This ChangeSet Introdices Item_equal.

The objects of this class represent multiple conjunctive equalities
in where conditions: =(f1,f2,...fn) <=> f1=f2 and f2= ... and =fn.
The objects are used to generate new possibale paths to access
the tables when executing a query.
They are also used to optimize the execution plan 
chosen by the optimizer for the query.  

sql/item.cc

@@ -299,7 +299,8 @@ bool DTCollation::aggregate(DTCollation &dt)
   return 0;
 }
 
-Item_field::Item_field(Field *f) :Item_ident(NullS,f->table_name,f->field_name)
+Item_field::Item_field(Field *f)
+  :Item_ident(NullS,f->table_name,f->field_name), item_equal(0)
 {
   set_field(f);
   collation.set(DERIVATION_IMPLICIT);
@@ -313,6 +314,7 @@ Item_field::Item_field(THD *thd, Item_field &item)
    result_field(item.result_field)
 {
   collation.set(DERIVATION_IMPLICIT);
+  item_equal= item.item_equal;
 }
 
 void Item_field::set_field(Field *field_par)
@@ -969,6 +971,49 @@ bool Item_field::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
   return 0;
 }
 
+Item_equal *Item_field::find_item_equal(COND_EQUAL *cond_equal)
+{
+  Item_equal *item= 0;
+  while (cond_equal)
+  {
+    List_iterator_fast<Item_equal> li(cond_equal->current_level);
+    while ((item= li++))
+    {
+      if (item->contains(field))
+        return item;
+    }
+    cond_equal= cond_equal->parent_level;
+  }
+  return item;
+}
+
+Item *Item_field::equal_fields_propagator(byte *arg)
+{
+  COND_EQUAL *cond_equal= (COND_EQUAL *) arg;
+  item_equal= find_item_equal(cond_equal);
+  Item *item= 0;
+  if (item_equal)
+    item= item_equal->get_const();
+  if (item)
+    item->fixed= 0;
+  else
+    item= this;
+  return item;
+}
+
+bool Item_field::replace_equal_field_processor(byte *arg)
+{
+  if (item_equal)
+  {
+    Item_field *subst= item_equal->get_first();
+    if (subst && !field->eq(subst->field))
+    {
+      field= subst->field;
+      return 0;
+    }
+  }
+  return 0;
+}
 
 void Item::init_make_field(Send_field *tmp_field,
 			   enum enum_field_types field_type)

sql/item.h

@@ -83,6 +83,7 @@ class DTCollation {
 };
 
 typedef bool (Item::*Item_processor)(byte *arg);
+typedef Item* (Item::*Item_calculator) (byte *arg);
 
 class Item {
   Item(const Item &);			/* Prevent use of these */
@@ -201,8 +202,15 @@ class Item {
     return (this->*processor)(arg);
   }
 
+   virtual Item* traverse(Item_calculator calculator, byte *arg)
+  {
+    return (this->*calculator)(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. */
@@ -311,17 +319,21 @@ class Item_ident :public Item
   bool remove_dependence_processor(byte * arg);
 };
 
+class Item_equal;
+class COND_EQUAL;
 
 class Item_field :public Item_ident
 {
   void set_field(Field *field);
 public:
   Field *field,*result_field;
+  Item_equal *item_equal;
   // Item_field() {}
 
   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)
+    :Item_ident(db_par,table_name_par,field_name_par),field(0),result_field(0),
+     item_equal(0)
   { collation.set(DERIVATION_IMPLICIT); }
   // Constructor need to process subselect with temporary tables (see Item)
   Item_field(THD *thd, Item_field &item);
@@ -355,6 +367,9 @@ class Item_field :public Item_ident
   bool get_time(TIME *ltime);
   bool is_null() { return field->is_null(); }
   Item *get_tmp_table_item(THD *thd);
+  Item_equal *find_item_equal(COND_EQUAL *cond_equal);
+  Item *equal_fields_propagator(byte *arg);
+  bool replace_equal_field_processor(byte *arg);
   friend class Item_default_value;
   friend class Item_insert_value;
 };
@@ -897,6 +912,15 @@ class Item_default_value : public Item_field
     return arg->walk(processor, args) ||
       (this->*processor)(args);
   }
+
+  Item *traverse(Item_calculator calculator, byte *args)
+  {
+    Item *new_item= arg->traverse(calculator, args);
+    if (!new_item)
+      return 0;
+    arg= new_item;
+    return (this->*calculator)(args);
+  }
 };
 
 class Item_insert_value : public Item_field

sql/item_cmpfunc.cc

@@ -225,7 +225,7 @@ void Item_bool_func2::fix_length_and_dec()
   }
   
   // Make a special case of compare with fields to get nicer DATE comparisons
-  if (args[0]->type() == FIELD_ITEM)
+  if (args[0]->type() == FIELD_ITEM && !args[0]->const_item())
   {
     Field *field=((Item_field*) args[0])->field;
     if (field->store_for_compare())
@@ -238,7 +238,7 @@ 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())
@@ -1712,6 +1712,21 @@ bool Item_cond::walk(Item_processor processor, byte *arg)
   return Item_func::walk(processor, arg);
 }
 
+Item *Item_cond::traverse(Item_calculator calculator, byte *arg)
+{
+  List_iterator<Item> li(list);
+  Item *item;
+  while ((item= li++))
+  {
+    Item *new_item= item->traverse(calculator, arg);
+    if (!new_item)
+      return 0;
+    if (new_item != item)
+      li.replace(new_item);
+  }
+  return Item_func::traverse(calculator, arg);
+}
+
 void Item_cond::split_sum_func(Item **ref_pointer_array, List<Item> &fields)
 {
   List_iterator<Item> li(list);
@@ -2499,3 +2514,217 @@ Item *Item_cond_or::neg_transformer()		/* NOT(a OR b OR ...)  -> */
   neg_arguments();
   return new Item_cond_and(list);
 }
+
+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);
+}
+
+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;
+}
+
+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;
+} 
+
+void Item_equal::sort(void *table_join_idx)
+{
+  bool swap;
+  void **idx= (void **) table_join_idx;
+  List_iterator<Item_field> it(fields);
+  do
+  {
+    Item_field *item1= it++;
+    Item_field **ref1= it.ref();
+    Item_field *item2;
+    Item_field **ref2;
+
+    if (!item1)
+      break; 
+    swap= FALSE;
+    while ((item2= it++))
+    {
+      ref2= it.ref();
+      if (idx[item1->field->table->tablenr] >
+          idx[item2->field->table->tablenr])
+      {
+        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;
+  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::traverse(Item_calculator calculator, byte *arg)
+{
+  List_iterator<Item_field> it(fields);
+  Item *item;
+  while ((item= it++))
+  {
+    Item *new_item= item->traverse(calculator, arg);
+    if (!new_item)
+      return 0;
+    if (new_item != item)
+      it.replace((Item_field *) new_item);
+  }
+  return Item_func::traverse(calculator, arg);
+}
+
+void Item_equal::print(String *str)
+{
+  str->append(func_name());
+  str->append('(');
+  List_iterator_fast<Item_field> it(fields);
+  Item *item;
+  if ((item= it++))
+    item->print(str);
+  while ((item= it++))
+  {
+    str->append(',');
+    str->append(' ');
+    item->print(str);
+  }
+  str->append(')');
+}
+

sql/item_cmpfunc.h

@@ -908,13 +908,76 @@ 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 *traverse(Item_calculator calculator, byte *arg);
   void neg_arguments();
 };
 
 
+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);
+  bool is_false() { return cond_false; }
+  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(void *table_join_idx);
+  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 *traverse(Item_calculator calculator, byte *arg);
+  void print(String *str);
+}; 
+
+class COND_EQUAL
+{
+public:
+  COND_EQUAL *parent_level;
+  List<Item_equal> current_level;
+  COND_EQUAL() { parent_level= 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;  
   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

@@ -242,6 +242,40 @@ bool Item_func::walk (Item_processor processor, byte *argument)
   return (this->*processor)(argument);
 }
 
+Item *Item_func::traverse(Item_calculator calculator, 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)->traverse(calculator, argument);
+      if (!new_item)
+	return 0;
+      *arg= new_item;
+    }
+  }
+  return (this->*calculator)(argument);
+}
+
+Item *Item_func::equal_fields_propagator(byte *argument)
+{
+  if (arg_count)
+  {
+    Item **arg,**arg_end;
+    for (arg= args, arg_end= args+arg_count; arg != arg_end; arg++)
+    {
+      if (!(*arg)->fixed)
+      {
+        fix_fields(current_thd, 0, 0);
+        break;
+      }
+    }
+  }
+  return this;
+}
+
+
 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,
@@ -49,7 +50,8 @@ class Item_func :public Item_result_field
 		  SP_POINTN,SP_GEOMETRYN,SP_INTERIORRINGN,
 		  NOT_FUNC, NOT_ALL_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):
@@ -146,6 +148,8 @@ class Item_func :public Item_result_field
   bool agg_arg_collations_for_comparison(DTCollation &c, Item **items, uint nitems);
 
   bool walk(Item_processor processor, byte *arg);
+  Item *traverse(Item_calculator calculator, byte *arg);
+  Item *equal_fields_propagator(byte *arg);
 };
 
 

sql/item_row.cc

@@ -140,6 +140,18 @@ bool Item_row::walk(Item_processor processor, byte *arg)
   return (this->*processor)(arg);
 }
 
+Item *Item_row::traverse(Item_calculator calculator, byte *arg)
+{
+  for (uint i= 0; i < arg_count; i++)
+  {
+    Item *new_item= items[i]->traverse(calculator, arg);
+    if (!new_item)
+      return 0;
+    items[i]= new_item;
+  }
+  return (this->*calculator)(arg);
+}
+
 void Item_row::bring_value()
 {
   for (uint i= 0; i < arg_count; i++)

sql/item_row.h

@@ -71,6 +71,7 @@ class Item_row: public Item
   void print(String *str);
 
   bool walk(Item_processor processor, byte *arg);
+  Item *traverse(Item_calculator calculator, byte *arg);
 
   uint cols() { return arg_count; }
   Item* el(uint i) { return items[i]; }

sql/item_strfunc.h

@@ -427,6 +427,14 @@ class Item_func_make_set :public Item_str_func
     return item->walk(processor, arg) ||
       Item_str_func::walk(processor, arg);
   }
+  Item *traverse(Item_calculator calculator, byte *arg)
+  {
+    Item *new_item= item->traverse(calculator, arg);
+    if (!new_item)
+      return 0;
+    item= new_item;
+    return Item_str_func::traverse(calculator, arg);
+  }
   void print(String *str);
 };
 

sql/opt_range.cc

@@ -762,11 +762,72 @@ int SQL_SELECT::test_quick_select(THD *thd, key_map keys_to_use,
   DBUG_RETURN(records ? test(quick) : -1);
 }
 
+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");
+
+  if (cond_func->functype() == Item_func::NE_FUNC)
+  {
+  
+    tree= get_mm_parts(param, field, Item_func::LT_FUNC,
+		       value, cmp_type);
+    if (tree)
+    {
+      tree= tree_or(param, tree, get_mm_parts(param, field,
+					       Item_func::GT_FUNC,
+					       value, cmp_type));
+    }
+  }
+  else if (cond_func->functype() == Item_func::BETWEEN)
+  {
+  
+    tree= get_mm_parts(param, field, Item_func::GE_FUNC,
+		       cond_func->arguments()[1],cmp_type);
+    if (tree)
+    {
+      tree= tree_and(param, tree, get_mm_parts(param, field,
+					       Item_func::LE_FUNC,
+					       cond_func->arguments()[2],
+                                               cmp_type));
+    }
+  }
+  else if (cond_func->functype() == Item_func::IN_FUNC)
+  {
+    Item_func_in *func=(Item_func_in*) cond_func;
+    tree= get_mm_parts(param, field, Item_func::EQ_FUNC,
+                       func->arguments()[1], cmp_type);
+    if (tree)
+    {
+      for (uint i =2 ; i < func->argument_count() ; i++)
+      {
+        tree=  tree_or(param, tree, get_mm_parts(param, field, 
+                                                 Item_func::EQ_FUNC,
+                                                 func->arguments()[i],
+                                                 cmp_type));
+      }
+    }
+  }
+  else 
+  {
+    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, 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)
@@ -814,9 +875,12 @@ 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);
@@ -828,76 +892,98 @@ static SEL_TREE *get_mm_tree(PARAM *param,COND *cond)
     DBUG_RETURN(0);				// Can't be calculated
 
   if (cond_func->functype() == Item_func::BETWEEN)
-  {
+  { 
     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, field,
-					Item_func::GE_FUNC,
-					cond_func->arguments()[1], cmp_type),
-			   get_mm_parts(param, field,
-					Item_func::LE_FUNC,
-					cond_func->arguments()[2], cmp_type)));
+      field_item= (Item_field*) (cond_func->arguments()[0]);
+      value= NULL;
     }
-    DBUG_RETURN(0);
+    else
+      DBUG_RETURN(0);
   }
-  if (cond_func->functype() == Item_func::IN_FUNC)
-  {						// COND OR
+  else if (cond_func->functype() == Item_func::IN_FUNC)
+  {
     Item_func_in *func=(Item_func_in*) cond_func;
     if (func->key_item()->type() == Item::FIELD_ITEM)
     {
-      Field *field=((Item_field*) (func->key_item()))->field;
-      Item_result cmp_type=field->cmp_type();
-      tree= get_mm_parts(param,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_item= (Item_field*) (func->key_item());
+      value= NULL;
+    }
+    else
+      DBUG_RETURN(0);
+  }
+  else if (cond_func->functype() == Item_func::MULT_EQUAL_FUNC)
+  {
+    Item_equal *item_equal= (Item_equal *) cond;    
+    Item_equal_iterator it(*item_equal);
+    if (!(value= item_equal->get_const()))
+      value= it++;
+    while (value)
+    {
+      ref_tables= value->used_tables();
+      Item_equal_iterator li(*item_equal);
+      while ((field_item= li++))
       {
-	SEL_TREE *new_tree=get_mm_parts(param,field,Item_func::EQ_FUNC,
-					func->arguments()[i],cmp_type);
-	tree=tree_or(param,tree,new_tree);
+        if (field_item != value)
+        {
+          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, 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,
-		       ((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,
-			     ((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()
-			     ));
+      if (item_equal->get_const())
+        break;
+      value= it++;
+    }
+    DBUG_RETURN(ftree);
   }
-  DBUG_RETURN(tree);
+  else if (cond_func->arguments()[0]->type() == Item::FIELD_ITEM)
+  {
+    field_item= (Item_field*) (cond_func->arguments()[0]);
+    value= cond_func->arg_count > 1 ? cond_func->arguments()[1] : 0;
+  }
+  else if (cond_func->have_rev_func() &&
+             cond_func->arguments()[1]->type() == Item::FIELD_ITEM)
+  {
+    field_item= (Item_field*) (cond_func->arguments()[1]);
+    value= cond_func->arguments()[0];
+  }
+  else
+    DBUG_RETURN(0);
+
+  for (uint i= 0; i < cond_func->arg_count; i++)
+  {
+    Item *arg= cond_func->arguments()[i];
+    if (arg != field_item)
+      ref_tables|= arg->used_tables();
+  }
+  Field *field= field_item->field;
+  Item_result cmp_type= field->cmp_type();
+  if (!((ref_tables | field->table->map) & param_comp))
+    ftree= get_func_mm_tree(param, cond_func, field, value, cmp_type);
+  Item_equal *item_equal= field_item->item_equal;
+  if (item_equal)
+  {
+    Item_equal_iterator it(*item_equal);
+    Item_field *item;
+    while ((item= it++))
+    {
+      Field *f= item->field;
+      if (field->eq(f))
+        continue;
+      if (!((ref_tables | f->table->map) & param_comp))
+      {
+        tree= get_func_mm_tree(param, cond_func, f, value, cmp_type);
+        ftree= !ftree ? tree : tree_and(param, ftree, tree);
+      }
+    }
+  }
+  DBUG_RETURN(ftree);
 }
 
 
@@ -905,17 +991,10 @@ static SEL_TREE *
 get_mm_parts(PARAM *param, 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;
@@ -951,13 +1030,6 @@ get_mm_parts(PARAM *param, Field *field, Item_func::Functype type,
     }
   }
 
-  if (ne_func)
-  {
-    SEL_TREE *tree2= get_mm_parts(param, field, Item_func::GT_FUNC,
-                                  value, cmp_type);
-    if (tree2)
-      tree= tree_or(param,tree,tree2);
-  }
   DBUG_RETURN(tree);
 }
 

sql/opt_sum.cc

@@ -352,6 +352,18 @@ 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];
@@ -492,6 +504,9 @@ 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

@@ -121,10 +121,12 @@ 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)
   {
@@ -135,6 +137,30 @@ class base_list :public Sql_alloc
       last= &first;
     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 list_node* last_node() { return *last; }
   inline list_node* first_node() { return first;}
   inline void *head() { return first->info; }
@@ -245,6 +271,8 @@ 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) { return base_list::concat(list); }
+  inline void disjoin(List<T> *list) { return base_list::disjoin(list); }
   void delete_elements(void)
   {
     list_node *element,*next;
@@ -265,6 +293,8 @@ 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

@@ -184,6 +184,7 @@ class JOIN :public Sql_alloc
   ORDER *order, *group_list, *proc_param; //hold parameters of mysql_select
   COND *conds;                            // ---"---
   Item *conds_history;                    // store WHERE for explain
+  COND_EQUAL *cond_equal;
   TABLE_LIST *tables_list;           //hold 'tables' parameter of mysql_selec
   SQL_SELECT *select;                //created in optimisation phase
   Item **ref_pointer_array; //used pointer reference for this select
@@ -243,6 +244,7 @@ class JOIN :public Sql_alloc
     ref_pointer_array_size= 0;
     zero_result_cause= 0;
     optimized= 0;
+    cond_equal= 0;
 
     fields_list= fields;
     bzero((char*) &keyuse,sizeof(keyuse));