Merge for Item_equal.

BitKeeper/etc/ignore:
  auto-union
mysql-test/r/bdb.result:
  Auto merged
mysql-test/r/func_group.result:
  Auto merged
mysql-test/r/innodb.result:
  Auto merged
mysql-test/r/heap_btree.result:
  Auto merged
mysql-test/r/select.result:
  Auto merged
mysql-test/r/user_var.result:
  Auto merged
mysql-test/t/range.test:
  Auto merged
sql/item_func.cc:
  Auto merged
sql/item_func.h:
  Auto merged
sql/item_row.cc:
  Auto merged
sql/item_strfunc.h:
  Auto merged
sql/opt_sum.cc:
  Auto merged
sql/sql_list.h:
  Auto merged
mysql-test/r/func_test.result:
  Post-automerge resolution of conflicts
mysql-test/r/index_merge.result:
  Post-automerge resolution of conflicts
mysql-test/r/join_outer.result:
  Post-automerge resolution of conflicts
mysql-test/r/range.result:
  Post-automerge resolution of conflicts
mysql-test/r/subselect.result:
  Post-automerge resolution of conflicts
sql/item.cc:
  Post-automerge resolution of conflicts
sql/item.h:
  Post-automerge resolution of conflicts
sql/item_cmpfunc.cc:
  Post-automerge resolution of conflicts
sql/item_cmpfunc.h:
  Post-automerge resolution of conflicts
sql/opt_range.cc:
  Post-automerge resolution of conflicts
sql/sql_select.cc:
  Post-automerge resolution of conflicts
sql/sql_select.h:
  Post-automerge resolution of conflicts

.bzrignore

@@ -508,6 +508,7 @@ mysql-test/install_test_db
 mysql-test/mysql-test-run
 mysql-test/ndb/ndbcluster
 mysql-test/r/*.reject
+mysql-test/r/index_merge_load.result
 mysql-test/r/rpl000001.eval
 mysql-test/r/rpl000002.eval
 mysql-test/r/rpl000014.eval
@@ -518,6 +519,7 @@ mysql-test/r/slave-running.eval
 mysql-test/r/slave-stopped.eval
 mysql-test/share/mysql
 mysql-test/std_data/*.pem
+mysql-test/t/index_merge.load
 mysql-test/var/*
 mysql.kdevprj
 mysql.proj

mysql-test/r/func_group.result

@@ -476,7 +476,7 @@ CHI	Los Angeles
 explain
 select max(a3) from t1 where a2 is null and a2 = 2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 select max(a3) from t1 where a2 is null and a2 = 2;
 max(a3)
 NULL

mysql-test/r/func_test.result

@@ -77,7 +77,7 @@ select * from t1 where 1 xor 1;
 a
 explain extended select * from t1 where 1 xor 1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 Warnings:
 Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (1 xor 1)
 select - a from t1;

mysql-test/r/index_merge.result

@@ -76,13 +76,13 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t0	ALL	i1,i2	NULL	NULL	NULL	1024	Using where
 explain select * from t0 where key2 = 45 or key1 is null;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t0	range	i1,i2	i2	4	NULL	1	Using where
+1	SIMPLE	t0	ref	i2	i2	4	const	1	
 explain select * from t0 where key2=10 or key3=3 or key4 <=> null;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t0	index_merge	i2,i3,i4	i2,i3	4,4	NULL	2	Using union(i2,i3); Using where
 explain select * from t0 where key2=10 or key3=3 or key4 is null;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t0	index_merge	i2,i3,i4	i2,i3	4,4	NULL	2	Using union(i2,i3); Using where
+1	SIMPLE	t0	index_merge	i2,i3	i2,i3	4,4	NULL	2	Using where
 explain select key1 from t0 where (key1 <=> null) or (key2 < 5) or 
 (key3=10) or (key4 <=> null);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

mysql-test/r/odbc.result

@@ -12,5 +12,5 @@ select * from t1 where a is null;
 a	b
 explain select * from t1 where b is null;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 drop table t1;

mysql-test/r/range.result

@@ -220,24 +220,22 @@ insert into t1 (x) values (1),(2),(3),(4),(5),(6),(7),(8),(9);
 update t1 set y=x;
 explain select * from t1, t1 t2 where t1.y = 2 and t2.x between 7 and t1.y+0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	y	y	5	const	1	Using where
-1	SIMPLE	t2	range	x	x	5	NULL	4	Using where
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 explain select * from t1, t1 t2 where t1.y = 2 and t2.x >= 7 and t2.x <= t1.y+0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	y	y	5	const	1	Using where
-1	SIMPLE	t2	range	x	x	5	NULL	4	Using where
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 explain select * from t1, t1 t2 where t1.y = 2 and t2.x between t1.y-1 and t1.y+1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	y	y	5	const	1	Using where
-1	SIMPLE	t2	ALL	x	NULL	NULL	NULL	9	Range checked for each record (index map: 0x1)
+1	SIMPLE	t2	range	x	x	5	NULL	3	Using where
 explain select * from t1, t1 t2 where t1.y = 2 and t2.x >= t1.y-1 and t2.x <= t1.y+1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	y	y	5	const	1	Using where
-1	SIMPLE	t2	ALL	x	NULL	NULL	NULL	9	Range checked for each record (index map: 0x1)
+1	SIMPLE	t2	range	x	x	5	NULL	3	Using where
 explain select * from t1, t1 t2 where t1.y = 2 and t2.x between 0 and t1.y;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	y	y	5	const	1	Using where
-1	SIMPLE	t2	ALL	x	NULL	NULL	NULL	9	Using where
+1	SIMPLE	t2	range	x	x	5	NULL	2	Using where
 explain select * from t1, t1 t2 where t1.y = 2 and t2.x >= 0 and t2.x <= t1.y;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	y	y	5	const	1	Using where
@@ -415,14 +413,26 @@ count(*)
 select count(*) from t2;
 count(*)
 1026
+analyze table t1,t2;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	OK
+test.t2	analyze	status	Table is already up to date
 explain select * from t1, t2  where t1.uid=t2.uid AND t1.uid > 0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	uid_index	uid_index	4	NULL	128	Using where
 1	SIMPLE	t2	ref	uid_index	uid_index	4	test.t1.uid	38	
+explain select * from t1, t2  where t1.uid=t2.uid AND t2.uid > 0;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	uid_index	uid_index	4	NULL	128	Using where
+1	SIMPLE	t2	ref	uid_index	uid_index	4	test.t1.uid	38	
 explain select * from t1, t2  where t1.uid=t2.uid AND t1.uid != 0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	uid_index	uid_index	4	NULL	129	Using where
 1	SIMPLE	t2	ref	uid_index	uid_index	4	test.t1.uid	38	
+explain select * from t1, t2  where t1.uid=t2.uid AND t2.uid != 0;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	uid_index	uid_index	4	NULL	129	Using where
+1	SIMPLE	t2	ref	uid_index	uid_index	4	test.t1.uid	38	
 select * from t1, t2  where t1.uid=t2.uid AND t1.uid > 0;
 id	name	uid	id	name	uid
 1001	A	1	1001	A	1

mysql-test/r/select.result

@@ -1375,7 +1375,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr > 0 and t4.companynr > 0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	1199	Using where
-1	SIMPLE	t4	eq_ref	PRIMARY	PRIMARY	1	test.t2.companynr	1	Using where
+1	SIMPLE	t4	eq_ref	PRIMARY	PRIMARY	1	test.t2.companynr	1	
 explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr > 0 or t2.companynr is null;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	

mysql-test/t/range.test

@@ -378,8 +378,12 @@ insert into t2(id, uid, name) select id, uid, name from t1;
 select count(*) from t1;  
 select count(*) from t2;
 
+analyze table t1,t2;
+
 explain select * from t1, t2  where t1.uid=t2.uid AND t1.uid > 0;
+explain select * from t1, t2  where t1.uid=t2.uid AND t2.uid > 0;
 explain select * from t1, t2  where t1.uid=t2.uid AND t1.uid != 0;
+explain select * from t1, t2  where t1.uid=t2.uid AND t2.uid != 0;
 
 select * from t1, t2  where t1.uid=t2.uid AND t1.uid > 0;
 select * from t1, t2  where t1.uid=t2.uid AND t1.uid != 0;

sql/item.cc

@@ -408,6 +408,7 @@ bool DTCollation::aggregate(DTCollation &dt, bool superset_conversion)
 
 Item_field::Item_field(Field *f)
   :Item_ident(NullS, f->table_name, f->field_name),
+   item_equal(0),
    have_privileges(0), any_privileges(0)
 {
   set_field(f);
@@ -418,6 +419,7 @@ Item_field::Item_field(Field *f)
 Item_field::Item_field(THD *thd, Field *f)
   :Item_ident(NullS, thd->strdup(f->table_name), 
               thd->strdup(f->field_name)),
+   item_equal(0),
    have_privileges(0), any_privileges(0)
 {
   set_field(f);
@@ -434,6 +436,7 @@ Item_field::Item_field(THD *thd, Item_field *item)
    any_privileges(item->any_privileges)
 {
   collation.set(DERIVATION_IMPLICIT);
+  item_equal= item->item_equal;
 }
 
 void Item_field::set_field(Field *field_par)
@@ -1582,7 +1585,29 @@ void Item_field::cleanup()
     I.e. we can drop 'field'.
    */
   field= result_field= 0;
-  DBUG_VOID_RETURN;
+}
+
+/*
+  Find a field among specified multiple equalities 
+
+  SYNOPSIS
+    find_item_equal()
+    cond_equal   reference to list of multiple equalities where
+                 the field (this object) is to be looked for
+  
+  DESCRIPTION
+    The function first searches the field among multiple equalities
+    of the current level (in the cond_equal->current_level list).
+    If it fails, it continues searching in upper levels accessed
+    through a pointer cond_equal->upper_levels.
+    The search terminates as soon as a multiple equality containing 
+    the field is found. 
+
+  RETURN VALUES
+    First Item_equal containing the field, if success
+    0, otherwise
+*/
+
 }
 
 void Item::init_make_field(Send_field *tmp_field,

sql/item.h

@@ -90,6 +90,7 @@ class DTCollation {
 };
 
 typedef bool (Item::*Item_processor)(byte *arg);
+typedef Item* (Item::*Item_transformer) (byte *arg);
 
 class Item {
   Item(const Item &);			/* Prevent use of these */
@@ -261,8 +262,15 @@ class Item {
     return (this->*processor)(arg);
   }
 
+   virtual Item* transform(Item_transformer transformer, byte *arg)
+  {
+    return (this->*transformer)(arg);
+  }
+ 
   virtual bool remove_dependence_processor(byte * arg) { return 0; }
   virtual bool remove_fixed(byte * arg) { fixed= 0; return 0; }
+  virtual Item *equal_fields_propagator(byte * arg) { return this; }
+  virtual bool replace_equal_field_processor(byte * arg) { return 0; }
   
   virtual Item *this_item() { return this; } /* For SPs mostly. */
   virtual Item *this_const_item() const { return const_cast<Item*>(this); } /* For SPs mostly. */
@@ -440,6 +448,8 @@ class Item_ident :public Item
                             bool any_privileges, bool allocate_view_names);
 };
 
+class Item_equal;
+class COND_EQUAL;
 
 class Item_field :public Item_ident
 {
@@ -458,7 +468,8 @@ class Item_field :public Item_ident
   Item_field(const char *db_par,const char *table_name_par,
 	     const char *field_name_par)
     :Item_ident(db_par,table_name_par,field_name_par),
-     field(0), result_field(0), have_privileges(0), any_privileges(0)
+     field(0), result_field(0), item_equal(0),}
+     have_privileges(0), any_privileges(0)
   { collation.set(DERIVATION_IMPLICIT); }
   // Constructor need to process subselect with temporary tables (see Item)
   Item_field(THD *thd, Item_field *item);
@@ -498,6 +509,9 @@ class Item_field :public Item_ident
   bool is_null() { return field->is_null(); }
   Item *get_tmp_table_item(THD *thd);
   void cleanup();
+  Item_equal *find_item_equal(COND_EQUAL *cond_equal);
+  Item *equal_fields_propagator(byte *arg);
+  bool replace_equal_field_processor(byte *arg);
   inline uint32 max_disp_length() { return field->max_length(); }
   Item_field *filed_for_view_update() { return this; }
   friend class Item_default_value;
@@ -1173,6 +1187,19 @@ class Item_default_value : public Item_field
     return arg->walk(processor, args) ||
       (this->*processor)(args);
   }
+
+  /* 
+     This method like the walk method traverses the item tree, but
+     at the same time it can replace some nodes in the tree
+  */ 
+  Item *transform(Item_transformer transformer, byte *args)
+  {
+    Item *new_item= arg->transform(transformer, args);
+    if (!new_item)
+      return 0;
+    arg= new_item;
+    return (this->*transformer)(args);
+  }
 };
 
 class Item_insert_value : public Item_field

sql/item_cmpfunc.cc

@@ -256,7 +256,7 @@ void Item_bool_func2::fix_length_and_dec()
       }
     }
   }
-  if (args[1]->type() == FIELD_ITEM)
+  if (args[1]->type() == FIELD_ITEM /* && !args[1]->const_item() */)
   {
     Field *field=((Item_field*) args[1])->field;
     if (field->store_for_compare())
@@ -2008,6 +2008,44 @@ bool Item_cond::walk(Item_processor processor, byte *arg)
   return Item_func::walk(processor, arg);
 }
 
+
+/*
+  Transform an Item_cond object with a transformer callback function
+   
+  SYNOPSIS
+    transform()
+    transformer   the transformer callback function to be applied to the nodes
+                  of the tree of the object
+    arg           parameter to be passed to the transformer
+  
+  DESCRIPTION
+    The function recursively applies the transform method with the
+    same transformer to each member item of the codition list.
+    If the call of the method for a member item returns a new item
+    the old item is substituted for a new one.
+    After this the transform method is applied to the root node
+    of the Item_cond object. 
+     
+  RETURN VALUES
+    Item returned as the result of transformation of the root node 
+*/
+
+Item *Item_cond::transform(Item_transformer transformer, byte *arg)
+{
+  List_iterator<Item> li(list);
+  Item *item;
+  while ((item= li++))
+  {
+    Item *new_item= item->transform(transformer, arg);
+    if (!new_item)
+      return 0;
+    if (new_item != item)
+      li.replace(new_item);
+  }
+  return Item_func::transform(transformer, arg);
+}
+
+
 void Item_cond::split_sum_func(Item **ref_pointer_array, List<Item> &fields)
 {
   List_iterator<Item> li(list);
@@ -2854,3 +2892,289 @@ Item *Item_bool_rowready_func2::negated_item()
   DBUG_ASSERT(0);
   return 0;
 }
+
+Item_equal::Item_equal(Item_field *f1, Item_field *f2)
+  : Item_bool_func(), const_item(0), eval_item(0), cond_false(0)
+{
+  const_item_cache= 0;
+  fields.push_back(f1);
+  fields.push_back(f2);
+}
+
+Item_equal::Item_equal(Item *c, Item_field *f)
+  : Item_bool_func(), eval_item(0), cond_false(0)
+{
+  const_item_cache= 0;
+  fields.push_back(f);
+  const_item= c;
+}
+
+Item_equal::Item_equal(Item_equal *item_equal)
+  : Item_bool_func(), eval_item(0), cond_false(0)
+{
+  const_item_cache= 0;
+  List_iterator_fast<Item_field> li(item_equal->fields);
+  Item_field *item;
+  while ((item= li++))
+  {
+    fields.push_back(item);
+  }
+  const_item= item_equal->const_item;
+  cond_false= item_equal->cond_false;
+}
+
+void Item_equal::add(Item *c)
+{
+  if (cond_false)
+    return;
+  if (!const_item)
+  {
+    const_item= c;
+    return;
+  }
+  Item_func_eq *func= new Item_func_eq(c, const_item);
+  func->set_cmp_func();
+  cond_false =  !(func->val_int());
+}
+
+void Item_equal::add(Item_field *f)
+{
+  fields.push_back(f);
+}
+
+uint Item_equal::members()
+{
+  uint count= 0;
+  List_iterator_fast<Item_field> li(fields);
+  Item_field *item;
+  while ((item= li++))
+    count++;
+  return count;
+}
+
+
+/*
+  Check whether a field is referred in the multiple equality 
+
+  SYNOPSIS
+    contains()
+    field   field whose occurence is to be checked
+  
+  DESCRIPTION
+    The function checks whether field is occured in the Item_equal object 
+    
+  RETURN VALUES
+    1       if nultiple equality contains a reference to field
+    0       otherwise    
+*/
+
+bool Item_equal::contains(Field *field)
+{
+  List_iterator_fast<Item_field> it(fields);
+  Item_field *item;
+  while ((item= it++))
+  {
+    if (field->eq(item->field))
+        return 1;
+  }
+  return 0;
+}
+
+
+/*
+  Join members of another Item_equal object  
+
+  SYNOPSIS
+    merge()
+    item    multiple equality whose members are to be joined
+  
+  DESCRIPTION
+    The function actually merges two multiple equalitis.
+    After this operation the Item_equal object additionally contains
+    the field items of another item of the type Item_equal.
+    If the optional constant items are not equal the cond_false flag is
+    set to 1.  
+       
+  RETURN VALUES
+    none    
+*/
+
+void Item_equal::merge(Item_equal *item)
+{
+  fields.concat(&item->fields);
+  Item *c= item->const_item;
+  if (c)
+  {
+    /* 
+      The flag cond_false will be set to 1 after this, if 
+      the multiple equality already contains a constant and its 
+      value is  not equal to the value of c.
+    */
+    add(const_item);
+  }
+  cond_false|= item->cond_false;
+} 
+
+
+/*
+  Order field items in multiple equality according to a sorting criteria 
+
+  SYNOPSIS
+    sort()
+    cmp          function to compare field item 
+    arg          context extra parameter for the cmp function
+  
+  DESCRIPTION
+    The function perform ordering of the field items in the Item_equal
+    object according to the criteria determined by the cmp callback parameter.
+    If cmp(item_field1,item_field2,arg)<0 than item_field1 must be
+    placed after item_fiel2.
+
+  IMPLEMENTATION
+    The function sorts field items by the exchange sort algorithm.
+    The list of field items is looked through and whenever two neighboring
+    members follow in a wrong order they are swapped. This is performed
+    again and again until we get all members in a right order.
+         
+  RETURN VALUES
+    None    
+*/
+
+void Item_equal::sort(Item_field_cmpfunc cmp, void *arg)
+{
+  bool swap;
+  List_iterator<Item_field> it(fields);
+  do
+  {
+    Item_field *item1= it++;
+    Item_field **ref1= it.ref();
+    Item_field *item2;
+
+    swap= FALSE;
+    while ((item2= it++))
+    {
+      Item_field **ref2= it.ref();
+      if (cmp(item1, item2, arg) < 0)
+      {
+        Item_field *item= *ref1;
+        *ref1= *ref2;
+        *ref2= item;
+        swap= TRUE;
+      }
+      else
+      {
+        item1= item2;
+        ref1= ref2;
+      }
+    }
+    it.rewind();
+  } while (swap);
+}
+
+bool Item_equal::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
+{
+  List_iterator_fast<Item_field> li(fields);
+  Item *item;
+  not_null_tables_cache= used_tables_cache= 0;
+  const_item_cache= 0;
+  while ((item=li++))
+  {
+    table_map tmp_table_map;
+    used_tables_cache|= item->used_tables();
+    tmp_table_map= item->not_null_tables();
+    not_null_tables_cache|= tmp_table_map;
+    if (item->maybe_null)
+      maybe_null=1;
+  }
+  fix_length_and_dec();
+  fixed= 1;
+  return 0;
+}
+
+void Item_equal::update_used_tables()
+{
+  List_iterator_fast<Item_field> li(fields);
+  Item *item;
+  not_null_tables_cache= used_tables_cache= 0;
+  if ((const_item_cache= cond_false))
+    return;
+  while ((item=li++))
+  {
+    item->update_used_tables();
+    used_tables_cache|= item->used_tables();
+    const_item_cache&= item->const_item();
+  }
+}
+
+longlong Item_equal::val_int()
+{
+  if (cond_false)
+    return 0;
+  List_iterator_fast<Item_field> it(fields);
+  Item *item= const_item ? const_item : it++;
+  if ((null_value= item->null_value))
+    return 0;
+  eval_item->store_value(item);
+  while ((item= it++))
+  {
+    if ((null_value= item->null_value) || eval_item->cmp(item))
+      return 0;
+  }
+  return 1;
+}
+
+void Item_equal::fix_length_and_dec()
+{
+  Item *item= const_item ? const_item : get_first();
+  eval_item= cmp_item::get_comparator(item);
+  if (item->result_type() == STRING_RESULT)
+    eval_item->cmp_charset= cmp_collation.collation;
+}
+
+bool Item_equal::walk(Item_processor processor, byte *arg)
+{
+  List_iterator_fast<Item_field> it(fields);
+  Item *item;
+  while ((item= it++))
+    if (item->walk(processor, arg))
+      return 1;
+  return Item_func::walk(processor, arg);
+}
+
+Item *Item_equal::transform(Item_transformer transformer, byte *arg)
+{
+  List_iterator<Item_field> it(fields);
+  Item *item;
+  while ((item= it++))
+  {
+    Item *new_item= item->transform(transformer, arg);
+    if (!new_item)
+      return 0;
+    if (new_item != item)
+      it.replace((Item_field *) new_item);
+  }
+  return Item_func::transform(transformer, arg);
+}
+
+void Item_equal::print(String *str)
+{
+  str->append(func_name());
+  str->append('(');
+  List_iterator_fast<Item_field> it(fields);
+  Item *item;
+  if (const_item)
+    const_item->print(str);
+  else
+  {
+    item= it++;
+    item->print(str);
+  }
+  while ((item= it++))
+  {
+    str->append(',');
+    str->append(' ');
+    item->print(str);
+  }
+  str->append(')');
+}
+

sql/item_cmpfunc.h

@@ -20,6 +20,9 @@
 #ifdef __GNUC__
 #pragma interface			/* gcc class implementation */
 #endif
+#ifdef __GNUC__
+template class List_iterator_fast<Item_field>;
+#endif
 
 extern Item_result item_cmp_type(Item_result a,Item_result b);
 class Item_bool_func2;
@@ -27,6 +30,8 @@ class Arg_comparator;
 
 typedef int (Arg_comparator::*arg_cmp_func)();
 
+typedef int (*Item_field_cmpfunc)(Item_field *f1, Item_field *f2, void *arg); 
+
 class Arg_comparator: public Sql_alloc
 {
   Item **a, **b;
@@ -957,6 +962,7 @@ class Item_cond :public Item_bool_func
   Item_cond(List<Item> &nlist)
     :Item_bool_func(), list(nlist), abort_on_null(0) {}
   bool add(Item *item) { return list.push_back(item); }
+  void add_at_head(List<Item> *nlist) { list.prepand(nlist); }
   bool fix_fields(THD *, struct st_table_list *, Item **ref);
 
   enum Type type() const { return COND_ITEM; }
@@ -969,13 +975,151 @@ class Item_cond :public Item_bool_func
   void top_level_item() { abort_on_null=1; }
   void copy_andor_arguments(THD *thd, Item_cond *item);
   bool walk(Item_processor processor, byte *arg);
+  Item *transform(Item_transformer transformer, byte *arg);
   void neg_arguments(THD *thd);
 };
 
 
+/*
+  The class Item_equal is used to represent conjuctions of equality
+  predicates of the form field1 = field2, and field=const in where
+  conditions and on expressions.
+ 
+  All equality predicates of the form field1=field2 contained in a 
+  conjuction are substituted for a sequence of items of this class.
+  An item of this class Item_equal(f1,f2,...fk) respresents a
+  multiple equality f1=f2=...=fk.
+
+  If a conjuction contains predicates f1=f2 and f2=f3, a new item of
+  this class is created Item_equal(f1,f2,f3) representing the multiple
+  equality f1=f2=f3 that substitutes the above equality predicates in
+  the conjuction.
+  A conjuction of the predicates f2=f1 and f3=f1 and f3=f2 will be
+  substituted for the item representing the same multiple equality
+  f1=f2=f3.
+  An item Item_equal(f1,f2) can appear instead of a conjuction of 
+  f2=f1 and f1=f2, or instead of just the predicate f1=f2.
+
+  An item of the class Item_equal inherites equalities from outer 
+  conjunctive levels.
+
+  Suppose we have a where condition of the following form:
+  WHERE f1=f2 AND f3=f4 AND f3=f5 AND ... AND (...OR (f1=f3 AND ...)).
+  In this case:
+    f1=f2 will be substituted for Item_equal(f1,f2);
+    f3=f4 and f3=f5  will be substituted for Item_equal(f3,f4,f5);
+    f1=f3 will be substituted for Item_equal(f1,f2,f3,f4,f5);
+
+  An object of the class Item_equal can contain an optional constant
+  item c. Thenit represents a multiple equality of the form 
+  c=f1=...=fk.
+
+  Objects of the class Item_equal are used for the following:
+
+  1. An object Item_equal(t1.f1,...,tk.fk) allows us to consider any
+  pair of tables ti and tj as joined by an equi-condition.
+  Thus it provide us with additional access paths from table to table.
+
+  2. An object Item_equal(t1.f1,...,tk.fk) is applied to deduce new
+  SARGable predicates:
+    f1=...=fk AND P(fi) => f1=...=fk AND P(fi) AND P(fj).
+  It also can give us additional index scans and can allow us to
+  improve selectivity estimates.
+
+  3. An object Item_equal(t1.f1,...,tk.fk) is used to optimize the 
+  selected execution plan for the query: if table ti is accessed 
+  before the table tj then in any predicate P in the where condition
+  the occurence of tj.fj is substituted for ti.fi. This can allow
+  an evaluation of the predicate at an earlier step.
+
+  When feature 1 is supported they say that join transitive closure 
+  is employed.
+  When feature 2 is supported they say that search argument transitive
+  closure is employed.
+  Both features are usually supported by preprocessing original query and
+  adding additional predicates.
+  We do not just add predicates, we rather dynamically replace some
+  predicates that can not be used to access tables in the investigated
+  plan for those, obtained by substitution of some fields for equal fields,
+  that can be used.     
+*/
+
+class Item_equal: public Item_bool_func
+{
+  List<Item_field> fields; /* list of equal field items                    */
+  Item *const_item;        /* optional constant item equal to fields items */
+  cmp_item *eval_item;
+  bool cond_false;
+  DTCollation cmp_collation;
+public:
+  inline Item_equal()
+    : Item_bool_func(), const_item(0), eval_item(0), cond_false(0)
+  { const_item_cache=0 ;}
+  Item_equal(Item_field *f1, Item_field *f2);
+  Item_equal(Item *c, Item_field *f);
+  Item_equal(Item_equal *item_equal);
+  inline Item* get_const() { return const_item; }
+  void add(Item *c);
+  void add(Item_field *f);
+  uint members();
+  bool contains(Field *field);
+  Item_field* get_first() { return fields.head(); }
+  void merge(Item_equal *item);
+  enum Functype functype() const { return MULT_EQUAL_FUNC; }
+  longlong val_int(); 
+  const char *func_name() const { return "multiple equal"; }
+  optimize_type select_optimize() const { return OPTIMIZE_EQUAL; }
+  void sort(Item_field_cmpfunc cmp, void *arg);
+  friend class Item_equal_iterator;
+  void fix_length_and_dec();
+  bool fix_fields(THD *thd, TABLE_LIST *tables, Item **ref);
+  void update_used_tables();
+  bool walk(Item_processor processor, byte *arg);
+  Item *transform(Item_transformer transformer, byte *arg);
+  void print(String *str);
+  CHARSET_INFO *compare_collation() 
+  { return fields.head()->collation.collation; }
+}; 
+
+class COND_EQUAL
+{
+public:
+  uint max_members;               /* max number of members the current level
+                                     list and all lower level lists */ 
+  COND_EQUAL *upper_levels;       /* multiple equalities of upper and levels */
+  List<Item_equal> current_level; /* list of multiple equalities of 
+                                     the current and level           */
+  COND_EQUAL()
+  { 
+    max_members= 0;
+    upper_levels= 0;
+  }
+};
+
+
+class Item_equal_iterator :List_iterator_fast<Item_field>
+{
+public:
+  inline Item_equal_iterator(Item_equal &item_equal) 
+    :List_iterator_fast<Item_field> (item_equal.fields)
+  {}
+  inline Item_field* operator++(int)
+  { 
+    Item_field *item= (*(List_iterator_fast<Item_field> *) this)++;
+    return  item;
+  }
+  inline void rewind(void) 
+  { 
+    List_iterator_fast<Item_field>::rewind();
+  }
+};
+
 class Item_cond_and :public Item_cond
 {
 public:
+  COND_EQUAL cond_equal;  /* contains list of Item_equal objects for 
+                             the current and level and reference
+                             to multiple equalities of upper and levels */  
   Item_cond_and() :Item_cond() {}
   Item_cond_and(Item *i1,Item *i2) :Item_cond(i1,i2) {}
   Item_cond_and(THD *thd, Item_cond_and *item) :Item_cond(thd, item) {}

sql/item_func.cc

@@ -260,6 +260,45 @@ bool Item_func::walk (Item_processor processor, byte *argument)
   return (this->*processor)(argument);
 }
 
+
+/*
+  Transform an Item_func object with a transformer callback function
+   
+  SYNOPSIS
+    transform()
+    transformer   the transformer callback function to be applied to the nodes
+                  of the tree of the object
+    argument      parameter to be passed to the transformer
+  
+  DESCRIPTION
+    The function recursively applies the transform method with the
+    same transformer to each argument the function.
+    If the call of the method for a member item returns a new item
+    the old item is substituted for a new one.
+    After this the transform method is applied to the root node
+    of the Item_func object. 
+     
+  RETURN VALUES
+    Item returned as the result of transformation of the root node 
+*/
+
+Item *Item_func::transform(Item_transformer transformer, byte *argument)
+{
+  if (arg_count)
+  {
+    Item **arg,**arg_end;
+    for (arg= args, arg_end= args+arg_count; arg != arg_end; arg++)
+    {
+      Item *new_item= (*arg)->transform(transformer, argument);
+      if (!new_item)
+	return 0;
+      *arg= new_item;
+    }
+  }
+  return (this->*transformer)(argument);
+}
+
+
 void Item_func::split_sum_func(Item **ref_pointer_array, List<Item> &fields)
 {
   Item **arg, **arg_end;

sql/item_func.h

@@ -40,7 +40,8 @@ class Item_func :public Item_result_field
   enum Functype { UNKNOWN_FUNC,EQ_FUNC,EQUAL_FUNC,NE_FUNC,LT_FUNC,LE_FUNC,
 		  GE_FUNC,GT_FUNC,FT_FUNC,
 		  LIKE_FUNC,NOTLIKE_FUNC,ISNULL_FUNC,ISNOTNULL_FUNC,
-		  COND_AND_FUNC, COND_OR_FUNC, COND_XOR_FUNC, BETWEEN, IN_FUNC,
+		  COND_AND_FUNC, COND_OR_FUNC, COND_XOR_FUNC,
+                  BETWEEN, IN_FUNC, MULT_EQUAL_FUNC,
 		  INTERVAL_FUNC, ISNOTNULLTEST_FUNC,
 		  SP_EQUALS_FUNC, SP_DISJOINT_FUNC,SP_INTERSECTS_FUNC,
 		  SP_TOUCHES_FUNC,SP_CROSSES_FUNC,SP_WITHIN_FUNC,
@@ -50,7 +51,8 @@ class Item_func :public Item_result_field
                   NOT_FUNC, NOT_ALL_FUNC,
                   NOW_FUNC, TRIG_COND_FUNC,
                   GUSERVAR_FUNC};
-  enum optimize_type { OPTIMIZE_NONE,OPTIMIZE_KEY,OPTIMIZE_OP, OPTIMIZE_NULL };
+  enum optimize_type { OPTIMIZE_NONE,OPTIMIZE_KEY,OPTIMIZE_OP, OPTIMIZE_NULL,
+                       OPTIMIZE_EQUAL };
   enum Type type() const { return FUNC_ITEM; }
   virtual enum Functype functype() const   { return UNKNOWN_FUNC; }
   Item_func(void):
@@ -150,6 +152,7 @@ class Item_func :public Item_result_field
                                          bool allow_superset_comversion= FALSE);
 
   bool walk(Item_processor processor, byte *arg);
+  Item *transform(Item_transformer transformer, byte *arg);
 };
 
 

sql/item_row.cc

@@ -145,6 +145,18 @@ bool Item_row::walk(Item_processor processor, byte *arg)
   return (this->*processor)(arg);
 }
 
+Item *Item_row::transform(Item_transformer transformer, byte *arg)
+{
+  for (uint i= 0; i < arg_count; i++)
+  {
+    Item *new_item= items[i]->transform(transformer, arg);
+    if (!new_item)
+      return 0;
+    items[i]= new_item;
+  }
+  return (this->*transformer)(arg);
+}
+
 void Item_row::bring_value()
 {
   for (uint i= 0; i < arg_count; i++)

sql/item_row.h

@@ -65,6 +65,7 @@ class Item_row: public Item
   void print(String *str);
 
   bool walk(Item_processor processor, byte *arg);
+  Item *transform(Item_transformer transformer, byte *arg);
 
   uint cols() { return arg_count; }
   Item* el(uint i) { return items[i]; }

sql/item_strfunc.h

@@ -428,6 +428,14 @@ class Item_func_make_set :public Item_str_func
     return item->walk(processor, arg) ||
       Item_str_func::walk(processor, arg);
   }
+  Item *transform(Item_transformer transformer, byte *arg)
+  {
+    Item *new_item= item->transform(transformer, arg);
+    if (!new_item)
+      return 0;
+    item= new_item;
+    return Item_str_func::transform(transformer, arg);
+  }
   void print(String *str);
 };
 

sql/opt_range.cc

@@ -3148,12 +3148,98 @@ QUICK_SELECT_I *TRP_ROR_UNION::make_quick(PARAM *param,
   DBUG_RETURN(quick_roru);
 }
 
-/****************************************************************************/
+
+/*
+  Build a SEL_TREE for a simple predicate
+ 
+  SYNOPSIS
+    get_func_mm_tree()
+      param       PARAM from SQL_SELECT::test_quick_select
+      cond_func   item for the predicate
+      field       field in the predicate
+      value       constant in the predicate
+      cmp_type    compare type for the field
+
+  RETURN 
+    Pointer to thre built tree
+*/
+
+static SEL_TREE *get_func_mm_tree(PARAM *param, Item_func *cond_func, 
+                                  Field *field, Item *value,
+                                  Item_result cmp_type)
+{
+  SEL_TREE *tree= 0;
+  DBUG_ENTER("get_func_mm_tree");
+
+  switch (cond_func->functype()) {
+  case Item_func::NE_FUNC:
+    tree= get_mm_parts(param, cond_func, field, Item_func::LT_FUNC,
+		       value, cmp_type);
+    if (tree)
+    {
+      tree= tree_or(param, tree, get_mm_parts(param, cond_func, field,
+					      Item_func::GT_FUNC,
+					      value, cmp_type));
+    }
+    break;
+  case Item_func::BETWEEN:
+    tree= get_mm_parts(param, cond_func, field, Item_func::GE_FUNC,
+		       cond_func->arguments()[1],cmp_type);
+    if (tree)
+    {
+      tree= tree_and(param, tree, get_mm_parts(param, cond_func, field,
+					       Item_func::LE_FUNC,
+					       cond_func->arguments()[2],
+                                               cmp_type));
+    }
+    break;
+  case Item_func::IN_FUNC:
+  {
+    Item_func_in *func=(Item_func_in*) cond_func;
+    tree= get_mm_parts(param, cond_func, field, Item_func::EQ_FUNC,
+                       func->arguments()[1], cmp_type);
+    if (tree)
+    {
+      Item **arg, **end;
+      for (arg= func->arguments()+2, end= arg+func->argument_count()-2;
+           arg < end ; arg++)
+      {
+        tree=  tree_or(param, tree, get_mm_parts(param, cond_func, field, 
+                                                 Item_func::EQ_FUNC,
+                                                 *arg,
+                                                 cmp_type));
+      }
+    }
+    break;
+  }
+  default: 
+  {
+    /* 
+       Here the function for the following predicates are processed:
+       <, <=, =, >=, >, LIKE, IS NULL, IS NOT NULL.
+       If the predicate is of the form (value op field) it is handled
+       as the equivalent predicate (field rev_op value), e.g.
+       2 <= a is handled as a >= 2.
+    */
+    Item_func::Functype func_type=
+      (value != cond_func->arguments()[0]) ? cond_func->functype() :
+        ((Item_bool_func2*) cond_func)->rev_functype();
+    tree= get_mm_parts(param, cond_func, field, func_type, value, cmp_type);
+  }
+  }
+
+  DBUG_RETURN(tree);
+
+}
+
 	/* make a select tree of all keys in condition */
 
 static SEL_TREE *get_mm_tree(PARAM *param,COND *cond)
 {
   SEL_TREE *tree=0;
+  SEL_TREE *ftree= 0;
+  Item_field *field_item= 0;
+  Item *value;
   DBUG_ENTER("get_mm_tree");
 
   if (cond->type() == Item::COND_ITEM)
@@ -3201,9 +3287,12 @@ static SEL_TREE *get_mm_tree(PARAM *param,COND *cond)
     DBUG_RETURN(new SEL_TREE(SEL_TREE::IMPOSSIBLE));
   }
 
-  table_map ref_tables=cond->used_tables();
+  table_map ref_tables= 0;
+  table_map param_comp= ~(param->prev_tables | param->read_tables |
+		          param->current_table);
   if (cond->type() != Item::FUNC_ITEM)
   {						// Should be a field
+    ref_tables= cond->used_tables();
     if ((ref_tables & param->current_table) ||
 	(ref_tables & ~(param->prev_tables | param->read_tables)))
       DBUG_RETURN(0);
@@ -3214,80 +3303,42 @@ static SEL_TREE *get_mm_tree(PARAM *param,COND *cond)
   if (cond_func->select_optimize() == Item_func::OPTIMIZE_NONE)
     DBUG_RETURN(0);				// Can't be calculated
 
-  param->cond= cond;
-
-  if (cond_func->functype() == Item_func::BETWEEN)
+  switch (cond_func->functype()) {
+  case Item_func::BETWEEN:
+    if (cond_func->arguments()[0]->type() != Item::FIELD_ITEM)
+      DBUG_RETURN(0);
+    field_item= (Item_field*) (cond_func->arguments()[0]);
+    value= NULL;
+    break;
+  case Item_func::IN_FUNC:
   {
-    if (cond_func->arguments()[0]->type() == Item::FIELD_ITEM)
-    {
-      Field *field=((Item_field*) (cond_func->arguments()[0]))->field;
-      Item_result cmp_type=field->cmp_type();
-      DBUG_RETURN(tree_and(param,
-			   get_mm_parts(param, cond_func, field,
-					Item_func::GE_FUNC,
-					cond_func->arguments()[1], cmp_type),
-			   get_mm_parts(param, cond_func, field,
-					Item_func::LE_FUNC,
-					cond_func->arguments()[2], cmp_type)));
-    }
-    DBUG_RETURN(0);
-  }
-  if (cond_func->functype() == Item_func::IN_FUNC)
-  {						// COND OR
     Item_func_in *func=(Item_func_in*) cond_func;
-    if (func->key_item()->type() == Item::FIELD_ITEM)
+    if (func->key_item()->type() != Item::FIELD_ITEM)
+      DBUG_RETURN(0);
+    field_item= (Item_field*) (func->key_item());
+    value= NULL;
+    break;
+  }
+  case Item_func::MULT_EQUAL_FUNC:
+  {
+    Item_equal *item_equal= (Item_equal *) cond;    
+    if (!(value= item_equal->get_const()))
+      DBUG_RETURN(0);
+    Item_equal_iterator it(*item_equal);
+    ref_tables= value->used_tables();
+    while ((field_item= it++))
     {
-      Field *field=((Item_field*) (func->key_item()))->field;
-      Item_result cmp_type=field->cmp_type();
-      tree= get_mm_parts(param,cond_func,field,Item_func::EQ_FUNC,
-			 func->arguments()[1],cmp_type);
-      if (!tree)
-	DBUG_RETURN(tree);			// Not key field
-      for (uint i=2 ; i < func->argument_count(); i++)
+      Field *field= field_item->field;
+      Item_result cmp_type= field->cmp_type();
+      if (!((ref_tables | field->table->map) & param_comp))
       {
-	SEL_TREE *new_tree=get_mm_parts(param,cond_func,field,
-					Item_func::EQ_FUNC,
-					func->arguments()[i],cmp_type);
-	tree=tree_or(param,tree,new_tree);
+        tree= get_mm_parts(param, cond, field, Item_func::EQ_FUNC,
+		           value,cmp_type);
+        ftree= !ftree ? tree : tree_and(param, ftree, tree);
       }
-      DBUG_RETURN(tree);
     }
-    DBUG_RETURN(0);				// Can't optimize this IN
-  }
-
-  if (ref_tables & ~(param->prev_tables | param->read_tables |
-		     param->current_table))
-    DBUG_RETURN(0);				// Can't be calculated yet
-  if (!(ref_tables & param->current_table))
-    DBUG_RETURN(new SEL_TREE(SEL_TREE::MAYBE)); // This may be FALSE or TRUE
-
-  /* check field op const */
-  /* btw, ft_func's arguments()[0] isn't FIELD_ITEM.  SerG*/
-  if (cond_func->arguments()[0]->type() == Item::FIELD_ITEM)
-  {
-    tree= get_mm_parts(param, cond_func,
-		       ((Item_field*) (cond_func->arguments()[0]))->field,
-		       cond_func->functype(),
-		       cond_func->arg_count > 1 ? cond_func->arguments()[1] :
-		       0,
-		       ((Item_field*) (cond_func->arguments()[0]))->field->
-		       cmp_type());
-  }
-  /* check const op field */
-  if (!tree &&
-      cond_func->have_rev_func() &&
-      cond_func->arguments()[1]->type() == Item::FIELD_ITEM)
-  {
-    DBUG_RETURN(get_mm_parts(param, cond_func,
-			     ((Item_field*)
-			      (cond_func->arguments()[1]))->field,
-			     ((Item_bool_func2*) cond_func)->rev_functype(),
-			     cond_func->arguments()[0],
-			     ((Item_field*)
-			      (cond_func->arguments()[1]))->field->cmp_type()
-			     ));
-  }
-  DBUG_RETURN(tree);
+    
+    DBUG_RETURN(ftree);
 }
 
 
@@ -3296,17 +3347,10 @@ get_mm_parts(PARAM *param, COND *cond_func, Field *field,
 	     Item_func::Functype type,
 	     Item *value, Item_result cmp_type)
 {
-  bool ne_func= FALSE;
   DBUG_ENTER("get_mm_parts");
   if (field->table != param->table)
     DBUG_RETURN(0);
 
-  if (type == Item_func::NE_FUNC)
-  {
-    ne_func= TRUE;
-    type= Item_func::LT_FUNC;
-  }
-
   KEY_PART *key_part = param->key_parts;
   KEY_PART *end = param->key_parts_end;
   SEL_TREE *tree=0;
@@ -3344,15 +3388,6 @@ get_mm_parts(PARAM *param, COND *cond_func, Field *field,
     }
   }
 
-  if (ne_func)
-  {
-    SEL_TREE *tree2= get_mm_parts(param, cond_func,
-				  field, Item_func::GT_FUNC,
-                                  value, cmp_type);
-    if (tree2)
-      tree= tree_or(param,tree,tree2);
-  }
-
   DBUG_RETURN(tree);
 }
 

sql/opt_sum.cc

@@ -341,6 +341,18 @@ static bool simple_pred(Item_func *func_item, Item **args, bool *inv_order)
   Item *item;
   *inv_order= 0;
   switch (func_item->argument_count()) {
+  case 0:
+    /* MULT_EQUAL_FUNC */
+    {
+      Item_equal *item_equal= (Item_equal *) func_item;
+      Item_equal_iterator it(*item_equal);
+      args[0]= it++;
+      if (it++)
+        return 0;
+      if (!(args[1]= item_equal->get_const()))
+        return 0;
+    }
+    break;
   case 1:
     /* field IS NULL */
     item= func_item->arguments()[0];
@@ -481,6 +493,9 @@ static bool matching_cond(bool max_fl, TABLE_REF *ref, KEY *keyinfo,
   case Item_func::BETWEEN:
     between= 1;
     break;
+  case Item_func::MULT_EQUAL_FUNC:
+    eq_type= 1;
+    break;
   default:
     return 0;                                        // Can't optimize function
   }

sql/sql_list.h

@@ -127,10 +127,12 @@ class base_list :public Sql_alloc
   void remove(list_node **prev)
   {
     list_node *node=(*prev)->next;
-    delete *prev;
-    *prev=node;
     if (!--elements)
       last= &first;
+    else if (last == &(*prev)->next)
+      last= prev;
+    delete *prev;
+    *prev=node;
   }
   inline void *pop(void)
   {
@@ -143,9 +145,36 @@ class base_list :public Sql_alloc
   }
   inline void concat(base_list *list)
   {
-    *last= list->first;
-    last= list->last;
-    elements+= list->elements;
+    if (!list->is_empty())
+    {
+      *last= list->first;
+      last= list->last;
+      elements+= list->elements;
+    }
+  }
+  inline void disjoin(base_list *list)
+  {
+    list_node **prev= &first;
+    list_node *node= first;
+    list_node *list_first= list->first;
+    elements=0;
+    while (node && node != list_first)
+    {
+      prev= &node->next;
+      node= node->next;
+      elements++;
+    }
+    *prev= *last;
+    last= prev;
+  }
+  inline void prepand(base_list *list)
+  {
+    if (!list->is_empty())
+    {
+      *list->last= first;
+      first= list->first;
+      elements+= list->elements;
+    }
   }
   inline list_node* last_node() { return *last; }
   inline list_node* first_node() { return first;}
@@ -257,6 +286,9 @@ template <class T> class List :public base_list
   inline T* head() {return (T*) base_list::head(); }
   inline T** head_ref() {return (T**) base_list::head_ref(); }
   inline T* pop()  {return (T*) base_list::pop(); }
+  inline void concat(List<T> *list) { base_list::concat(list); }
+  inline void disjoin(List<T> *list) { base_list::disjoin(list); }
+  inline void prepand(List<T> *list) { base_list::prepand(list); }
   void delete_elements(void)
   {
     list_node *element,*next;
@@ -267,7 +299,6 @@ template <class T> class List :public base_list
     }
     empty();
   }
-  inline void concat(List<T> *list) { base_list::concat(list); }
 };
 
 
@@ -278,6 +309,8 @@ template <class T> class List_iterator :public base_list_iterator
   inline T* operator++(int) { return (T*) base_list_iterator::next(); }
   inline T *replace(T *a)   { return (T*) base_list_iterator::replace(a); }
   inline T *replace(List<T> &a) { return (T*) base_list_iterator::replace(a); }
+  inline void rewind(void)  { base_list_iterator::rewind(); }
+  inline void remove()      { base_list_iterator::remove(); }
   inline void after(T *a)   { base_list_iterator::after(a); }
   inline T** ref(void)	    { return (T**) base_list_iterator::ref(); }
 };

sql/sql_select.cc

@@ -43,6 +43,7 @@ static bool make_join_statistics(JOIN *join,TABLE_LIST *tables,COND *conds,
 static bool update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,
 				JOIN_TAB *join_tab,
                                 uint tables, COND *conds,
+                                COND_EQUAL *cond_equal,
 				table_map table_map, SELECT_LEX *select_lex);
 static int sort_keyuse(KEYUSE *a,KEYUSE *b);
 static void set_position(JOIN *join,uint index,JOIN_TAB *table,KEYUSE *key);
@@ -90,6 +91,11 @@ static int return_zero_rows(JOIN *join, select_result *res,TABLE_LIST *tables,
 			    uint select_options, const char *info,
 			    Item *having, Procedure *proc,
 			    SELECT_LEX_UNIT *unit);
+static COND *build_all_equal_items(COND *cond,
+                                        COND_EQUAL *inherited);
+static COND* substitute_for_best_equal_field(COND *cond,
+                                             COND_EQUAL *cond_equal,
+                                             void *table_join_idx);
 static COND *simplify_joins(JOIN *join, List<TABLE_LIST> *join_list,
                             COND *conds, bool top);
 static COND *optimize_cond(JOIN *join, COND *conds,
@@ -525,6 +531,52 @@ JOIN::optimize()
   }
 #endif
 
+  /* Eliminate NOT operators */
+  conds= eliminate_not_funcs(conds);
+  DBUG_EXECUTE("where", print_where(conds, "after negation elimination"););
+  {
+    TABLE_LIST *tables;
+    for (tables= tables_list; tables; tables= tables->next)
+    { 
+      if (tables->on_expr)
+        tables->on_expr= eliminate_not_funcs(tables->on_expr);
+    }
+  }
+
+  /* 
+    Build all multiple equality predicates and eliminate equality
+    predicates that can be inferred from these multiple equalities.
+    For each reference of a field included into a multiple equality
+    that occurs in a function set a pointer to the multiple equality
+    predicate. Substitute a constant instead of this field if the
+    multiple equality contains a constant.
+  */
+  if (conds) 
+  {
+    conds= build_all_equal_items(conds, NULL);
+    conds->update_used_tables();
+    if (conds->type() == Item::COND_ITEM &&
+        ((Item_cond*) conds)->functype() == Item_func::COND_AND_FUNC)
+      cond_equal= &((Item_cond_and*) conds)->cond_equal;
+    else if (conds->type() == Item::FUNC_ITEM &&
+             ((Item_cond*) conds)->functype() == Item_func::MULT_EQUAL_FUNC)
+    {
+      cond_equal= new COND_EQUAL;
+      cond_equal->current_level.push_back((Item_equal *) conds);
+    }
+  }
+  {
+    TABLE_LIST *tables;
+    for (tables= tables_list; tables; tables= tables->next)
+    { 
+      if (tables->on_expr)
+      {
+        tables->on_expr= build_all_equal_items(tables->on_expr, cond_equal);
+        tables->on_expr->update_used_tables();  
+      }
+    }
+  }
+
   conds= optimize_cond(this, conds,&cond_value);   
   if (thd->net.report_error)
   {
@@ -617,7 +669,31 @@ JOIN::optimize()
   if (const_tables && !thd->locked_tables &&
       !(select_options & SELECT_NO_UNLOCK))
     mysql_unlock_some_tables(thd, table, const_tables);
-
+  /*
+    Among the equal fields belonging to the same multiple equality
+    choose the one that is to be retrieved first and substitute
+    all references to these in where condition for a reference for
+    the selected field.
+  */
+  if (conds)
+  {
+    conds= substitute_for_best_equal_field(conds, cond_equal, map2table);
+    conds->update_used_tables();
+  }
+  {
+    TABLE_LIST *tables;
+    for (tables= tables_list; tables; tables= tables->next)
+    { 
+      if (tables->on_expr)
+      {
+        tables->on_expr= substitute_for_best_equal_field(tables->on_expr,
+                                                         cond_equal,
+                                                         map2table);
+        tables->on_expr->update_used_tables();
+        map2table[tables->table->tablenr]->on_expr= tables->on_expr;
+      }
+    }
+  }
   if (!conds && outer_join)
   {
     /* Handle the case where we have an OUTER JOIN without a WHERE */
@@ -2150,7 +2226,8 @@ make_join_statistics(JOIN *join,TABLE_LIST *tables,COND *conds,
 
   if (conds || outer_join)
     if (update_ref_and_keys(join->thd, keyuse_array, stat, join->tables,
-                            conds, ~outer_join, join->select_lex))
+                            conds, join->cond_equal,
+                            ~outer_join, join->select_lex))
       DBUG_RETURN(1);
 
   /* Read tables with 0 or 1 rows (system tables) */
@@ -2482,6 +2559,7 @@ merge_key_fields(KEY_FIELD *start,KEY_FIELD *new_fields,KEY_FIELD *end,
     add_key_field()
     key_fields			Pointer to add key, if usable
     and_level			And level, to be stored in KEY_FIELD
+    cond                        Condition predicate
     field			Field used in comparision
     eq_func			True if we used =, <=> or IS NULL
     value			Value used for comparison with field
@@ -2497,8 +2575,8 @@ merge_key_fields(KEY_FIELD *start,KEY_FIELD *new_fields,KEY_FIELD *end,
 */
 
 static void
-add_key_field(KEY_FIELD **key_fields,uint and_level, COND *cond,
-	      Field *field,bool eq_func,Item **value, uint num_values,
+add_key_field(KEY_FIELD **key_fields, uint and_level, COND *cond,
+	      Field *field, bool eq_func, Item **value, uint num_values,
 	      table_map usable_tables)
 {
   uint exists_optimize= 0;
@@ -2603,6 +2681,57 @@ add_key_field(KEY_FIELD **key_fields,uint and_level, COND *cond,
 }
 
 
+/*
+  Add possible keys to array of possible keys originated from a simple predicate
+
+  SYNPOSIS
+    add_key_equal_fields()
+    key_fields			Pointer to add key, if usable
+    and_level			And level, to be stored in KEY_FIELD
+    cond                        Condition predicate
+    field			Field used in comparision
+    eq_func			True if we used =, <=> or IS NULL
+    value			Value used for comparison with field
+				Is NULL for BETWEEN and IN    
+    usable_tables		Tables which can be used for key optimization
+
+  NOTES
+    If field items f1 and f2 belong to the same multiple equality and
+    a key is added for f1, the the same key is added for f2.
+
+  RETURN
+    *key_fields is incremented if we stored a key in the array
+*/
+
+static void
+add_key_equal_fields(KEY_FIELD **key_fields, uint and_level,
+                     COND *cond, Item_field *field_item,
+                     bool eq_func, Item **val,
+                     uint num_values, table_map usable_tables)
+{
+  Field *field= field_item->field;
+  add_key_field(key_fields, and_level, cond, field,
+                eq_func, val, num_values, usable_tables);
+  Item_equal *item_equal= field_item->item_equal;
+  if (item_equal)
+  { 
+    /*
+      Add to the set of possible key values every substitution of
+      the field for an equal field included into item_equal
+    */
+    Item_equal_iterator it(*item_equal);
+    Item_field *item;
+    while ((item= it++))
+    {
+      if (!field->eq(item->field))
+      {
+        add_key_field(key_fields, and_level, cond, item->field,
+                      eq_func, val, num_values, usable_tables);
+      }
+    }
+  }
+}
+
 static void
 add_key_fields(JOIN_TAB *stat,KEY_FIELD **key_fields,uint *and_level,
 	       COND *cond, table_map usable_tables)
@@ -2663,21 +2792,19 @@ add_key_fields(JOIN_TAB *stat,KEY_FIELD **key_fields,uint *and_level,
     if (cond_func->arguments()[0]->real_item()->type() == Item::FIELD_ITEM &&
 	!(cond_func->arguments()[0]->used_tables() & OUTER_REF_TABLE_BIT))
     {
-      add_key_field(key_fields,*and_level,cond_func,
-		    ((Item_field*) (cond_func->arguments()[0])->real_item())
-		    ->field,
-		    equal_func,
-                    cond_func->arguments()+1, 1, usable_tables);
+      add_key_equal_fields(key_fields, *and_level, cond_func,
+	                (Item_field*) (cond_func->arguments()[0])->real_item(),
+		           equal_func,
+		           cond_func->arguments()+1, 1, usable_tables);
     }
     if (cond_func->arguments()[1]->real_item()->type() == Item::FIELD_ITEM &&
 	cond_func->functype() != Item_func::LIKE_FUNC &&
 	!(cond_func->arguments()[1]->used_tables() & OUTER_REF_TABLE_BIT))
     {
-      add_key_field(key_fields,*and_level,cond_func,
-		    ((Item_field*) (cond_func->arguments()[1])->real_item())
-		    ->field,
-		    equal_func,
-		    cond_func->arguments(),1,usable_tables);
+      add_key_equal_fields(key_fields, *and_level, cond_func, 
+                       (Item_field*) (cond_func->arguments()[1])->real_item(),
+		           equal_func,
+		           cond_func->arguments(),1,usable_tables);
     }
     break;
   }
@@ -2689,15 +2816,55 @@ add_key_fields(JOIN_TAB *stat,KEY_FIELD **key_fields,uint *and_level,
       Item *tmp=new Item_null;
       if (unlikely(!tmp))                       // Should never be true
 	return;
-      add_key_field(key_fields,*and_level,cond_func,
-		    ((Item_field*) (cond_func->arguments()[0])->real_item())
-		    ->field,
+      add_key_equal_fields(key_fields, *and_level, cond_func,
+		    (Item_field*) (cond_func->arguments()[0])->real_item(),
 		    cond_func->functype() == Item_func::ISNULL_FUNC,
 		    &tmp, 1, usable_tables);
     }
     break;
+  case Item_func::OPTIMIZE_EQUAL:
+    Item_equal *item_equal= (Item_equal *) cond;
+    Item *const_item= item_equal->get_const();
+    Item_equal_iterator it(*item_equal);
+    Item_field *item;
+    if (const_item)
+    {
+      /*
+        For each field field1 from item_equal consider the equality 
+        field1=const_item as a condition allowing an index access of the table
+        with field1 by the keys value of field1.
+      */   
+      while ((item= it++))
+      {
+        add_key_field(key_fields, *and_level, cond, item->field,
+                      TRUE, &const_item, 1, usable_tables);
+      }
+    }
+    else 
+    {
+      /*
+        Consider all pairs of different fields included into item_equal.
+        For each of them (field1, field1) consider the equality 
+        field1=field2 as a condition allowing an index access of the table
+        with field1 by the keys value of field2.
+      */   
+      Item_equal_iterator fi(*item_equal);
+      while ((item= fi++))
+      {
+        Field *field= item->field;
+        while ((item= it++))
+        {
+          if (!field->eq(item->field))
+          {
+            add_key_field(key_fields, *and_level, cond, field,
+                          TRUE, (Item **) &item, 1, usable_tables);
+          }
+        }
+        it.rewind();
+      }
+    }
+    break;
   }
-  return;
 }
 
 /*
@@ -2840,15 +3007,19 @@ sort_keyuse(KEYUSE *a,KEYUSE *b)
 
 static bool
 update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,JOIN_TAB *join_tab,
-		    uint tables, COND *cond, table_map normal_tables,
-		    SELECT_LEX *select_lex)
+		    uint tables, COND *cond, COND_EQUAL *cond_equal,
+                    table_map normal_tables, SELECT_LEX *select_lex)
 {
   uint	and_level,i,found_eq_constant;
   KEY_FIELD *key_fields, *end, *field;
+  uint m= 1;
+  
+  if (cond_equal && cond_equal->max_members)
+    m= cond_equal->max_members;
 
   if (!(key_fields=(KEY_FIELD*)
 	thd->alloc(sizeof(key_fields[0])*
-		   (thd->lex->current_select->cond_count+1)*2)))
+		   (thd->lex->current_select->cond_count+1)*2*m)))
     return TRUE; /* purecov: inspected */
   and_level= 0;
   field= end= key_fields;
@@ -4953,7 +5124,7 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
       }
 
       COND *tmp=make_cond_for_table(cond,used_tables,current_map);
-      if (!tmp && tab->quick)
+      if (!tmp && tab->quick && tab->type == JT_ALL)
       {						// Outer join
         if (tab->type != JT_ALL)
         {
@@ -5757,6 +5928,668 @@ template class List<Item_func_match>;
 template class List_iterator<Item_func_match>;
 #endif
 
+
+/* 
+  Find the multiple equality predicate containing a field
+ 
+  SYNOPSIS
+    find_item_equal()
+    cond_equal          multiple equalities to search in
+    field               field to look for
+    inherited_fl  :out  set up to TRUE iff multiple equality is found
+                        on upper levels (not on current level of cond_equal) 
+
+  DESCRIPTION
+    The function retrieves the multiple equalities accessed through
+    the con_equal structure from current level and up looking for
+    an equality containing field. It stops retrieval as soon as the equality
+    is found and set up inherited_fl to TRUE if it's found on upper levels.
+
+  RETURN
+    Item_equal for the found multiple equality predicate if a success;
+    NULL - otherwise.
+*/
+
+Item_equal *find_item_equal(COND_EQUAL *cond_equal, Field *field,
+                            bool *inherited_fl)
+{
+  Item_equal *item= 0;
+  bool in_upper_level= FALSE;
+  while (cond_equal)
+  {
+    List_iterator_fast<Item_equal> li(cond_equal->current_level);
+    while ((item= li++))
+    {
+      if (item->contains(field))
+        goto finish;
+    }
+    in_upper_level= TRUE;
+    cond_equal= cond_equal->upper_levels;
+  }
+  in_upper_level= FALSE;
+finish:
+  *inherited_fl= in_upper_level;
+  return item;
+}
+
+  
+/* 
+  Check whether an item is a simple equality predicate and if so
+  create/find a multiple equality for this predicate
+
+  SYNOPSIS
+    check_equality()
+    item       item to check
+    cond_equal multiple equalities that must hold together with the predicate
+
+  DESCRIPTION
+    This function first checks whether an item is a simple equality i.e.
+    the one that equates a field with another field or a constant
+    (item=constant_item or item=field_item).
+    If this is the case the function looks a for a multiple equality
+    in the lists referenced directly or indirectly by cond_equal inferring
+    the given simple equality. If it doesn't find any, it builds a multiple
+    equality that covers the predicate, i.e. the predicate can be inferred
+    from it.
+    The built multiple equality could be obtained in such a way:
+    create a binary  multiple equality equivalent to the predicate, then
+    merge it, if possible, with one of old multiple equalities.
+    This guarantees that the set of multiple equalities covering equality
+    predicates will
+    be minimal.
+
+  EXAMPLE
+    For the where condition
+    WHERE a=b AND b=c AND
+          (b=2 OR f=e)
+    the check_equality will be called for the following equality
+    predicates a=b, b=c, b=2 and f=e.
+    For a=b it will be called with *cond_equal=(0,[]) and will transform
+    *cond_equal into (0,[Item_equal(a,b)]). 
+    For b=c it will be called with *cond_equal=(0,[Item_equal(a,b)])
+    and will transform *cond_equal into CE=(0,[Item_equal(a,b,c)]).
+    For b=2 it will be called with *cond_equal=(ptr(CE),[])
+    and will transform *cond_equal into (ptr(CE,[Item_equal(2,a,b,c)]).
+    For f=e it will be called with *cond_equal=(ptr(CE), [])
+    and will transform *cond_equal into (ptr(CE,[Item_equal(f,e)]).
+
+  NOTES
+    Now only fields that have the same type defintions (verified by
+    the Field::eq_def method) are placed to the same multiple equalities.
+    Because of this some equality predicates are not eliminated and
+    can be used in the constant propagation procedure.
+    We could weeken the equlity test as soon as at least one of the 
+    equal fields is to be equal to a constant. It would require a 
+    more complicated implementation: we would have to store, in
+    general case, its own constant for each fields from the multiple
+    equality. But at the same time it would allow us to get rid
+    of constant propagation completely: it would be done by the call
+    to build_all_equal_items.
+    
+  IMPLEMENTATION
+    The implementation does not follow exactly the above rules to
+    build a new multiple equality for the equality predicate.
+    If it processes the equality of the form field1=field2, it
+    looks for multiple equalities me1 containig field1 and me2 containing
+    field2. If only one of them is found the fuction expands it with
+    the lacking field. If multiple equalities for both fields are
+    found they are merged. If both searches fail a new multiple equality
+    containing just field1 and field2 is added to the existing
+    multiple equalities.
+    If the function processes the predicate of the form field1=const,
+    it looks for a multiple equality containing field1. If found, the 
+    function checks the constant of the multiple equality. If the value
+    is unknown, it is setup to const. Otherwise the value is compared with
+    const and the evaluation of the equality predicate is performed.
+    When expanding/merging equality predicates from the upper levels
+    the function first copies them for the current level. It looks
+    acceptable, as this happens rarely. The implementation without
+    copying would be much more complicated.
+
+  RETURN
+    TRUE  - if the predicate is a simple equality predicate
+    FALSE - otherwise
+*/
+
+static bool check_equality(Item *item, COND_EQUAL *cond_equal)
+{
+  if (item->type() == Item::FUNC_ITEM &&
+         ((Item_func*) item)->functype() == Item_func::EQ_FUNC)
+  {
+    Item *left_item= ((Item_func*) item)->arguments()[0];
+    Item *right_item= ((Item_func*) item)->arguments()[1];
+    if (left_item->type() == Item::FIELD_ITEM &&
+        right_item->type() == Item::FIELD_ITEM)
+    {
+      /* The predicate the form field1=field2 is processed */
+
+      Field *left_field= ((Item_field*) left_item)->field;
+      Field *right_field= ((Item_field*) right_item)->field;
+
+      if (!left_field->eq_def(right_field))
+        return FALSE;
+
+      if (left_field->eq(right_field))  /* f = f */
+        return TRUE;
+      
+      /* Search for multiple equalities containing field1 and/or field2 */
+      bool left_copyfl, right_copyfl;
+      Item_equal *left_item_equal=
+                 find_item_equal(cond_equal, left_field, &left_copyfl);
+      Item_equal *right_item_equal= 
+                 find_item_equal(cond_equal, right_field, &right_copyfl);
+
+      if (left_item_equal && left_item_equal == right_item_equal)
+      {
+        /* 
+           The equality predicate is inference of one of the existing
+           multiple equalities, i.e the condition is already covered
+           by upper level equalities
+        */
+          return TRUE;
+      }
+      
+      /* Copy the found multiple equalities at the current level if needed */
+      if (left_copyfl)
+      {
+        /* left_item_equal of an upper level contains left_item */
+        left_item_equal= new Item_equal(left_item_equal);
+        cond_equal->current_level.push_back(left_item_equal);
+      }
+      if (right_copyfl)
+      {
+        /* right_item_equal of an upper level contains right_item */
+        right_item_equal= new Item_equal(right_item_equal);
+        cond_equal->current_level.push_back(right_item_equal);
+      }
+
+      if (left_item_equal)
+      { 
+        /* left item was found in the current or one of the upper levels */
+        if (! right_item_equal)
+          left_item_equal->add((Item_field *) right_item);
+        else
+        {
+          /* Merge two multiple equalities forming a new one */
+          left_item_equal->merge(right_item_equal);
+          /* Remove the merged multiple equality from the list */
+          List_iterator<Item_equal> li(cond_equal->current_level);
+          while ((li++) != right_item_equal);
+          li.remove();
+        }
+      }
+      else
+      { 
+        /* left item was not found neither the current nor in upper levels  */
+         if (right_item_equal)
+           right_item_equal->add((Item_field *) left_item);
+         else 
+         {
+           /* None of the fields was found in multiple equalities */
+           Item_equal *item= new Item_equal((Item_field *) left_item,
+                                            (Item_field *) right_item);
+           cond_equal->current_level.push_back(item);
+         }
+      }
+      return TRUE;
+    }
+
+    {
+      /* The predicate of the form field=const/const=field is processed */
+      Item *const_item= 0;
+      Item_field *field_item= 0;
+      if (left_item->type() == Item::FIELD_ITEM && 
+          right_item->const_item())
+      {
+        field_item= (Item_field*) left_item;
+        const_item= right_item;
+      }
+      else if (right_item->type() == Item::FIELD_ITEM && 
+               left_item->const_item())
+      {
+        field_item= (Item_field*) right_item;
+        const_item= left_item;
+      }
+      if (const_item &&
+          field_item->result_type() == const_item->result_type())
+      {
+        bool copyfl;
+
+        if (field_item->result_type() == STRING_RESULT &&
+              ((Field_str *) field_item)->charset() !=
+               ((Item_cond *) item)->compare_collation())
+          return FALSE;
+
+        Item_equal *item_equal = find_item_equal(cond_equal,
+                                                 field_item->field, &copyfl);
+        if (copyfl)
+        {
+          item_equal= new Item_equal(item_equal);
+          cond_equal->current_level.push_back(item_equal);
+        }
+        if (item_equal)
+        {
+          /* 
+            The flag cond_false will be set to 1 after this, if item_equal
+            already contains a constant and its value is  not equal to
+            the value of const_item.
+          */
+          item_equal->add(const_item);
+        }
+        else
+        {
+          item_equal= new Item_equal(const_item, field_item);
+          cond_equal->current_level.push_back(item_equal);
+        }
+        return TRUE;
+      }
+    }
+  }
+  return FALSE;
+}
+
+/* 
+  Replace all equality predicates in a condition by multiple equality items
+
+  SYNOPSIS
+    build_all_equal_items()
+    cond       condition(expression) where to make replacement
+    inherited  path to all inherited multiple equality items
+
+  DESCRIPTION
+    At each 'and' level the function detects items for equality predicates
+    and replaced them by a set of multiple equality items of class Item_equal,
+    taking into account inherited equalities from upper levels. 
+    If an equality predicate is used not in a conjunction it's just
+    replaced by a multiple equality predicate.
+    For each 'and' level the function set a pointer to the inherited
+    multiple equalities in the cond_equal field of the associated
+    object of the type Item_cond_and.   
+    The function also traverses the cond tree and and for each field reference
+    sets a pointer to the multiple equality item containing the field, if there
+    is any. If this multiple equality equates fields to a constant the
+    function replace the field reference by the constant.
+    The function also determines the maximum number of members in 
+    equality lists of each Item_cond_and object assigning it to
+    cond_equal->max_members of this object and updating accordingly
+    the upper levels COND_EQUAL structures.  
+
+  NOTES
+    Multiple equality predicate =(f1,..fn) is equivalent to the conjuction of
+    f1=f2, .., fn-1=fn. It substitutes any inference from these
+    equality predicates that is equivalent to the conjunction.
+    Thus, =(a1,a2,a3) can substitute for ((a1=a3) AND (a2=a3) AND (a2=a1)) as
+    it is equivalent to ((a1=a2) AND (a2=a3)).
+    The function always makes a substitution of all equality predicates occured
+    in a conjuction for a minimal set of multiple equality predicates.
+    This set can be considered as a canonical representation of the
+    sub-conjunction of the equality predicates.
+    E.g. (t1.a=t2.b AND t2.b>5 AND t1.a=t3.c) is replaced by 
+    (=(t1.a,t2.b,t3.c) AND t2.b>5), not by
+    (=(t1.a,t2.b) AND =(t1.a,t3.c) AND t2.b>5);
+    while (t1.a=t2.b AND t2.b>5 AND t3.c=t4.d) is replaced by
+    (=(t1.a,t2.b) AND =(t3.c=t4.d) AND t2.b>5),
+    but if additionally =(t4.d,t2.b) is inherited, it
+    will be replaced by (=(t1.a,t2.b,t3.c,t4.d) AND t2.b>5)
+
+  IMPLEMENTATION
+    The function performs the substitution in a recursive descent by
+    the condtion tree, passing to the next AND level a chain of multiple
+    equality predicates which have been built at the upper levels.
+    The Item_equal items built at the level are attached to other 
+    non-equality conjucts as a sublist. The pointer to the inherited
+    multiple equalities is saved in the and condition object (Item_cond_and).
+    This chain allows us for any field reference occurence easyly to find a 
+    multiple equality that must be held for this occurence.
+    For each AND level we do the following:
+    - scan it for all equality predicate (=) items
+    - join them into disjoint Item_equal() groups
+    - process the included OR conditions recursively to do the same for 
+      lower AND levels. 
+    We need to do things in this order as lower AND levels need to know about
+    all possible Item_equal objects in upper levels.
+
+  RETURN
+    pointer to the transformed condition
+*/
+
+static COND *build_all_equal_items(COND *cond,
+                                        COND_EQUAL *inherited)
+{
+  Item_equal *item_equal;
+  uint members;
+  COND_EQUAL cond_equal;
+  cond_equal.upper_levels= inherited;
+
+  if (cond->type() == Item::COND_ITEM)
+  {
+    bool and_level= ((Item_cond*) cond)->functype() ==
+      Item_func::COND_AND_FUNC;
+    List<Item> *args= ((Item_cond*) cond)->argument_list();
+    
+    List_iterator<Item> li(*args);
+    Item *item;
+
+    if (and_level)
+    {
+      /*
+         Retrieve all conjucts of this level detecting the equality
+         that are subject to substitution by multiple equality items and
+         removing each such predicate from the conjunction after having 
+         found/created a multiple equality whose inference the predicate is.
+     */      
+      while ((item= li++))
+      {
+        if (check_equality(item, &cond_equal))
+          li.remove();
+      }
+
+      List_iterator_fast<Item_equal> it(cond_equal.current_level);
+      while ((item_equal= it++))
+      {
+        item_equal->fix_length_and_dec();
+        item_equal->update_used_tables();
+        members= item_equal->members();
+        if (cond_equal.max_members < members)
+          cond_equal.max_members= members; 
+      }
+      members= cond_equal.max_members;
+      if (inherited && inherited->max_members < members)
+      {
+        do
+        {
+	  inherited->max_members= members;
+          inherited= inherited->upper_levels;
+        }
+        while (inherited);
+      }
+
+      ((Item_cond_and*)cond)->cond_equal= cond_equal;
+      inherited= &(((Item_cond_and*)cond)->cond_equal);
+    }
+    /*
+       Make replacement of equality predicates for lower levels
+       of the condition expression.
+    */
+    li.rewind();
+    while((item= li++))
+    { 
+      Item *new_item;
+      if ((new_item = build_all_equal_items(item, inherited))!= item)
+      {
+        /* This replacement happens only for standalone equalities */
+        li.replace(new_item);
+      }
+    }
+    if (and_level)
+      args->concat((List<Item> *)&cond_equal.current_level);
+  }
+  else if (cond->type() == Item::FUNC_ITEM)
+  {
+    /*
+      If an equality predicate forms the whole and level,
+      we call it standalone equality and it's processed here.
+      E.g. in the following where condition
+      WHERE a=5 AND (b=5 or a=c)
+      (b=5) and (a=c) are standalone equalities.
+      In general we can't leave alone standalone eqalities:
+      for WHERE a=b AND c=d AND (b=c OR d=5)
+      b=c is replaced by =(a,b,c,d).  
+     */
+    if (check_equality(cond, &cond_equal) &&
+        (item_equal= cond_equal.current_level.pop()))
+    {
+      item_equal->fix_length_and_dec();
+      item_equal->update_used_tables();
+      return item_equal;
+    }
+    /* 
+      For each field reference in cond, not from equalitym predicates,
+      set a pointer to the multiple equality if belongs to (if there is any)
+    */ 
+    cond= cond->transform(&Item::equal_fields_propagator,
+                            (byte *) inherited);
+    cond->update_used_tables();
+  }
+  return cond;
+}    
+
+/* 
+  Compare field items by table order in the execution plan
+ 
+  SYNOPSIS
+    compare_fields_by_table_order()
+    field1          first field item to compare
+    field2          second field item to compare
+    table_join_idx  index to tables determining table order    
+
+  DESCRIPTION
+    field1 considered as better than field2 if the table containing
+    field1 is accessed earlier than the table containing field2.   
+    The function finds out what of two fields is better according
+    this criteria.
+
+  RETURN
+     1, if field1 is better than field2 
+    -1, if field2 is better than field1
+     0, otherwise
+*/
+
+static int compare_fields_by_table_order(Item_field *field1,
+                                  Item_field *field2,
+                                  void *table_join_idx)
+{
+  int cmp= 0;
+  bool outer_ref= 0;
+  if (field2->used_tables() & OUTER_REF_TABLE_BIT)
+  {  
+    outer_ref= 1;
+    cmp= -1;
+  }
+  if (field2->used_tables() & OUTER_REF_TABLE_BIT)
+  {
+    outer_ref= 1;
+    cmp++;
+  }
+  if (outer_ref)
+    return cmp;
+  JOIN_TAB **idx= (JOIN_TAB **) table_join_idx;
+  cmp= idx[field2->field->table->tablenr]-idx[field1->field->table->tablenr];
+  return cmp < 0 ? -1 : (cmp ? 1 : 0);
+}
+
+
+/* 
+  Generate minimal set of simple equalities equivalent to a multiple equality
+ 
+  SYNOPSIS
+    eliminate_item_equal()
+    cond            condition to add the generated equality to
+    upper_levels    structure to access multiple equality of upper levels
+    item_equal      multiple equality to generate simple equality from     
+
+  DESCRIPTION
+    The function retrieves the fields of the multiple equality item
+    item_equal and  for each field f:
+    - if item_equal contains const it generates the equality f=const_item;
+    - otherwise, if f is not the first field, generates the equality
+      f=item_equal->get_first().
+    All generated equality are added to the cond conjunction.
+
+  NOTES
+    Before generating an equality function checks that it has not
+    been generated for multiple equalies of the upper levels.
+    E.g. for the following where condition
+    WHERE a=5 AND ((a=b AND b=c) OR  c>4)
+    the upper level AND condition will contain =(5,a),
+    while the lower level AND condition will contain =(5,a,b,c).
+    When splitting =(5,a,b,c) into a separate equality predicates
+    we should omit 5=a, as we have it already in the upper level.
+    The following where condition gives us a more complicated case:
+    WHERE t1.a=t2.b AND t3.c=t4.d AND (t2.b=t3.c OR t4.e>5 ...) AND ...
+    Given the tables are accessed in the order t1->t2->t3->t4 for
+    the selected query execution plan the lower level multiple
+    equality =(t1.a,t2.b,t3.c,t4.d) formally  should be converted to
+    t1.a=t2.b AND t1.a=t3.c AND t1.a=t4.d. But t1.a=t2.a will be
+    generated for the upper level. Also t3.c=t4.d will be generated there.
+    So only t1.a=t3.c should be left in the lower level.
+    If cond is equal to 0, then not more then one equality is generated
+    and a pointer to it is returned as the result of the function.
+
+  RETURN
+    The condition with generated simple equalities or
+    a pointer to the simple generated equality, if success.
+    0, otherwise.
+*/
+
+static Item *eliminate_item_equal(COND *cond, COND_EQUAL *upper_levels,
+                                  Item_equal *item_equal)
+{
+  List<Item> eq_list;
+  Item_func_eq *eq_item= 0;
+  Item *item_const= item_equal->get_const();
+  Item_equal_iterator it(*item_equal);
+  Item *head;
+  if (item_const)
+    head= item_const;
+  else
+  {
+    head= item_equal->get_first();
+    it++;
+  }
+  Item_field *item_field;
+  while ((item_field= it++))
+  {
+    Item_equal *upper= item_field->find_item_equal(upper_levels);
+    Item_field *item= item_field;
+    if (upper)
+    { 
+      if (item_const && upper->get_const())
+        item= 0;
+      else
+      {
+        Item_equal_iterator li(*item_equal);
+        while ((item= li++) != item_field)
+        {
+          if (item->find_item_equal(upper_levels) == upper)
+            break;
+        }
+      }
+    }
+    if (item == item_field)
+    {
+      if (eq_item)
+        eq_list.push_back(eq_item);
+      eq_item= new Item_func_eq(item_field, head);
+      if (!eq_item)
+        return 0;
+      eq_item->set_cmp_func();
+   }
+  }
+
+  if (!cond && !eq_list.head())
+    return eq_item;
+
+  eq_list.push_back(eq_item);
+  if (!cond)
+    cond= new Item_cond_and(eq_list);
+  else
+    ((Item_cond *) cond)->add_at_head(&eq_list);
+   
+  return cond;
+}
+
+
+/* 
+  Substitute every field reference in a condition by the best equal field 
+  and eliminate all multiplle equality predicates
+ 
+  SYNOPSIS
+    substitute_for_best_equal_field()
+    cond            condition to process
+    cond_equal      multiple equalities to take into consideration
+    table_join_idx  index to tables determining field preference
+
+  DESCRIPTION
+    The function retrieves the cond condition and for each encountered
+    multiple equality predicate it sorts the field references in it
+    according to the order of tables specified by the table_join_idx
+    parameter. Then it eliminates the multiple equality predicate it
+    replacing it by the conjunction of simple equality predicates 
+    equating every field from the multiple equality to the first
+    field in it, or to the constant, if there is any.
+    After this the function retrieves all other conjuncted
+    predicates substitute every field reference by the field reference
+    to the first equal field or equal constant if there are any.
+ 
+  NOTES
+    At the first glance full sort of fields in multiple equality
+    seems to be an overkill. Yet it's not the case due to possible
+    new fields in multiple equality item of lower levels. We want
+    the order in them to comply with the order of upper levels.
+
+  RETURN
+    The transformed condition
+*/
+
+static COND* substitute_for_best_equal_field(COND *cond,
+                                             COND_EQUAL *cond_equal,
+                                             void *table_join_idx)
+{
+  Item_equal *item_equal;
+
+  if (cond->type() == Item::COND_ITEM)
+  {
+    List<Item> *cond_list= ((Item_cond*) cond)->argument_list();
+
+    bool and_level= ((Item_cond*) cond)->functype() ==
+                      Item_func::COND_AND_FUNC;
+    if (and_level)
+    {
+      cond_equal= &((Item_cond_and *) cond)->cond_equal;
+      cond_list->disjoin((List<Item> *) &cond_equal->current_level);
+
+      List_iterator_fast<Item_equal> it(cond_equal->current_level);      
+      while ((item_equal= it++))
+      {
+        item_equal->sort(&compare_fields_by_table_order, table_join_idx);
+      }
+    }
+    
+    List_iterator<Item> li(*cond_list);
+    Item *item;
+    while ((item= li++))
+    {
+      Item *new_item =substitute_for_best_equal_field(item, cond_equal,
+                                                        table_join_idx);
+      if (new_item != item)
+        li.replace(new_item);
+   }
+
+    if (and_level)
+    {
+      List_iterator_fast<Item_equal> it(cond_equal->current_level);
+      while ((item_equal= it++))
+      {
+        eliminate_item_equal(cond, cond_equal->upper_levels, item_equal);
+      }
+    }
+  }
+  else if (cond->type() == Item::FUNC_ITEM && 
+           ((Item_cond*) cond)->functype() == Item_func::MULT_EQUAL_FUNC)
+  {
+    item_equal= (Item_equal *) cond;
+    item_equal->sort(&compare_fields_by_table_order, table_join_idx);
+    if (cond_equal && cond_equal->current_level.head() == item_equal)
+      cond_equal= 0;
+    return eliminate_item_equal(0, cond_equal, item_equal);
+  }
+  else
+    cond->walk(&Item::replace_equal_field_processor, 0);
+  return cond;
+}
+
+
 /*
   change field = field to field = const for each found field = const in the
   and_level
@@ -6164,15 +6997,13 @@ simplify_joins(JOIN *join, List<TABLE_LIST> *join_list, COND *conds, bool top)
       li.replace(nested_join->join_list);
     }
   }
-  DBUG_RETURN(conds);         
-}
-
-     
+  DBUG_RETURN(conds); 
+        
 static COND *
 optimize_cond(JOIN *join, COND *conds, Item::cond_result *cond_value)
 {
   THD *thd= join->thd;
-  SELECT_LEX *select= thd->lex->current_select;
+  SELECT_LEX *select= thd->lex->current_select;}    
   DBUG_ENTER("optimize_cond");
 
   if (select->first_cond_optimization)
@@ -6216,7 +7047,6 @@ optimize_cond(JOIN *join, COND *conds, Item::cond_result *cond_value)
     DBUG_EXECUTE("where",print_where(conds,"after const change"););
     conds= remove_eq_conds(thd, conds, cond_value) ;
     DBUG_EXECUTE("info",print_where(conds,"after remove"););
-  }
   DBUG_RETURN(conds);
 }
 
@@ -6340,6 +7170,11 @@ remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value)
 	}
       }
     }
+    if (cond->const_item())
+    {
+      *cond_value= eval_const_cond(cond) ? Item::COND_TRUE : Item::COND_FALSE;
+      return (COND*) 0;
+    }
   }
   else if (cond->const_item())
   {
@@ -9843,6 +10678,7 @@ join_init_cache(THD *thd,JOIN_TAB *tables,uint table_count)
   }
   if (!(cache->field=(CACHE_FIELD*)
 	sql_alloc(sizeof(CACHE_FIELD)*(cache->fields+table_count*2)+(blobs+1)*
+
 		  sizeof(CACHE_FIELD*))))
   {
     my_free((gptr) cache->buff,MYF(0));		/* purecov: inspected */

sql/sql_select.h

@@ -222,6 +222,7 @@ class JOIN :public Sql_alloc
   Item *conds_history;                    // store WHERE for explain
   TABLE_LIST *tables_list;           //hold 'tables' parameter of mysql_select
   List<TABLE_LIST> *join_list;       // list of joined tables in reverse order
+  COND_EQUAL *cond_equal;
   SQL_SELECT *select;                //created in optimisation phase
   JOIN_TAB *return_tab;              //used only for outer joins
   Item **ref_pointer_array; //used pointer reference for this select
@@ -284,6 +285,7 @@ class JOIN :public Sql_alloc
     ref_pointer_array_size= 0;
     zero_result_cause= 0;
     optimized= 0;
+    cond_equal= 0;
 
     fields_list= fields_arg;
     bzero((char*) &keyuse,sizeof(keyuse));