
+      {
+        /* This can happen only when item is converted to TRUE or FALSE */
 	li.remove();
+      }
       else if (item != new_item)
       {
-        if (and_level)
-	{
-          /*
-            Take a special care of multiple equality predicates
-            that may be part of 'cond' and 'new_item'.
-            Those multiple equalities that have common members
-            must be merged.
-	  */  
-          Item_cond_and *cond_and= (Item_cond_and *) cond;
-          List<Item_equal> *cond_equal_items=
-            &cond_and->cond_equal.current_level;
-          List<Item> *cond_and_list= cond_and->argument_list();
-
-          if (new_item->type() == Item::COND_ITEM && 
-              ((Item_cond*) new_item)->functype() == Item_func::COND_AND_FUNC)
-          {
-            Item_cond_and *new_item_and= (Item_cond_and *) new_item;
-            List<Item_equal> *new_item_equal_items=
-              &new_item_and->cond_equal.current_level;
-            List<Item> *new_item_and_list= new_item_and->argument_list();
-            cond_and_list->disjoin((List<Item>*) cond_equal_items);
-            new_item_and_list->disjoin((List<Item>*) new_item_equal_items);
-            Item_equal *equal_item;
-            List_iterator<Item_equal> it(*new_item_equal_items);
-	    while ((equal_item= it++))
-	    {
-              equal_item->merge_into_list(cond_equal_items);
-            }
-            if (new_item_and_list->is_empty())
-              li.remove();
-            else
+        /* 
+          This can happen when:
+          - item was an OR formula converted to one disjunct
+          - item was an AND formula converted to one conjunct
+          In these cases the disjunct/conjunct must be merged into the
+          argument list of cond.
+	*/
+        if (new_item->type() == Item::COND_ITEM)
+        {
+          DBUG_ASSERT(((Item_cond *) cond)->functype() == 
+                      ((Item_cond *) new_item)->functype());          
+	  List<Item> *new_item_arg_list=
+            ((Item_cond *) new_item)->argument_list();
+          if (and_level)
+	  {
+            /*
+              If new_item is an AND formula then multiple equalities
+              of new_item_arg_list must merged into multiple equalities
+              of cond_arg_list. 
+	    */
+            List<Item_equal> *new_item_equalities=
+              &((Item_cond_and *) new_item)->cond_equal.current_level;
+            if (!new_item_equalities->is_empty())
 	    {
-              Item *list_item;
-              Item *new_list_item; 
-              uint cnt= new_item_and_list->elements;     
-              List_iterator<Item> it(*new_item_and_list);
-              while ((list_item= it++))
-	      {
-                uchar* is_subst_valid= (uchar *) Item::ANY_SUBST;
-                new_list_item= 
-                  list_item->compile(&Item::subst_argument_checker,
-                                         &is_subst_valid, 
-                                         &Item::equal_fields_propagator,
-                                         (uchar *) &cond_and->cond_equal);
-                if (new_list_item != list_item)
-                  it.replace(new_list_item);
-                new_list_item->update_used_tables();
-              }              
-              li.replace(*new_item_and_list);
-              for (cnt--; cnt; cnt--)
-                item= li++;  
+              /*
+                Cut the multiple equalities from the new_item_arg_list and
+                append them on the list new_equalities. Later the equalities
+                from this list will be merged into the multiple equalities
+                of cond_arg_list all together.
+	      */
+              new_item_arg_list->disjoin((List<Item> *) new_item_equalities);
+              new_equalities.concat(new_item_equalities);
             }
-            cond_and_list->concat((List<Item>*) cond_equal_items); 
           }
-          else if (new_item->type() == Item::FUNC_ITEM && 
-                   ((Item_cond*) new_item)->functype() ==
-                   Item_func::MULT_EQUAL_FUNC)
+          if (new_item_arg_list->is_empty())
+	    li.remove();
+	  else
 	  {
-            cond_and_list->disjoin((List<Item>*) cond_equal_items);
-            ((Item_equal *) new_item)->merge_into_list(cond_equal_items);
-            li.remove();
-            cond_and_list->concat((List<Item>*) cond_equal_items); 
+            uint cnt= new_item_arg_list->elements;
+            li.replace(*new_item_arg_list);
+            /* Make iterator li ignore new items */
+            for (cnt--; cnt; cnt--)
+              li++;
+            should_fix_fields= 1;
           }
-          else
-            li.replace(new_item);
+        }
+        else if (and_level && 
+                 new_item->type() == Item::FUNC_ITEM && 
+                 ((Item_cond*) new_item)->functype() ==
+                  Item_func::MULT_EQUAL_FUNC)
+	{
+          li.remove();
+          new_equalities.push_back((Item_equal *) new_item);
         }
         else
-	{ 
-          if (new_item->type() == Item::COND_ITEM &&
-              ((Item_cond*) new_item)->functype() == 
-              ((Item_cond*) cond)->functype())
-	  {
-            List<Item> *arg_list= ((Item_cond*) new_item)->argument_list();
-            uint cnt= arg_list->elements;
-            li.replace(*arg_list);
-            for ( cnt--; cnt; cnt--)
-              item= li++;
-          }
-	  else
-            li.replace(new_item);
+	{
+          li.replace(new_item);
+          should_fix_fields= 1;
         } 
-	should_fix_fields=1;
-      }
+      }   
       if (*cond_value == Item::COND_UNDEF)
 	*cond_value=tmp_cond_value;
       switch (tmp_cond_value) {
@@ -13272,6 +13415,53 @@ remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value)
 	break; /* purecov: deadcode */
       }
     }
+    if (!new_equalities.is_empty())
+    {
+      DBUG_ASSERT(and_level);
+      /* 
+        Merge multiple equalities that were cut from the results of 
+        simplification of OR formulas converted into AND formulas.
+        These multiple equalities are to be merged into the
+        multiple equalities of  cond_arg_list.
+      */
+      COND_EQUAL *cond_equal= &((Item_cond_and *) cond)->cond_equal;
+      List<Item_equal> *cond_equalities= &cond_equal->current_level;
+      cond_arg_list->disjoin((List<Item> *) cond_equalities);
+      Item_equal *equality;
+      List_iterator_fast<Item_equal> it(new_equalities);
+      while ((equality= it++))
+      {
+        equality->merge_into_list(cond_equalities, false, false);
+        List_iterator_fast<Item_equal> ei(*cond_equalities);
+        while ((equality= ei++))
+	{
+          if (equality->const_item() && !equality->val_int())
+	  {
+            *cond_value= Item::COND_FALSE;
+            return (COND*) 0;
+          }
+        }
+      }
+      cond_arg_list->concat((List<Item> *) cond_equalities);
+      /* 
+        Propagate the newly formed multiple equalities to
+        the all AND/OR levels of cond 
+      */
+      bool is_simplifiable_cond= true;
+      propagate_new_equalities(thd, cond, cond_equalities,
+                               cond_equal->upper_levels,
+                               &is_simplifiable_cond);
+      /*
+        If the above propagation of multiple equalities brings us
+        to multiple equalities that are always FALSE then try to
+        simplify the condition with remove_eq_cond() again.
+      */ 
+      if (is_simplifiable_cond)
+      {
+        if (!(cond= remove_eq_conds(thd, cond, cond_value)))
+          return cond;
+      }          
+    }
     if (should_fix_fields)
       cond->update_used_tables();
 
@@ -13383,6 +13573,7 @@ remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value)
   return cond;					// Point at next and level
 }
 
+
 /**
   Check if equality can be used in removing components of GROUP BY/DISTINCT