Merge for Item_equal.

.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)
-  {
-    if (cond_func->arguments()[0]->type() == Item::FIELD_ITEM)
+  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:
   {
-      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)));
-    }
+    Item_func_in *func=(Item_func_in*) cond_func;
+    if (func->key_item()->type() != Item::FIELD_ITEM)
       DBUG_RETURN(0);
+    field_item= (Item_field*) (func->key_item());
+    value= NULL;
+    break;
   }
-  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)
+  case Item_func::MULT_EQUAL_FUNC:
   {
-      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++)
+    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++))
     {
-	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);
-      }
-      DBUG_RETURN(tree);
+      Field *field= field_item->field;
+      Item_result cmp_type= field->cmp_type();
+      if (!((ref_tables | field->table->map) & param_comp))
+      {
+        tree= get_mm_parts(param, cond, field, Item_func::EQ_FUNC,
+		           value,cmp_type);
+        ftree= !ftree ? tree : tree_and(param, ftree, 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)
   {
@@ -142,11 +144,38 @@ class base_list :public Sql_alloc
     return tmp->info;
   }
   inline void concat(base_list *list)
+  {
+    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;}
   inline void *head() { return first->info; }
@@ -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.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));