Many files:

  After review fixes for Item_equal.


sql/item.cc:
  After review fixes for Item_equal.
sql/item.h:
  After review fixes for Item_equal.
sql/item_cmpfunc.cc:
  After review fixes for Item_equal.
sql/item_cmpfunc.h:
  After review fixes for Item_equal.
sql/item_func.h:
  After review fixes for Item_equal.
sql/item_func.cc:
  After review fixes for Item_equal.
sql/item_row.cc:
  After review fixes for Item_equal.
sql/item_row.h:
  After review fixes for Item_equal.
sql/item_strfunc.h:
  After review fixes for Item_equal.
sql/opt_range.cc:
  After review fixes for Item_equal.
sql/sql_list.h:
  After review fixes for Item_equal.
sql/sql_select.cc:
  After review fixes for Item_equal.
mysql-test/r/select.result:
  After review fixes for Item_equal.
mysql-test/r/subselect.result:
  After review fixes for Item_equal.

mysql-test/r/select.result

@@ -1470,7 +1470,7 @@ explain extended select count(*),min(fld4),max(fld4),sum(fld1),avg(fld1),std(fld
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	1199	Using where
 Warnings:
-Note	1003	select high_priority count(0) AS `count(*)`,min(test.t2.fld4) AS `min(fld4)`,max(test.t2.fld4) AS `max(fld4)`,sum(test.t2.fld1) AS `sum(fld1)`,avg(test.t2.fld1) AS `avg(fld1)`,std(test.t2.fld1) AS `std(fld1)`,variance(test.t2.fld1) AS `variance(fld1)` from test.t2 where ((test.t2.fld4 <> _latin1'') and (test.t2.companynr = 34))
+Note	1003	select high_priority count(0) AS `count(*)`,min(test.t2.fld4) AS `min(fld4)`,max(test.t2.fld4) AS `max(fld4)`,sum(test.t2.fld1) AS `sum(fld1)`,avg(test.t2.fld1) AS `avg(fld1)`,std(test.t2.fld1) AS `std(fld1)`,variance(test.t2.fld1) AS `variance(fld1)` from test.t2 where ((test.t2.companynr = 34) and (test.t2.fld4 <> _latin1''))
 select companynr,count(*),min(fld4),max(fld4),sum(fld1),avg(fld1),std(fld1),variance(fld1) from t2 group by companynr limit 3;
 companynr	count(*)	min(fld4)	max(fld4)	sum(fld1)	avg(fld1)	std(fld1)	variance(fld1)
 00	82	Anthony	windmills	10355753	126289.6707	115550.9757	13352027981.7087

mysql-test/r/subselect.result

@@ -540,7 +540,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	const	PRIMARY,numreponse	PRIMARY	7	const,const	1	
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 Warnings:
-Note	1003	select high_priority test.t1.numreponse AS `numreponse` from test.t1 where ((test.t1.numeropost = _latin1'1') and (test.t1.numreponse = (select max(test.t1.numreponse) AS `MAX(numreponse)` from test.t1 where (test.t1.numeropost = _latin1'1'))))
+Note	1003	select high_priority test.t1.numreponse AS `numreponse` from test.t1 where ((test.t1.numreponse = (select max(test.t1.numreponse) AS `MAX(numreponse)` from test.t1 where (test.t1.numeropost = _latin1'1'))) and (test.t1.numeropost = _latin1'1'))
 drop table t1;
 CREATE TABLE t1 (a int(1));
 INSERT INTO t1 VALUES (1);
@@ -899,7 +899,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	DEPENDENT SUBQUERY	t2	ref_or_null	a	a	5	func	2	Using where; Using index
 2	DEPENDENT SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	3	Using where
 Warnings:
-Note	1003	select high_priority test.t1.a AS `a`,<in_optimizer>(test.t1.a,<exists>(select 1 AS `Not_used` from test.t2 join test.t3 where (((<cache>(test.t1.a) = test.t2.a) or isnull(test.t2.a)) and (test.t3.a = test.t2.a)) having <is_not_null_test>(test.t2.a) limit 1)) AS `t1.a in (select t2.a from t2,t3 where t3.a=t2.a)` from test.t1
+Note	1003	select high_priority test.t1.a AS `a`,<in_optimizer>(test.t1.a,<exists>(select 1 AS `Not_used` from test.t2 join test.t3 where ((test.t3.a = test.t2.a) and ((<cache>(test.t1.a) = test.t2.a) or isnull(test.t2.a))) having <is_not_null_test>(test.t2.a) limit 1)) AS `t1.a in (select t2.a from t2,t3 where t3.a=t2.a)` from test.t1
 drop table t1,t2,t3;
 create table t1 (a float);
 select 10.5 IN (SELECT * from t1 LIMIT 1);
@@ -1312,7 +1312,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	DEPENDENT SUBQUERY	t1	eq_ref	PRIMARY	PRIMARY	4	func	1	Using where
 2	DEPENDENT SUBQUERY	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.b	1	Using where; Using index
 Warnings:
-Note	1003	select high_priority test.t2.a AS `a` from test.t2 where <in_optimizer>(test.t2.a,<exists>(select 1 AS `Not_used` from test.t1 join test.t3 where ((<cache>(test.t2.a) = test.t1.a) and (test.t3.a = test.t1.b)) limit 1))
+Note	1003	select high_priority test.t2.a AS `a` from test.t2 where <in_optimizer>(test.t2.a,<exists>(select 1 AS `Not_used` from test.t1 join test.t3 where ((test.t3.a = test.t1.b) and (<cache>(test.t2.a) = test.t1.a)) limit 1))
 drop table t1, t2, t3;
 create table t1 (a int, b int, index a (a,b));
 create table t2 (a int, index a (a));
@@ -1351,7 +1351,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	DEPENDENT SUBQUERY	t1	ref	a	a	5	func	1001	Using where; Using index
 2	DEPENDENT SUBQUERY	t3	index	a	a	5	NULL	3	Using where; Using index
 Warnings:
-Note	1003	select high_priority test.t2.a AS `a` from test.t2 where <in_optimizer>(test.t2.a,<exists>(select 1 AS `Not_used` from test.t1 join test.t3 where ((<cache>(test.t2.a) = test.t1.a) and (test.t3.a = test.t1.b)) limit 1))
+Note	1003	select high_priority test.t2.a AS `a` from test.t2 where <in_optimizer>(test.t2.a,<exists>(select 1 AS `Not_used` from test.t1 join test.t3 where ((test.t3.a = test.t1.b) and (<cache>(test.t2.a) = test.t1.a)) limit 1))
 insert into t1 values (3,31);
 select * from t2 where t2.a in (select a from t1 where t1.b <> 30);
 a

sql/item.cc

@@ -994,6 +994,28 @@ bool Item_field::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
   return 0;
 }
 
+
+/*
+  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
+*/
+
 Item_equal *Item_field::find_item_equal(COND_EQUAL *cond_equal)
 {
   Item_equal *item= 0;
@@ -1005,31 +1027,82 @@ Item_equal *Item_field::find_item_equal(COND_EQUAL *cond_equal)
       if (item->contains(field))
         return item;
     }
-    cond_equal= cond_equal->parent_level;
+    /* 
+      The field is not found in any of the multiple equalities
+      of the current level. Look for it in upper levels
+    */
+    cond_equal= cond_equal->upper_levels;
   }
-  return item;
+  return 0;
 }
 
+
+/*
+  Set a pointer to the multiple equality the field reference belongs to (if any)
+   
+  SYNOPSIS
+    equal_fields_propagator()
+    arg - reference to list of multiple equalities where
+          the field (this object) is to be looked for
+  
+  DESCRIPTION
+    The function looks for a multiple equality containing the field item
+    among those referenced by arg.
+    In the case such equality exists the function does the following.
+    If the found multiple equality contains a constant, then the field
+    reference is substituted for this constant, otherwise it sets a pointer
+    to the multiple equality in the field item.
+
+  NOTES
+    This function is supposed to be called as a callback parameter in calls
+    of the transform method.  
+
+  RETURN VALUES
+    pointer to the replacing constant item, if the field item was substituted 
+    pointer to the field item, otherwise.
+*/
+
 Item *Item_field::equal_fields_propagator(byte *arg)
 {
-  COND_EQUAL *cond_equal= (COND_EQUAL *) arg;
-  item_equal= find_item_equal(cond_equal);
+  item_equal= find_item_equal((COND_EQUAL *) arg);
   Item *item= 0;
   if (item_equal)
     item= item_equal->get_const();
-  if (item)
-    item->fixed= 0;
-  else
+  if (!item)
     item= this;
   return item;
 }
 
+
+/*
+  Set a pointer to the multiple equality the field reference belongs to (if any)
+   
+  SYNOPSIS
+    replace_equal_field_processor()
+    arg - a dummy parameter, is not used here
+  
+  DESCRIPTION
+    The function replaces a pointer to a field in the Item_field object
+    by a pointer to another field.
+    The replacement field is taken from the very beginning of
+    the item_equal list which the Item_field object refers to (belongs to)  
+    If the Item_field object does not refer any Item_equal object,
+    nothing is done.
+
+  NOTES
+    This function is supposed to be called as a callback parameter in calls
+    of the walk method.  
+
+  RETURN VALUES
+    0 
+*/
+
 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))
+    if (!field->eq(subst->field))
     {
       field= subst->field;
       return 0;

sql/item.h

@@ -83,7 +83,7 @@ class DTCollation {
 };
 
 typedef bool (Item::*Item_processor)(byte *arg);
-typedef Item* (Item::*Item_calculator) (byte *arg);
+typedef Item* (Item::*Item_transformer) (byte *arg);
 
 class Item {
   Item(const Item &);			/* Prevent use of these */
@@ -212,9 +212,9 @@ class Item {
     return (this->*processor)(arg);
   }
 
-   virtual Item* traverse(Item_calculator calculator, byte *arg)
+   virtual Item* transform(Item_transformer transformer, byte *arg)
   {
-    return (this->*calculator)(arg);
+    return (this->*transformer)(arg);
   }
  
   virtual bool remove_dependence_processor(byte * arg) { return 0; }
@@ -949,13 +949,17 @@ class Item_default_value : public Item_field
       (this->*processor)(args);
   }
 
-  Item *traverse(Item_calculator calculator, byte *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->traverse(calculator, args);
+    Item *new_item= arg->transform(transformer, args);
     if (!new_item)
       return 0;
     arg= new_item;
-    return (this->*calculator)(args);
+    return (this->*transformer)(args);
   }
 };
 

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 && !args[0]->const_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 && !args[1]->const_item())
+  if (args[1]->type() == FIELD_ITEM /* && !args[1]->const_item() */)
   {
     Field *field=((Item_field*) args[1])->field;
     if (field->store_for_compare())
@@ -1739,21 +1739,44 @@ bool Item_cond::walk(Item_processor processor, byte *arg)
   return Item_func::walk(processor, arg);
 }
 
-Item *Item_cond::traverse(Item_calculator calculator, byte *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->traverse(calculator, arg);
+    Item *new_item= item->transform(transformer, arg);
     if (!new_item)
       return 0;
     if (new_item != item)
       li.replace(new_item);
   }
-  return Item_func::traverse(calculator, arg);
+  return Item_func::transform(transformer, arg);
 }
 
+
 void Item_cond::split_sum_func(Item **ref_pointer_array, List<Item> &fields)
 {
   List_iterator<Item> li(list);
@@ -2591,6 +2614,32 @@ 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);
@@ -2603,6 +2652,25 @@ bool Item_equal::contains(Field *field)
   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);
@@ -2619,26 +2687,46 @@ void Item_equal::merge(Item_equal *item)
   cond_false|= item->cond_false;
 } 
 
-void Item_equal::sort(void *table_join_idx)
+
+/*
+  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;
-  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 **ref2= it.ref();
+      if (cmp(item1, item2, arg) < 0)
       {
         Item_field *item= *ref1;
         *ref1= *ref2;
@@ -2680,6 +2768,8 @@ 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();
@@ -2697,7 +2787,7 @@ longlong Item_equal::val_int()
   if ((null_value= item->null_value))
     return 0;
   eval_item->store_value(item);
-  while((item= it++))
+  while ((item= it++))
   {
     if ((null_value= item->null_value) || eval_item->cmp(item))
       return 0;
@@ -2723,19 +2813,19 @@ bool Item_equal::walk(Item_processor processor, byte *arg)
   return Item_func::walk(processor, arg);
 }
 
-Item *Item_equal::traverse(Item_calculator calculator, byte *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->traverse(calculator, arg);
+    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::traverse(calculator, arg);
+  return Item_func::transform(transformer, arg);
 }
 
 void Item_equal::print(String *str)
@@ -2744,8 +2834,13 @@ void Item_equal::print(String *str)
   str->append('(');
   List_iterator_fast<Item_field> it(fields);
   Item *item;
-  if ((item= it++))
+  if (const_item)
+    const_item->print(str);
+  else
+  {
+    item= it++;
     item->print(str);
+  }
   while ((item= it++))
   {
     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;
@@ -890,6 +895,7 @@ class Item_cond :public Item_bool_func
     :Item_bool_func(), list(nlist), abort_on_null(0) {}
   ~Item_cond() { list.delete_elements(); }
   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; }
@@ -902,11 +908,75 @@ 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);
+  Item *transform(Item_transformer transformer, byte *arg);
   void neg_arguments();
 };
 
 
+/*
+  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                    */
@@ -924,7 +994,7 @@ class Item_equal: public Item_bool_func
   inline Item* get_const() { return const_item; }
   void add(Item *c);
   void add(Item_field *f);
-  bool is_false() { return cond_false; }
+  uint members();
   bool contains(Field *field);
   Item_field* get_first() { return fields.head(); }
   void merge(Item_equal *item);
@@ -932,22 +1002,29 @@ class Item_equal: public Item_bool_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);
+  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 *traverse(Item_calculator calculator, byte *arg);
+  Item *transform(Item_transformer transformer, byte *arg);
   void print(String *str);
 }; 
 
 class COND_EQUAL
 {
 public:
-  COND_EQUAL *parent_level;
-  List<Item_equal> current_level;
-  COND_EQUAL() { parent_level= 0; }
+  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;
+  }
 };
 
 
@@ -971,7 +1048,9 @@ class Item_equal_iterator :List_iterator_fast<Item_field>
 class Item_cond_and :public Item_cond
 {
 public:
-  COND_EQUAL cond_equal;  
+  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

@@ -242,37 +242,42 @@ bool Item_func::walk (Item_processor processor, byte *argument)
   return (this->*processor)(argument);
 }
 
-Item *Item_func::traverse(Item_calculator calculator, byte *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)->traverse(calculator, argument);
+      Item *new_item= (*arg)->transform(transformer, 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;
+  return (this->*transformer)(argument);
 }
 
 

sql/item_func.h

@@ -148,8 +148,7 @@ 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);
+  Item *transform(Item_transformer transformer, byte *arg);
 };
 
 

sql/item_row.cc

@@ -140,16 +140,16 @@ bool Item_row::walk(Item_processor processor, byte *arg)
   return (this->*processor)(arg);
 }
 
-Item *Item_row::traverse(Item_calculator calculator, byte *arg)
+Item *Item_row::transform(Item_transformer transformer, byte *arg)
 {
   for (uint i= 0; i < arg_count; i++)
   {
-    Item *new_item= items[i]->traverse(calculator, arg);
+    Item *new_item= items[i]->transform(transformer, arg);
     if (!new_item)
       return 0;
     items[i]= new_item;
   }
-  return (this->*calculator)(arg);
+  return (this->*transformer)(arg);
 }
 
 void Item_row::bring_value()

sql/item_row.h

@@ -71,7 +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);
+  Item *transform(Item_transformer transformer, byte *arg);
 
   uint cols() { return arg_count; }
   Item* el(uint i) { return items[i]; }

sql/item_strfunc.h

@@ -427,13 +427,13 @@ 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 *transform(Item_transformer transformer, byte *arg)
   {
-    Item *new_item= item->traverse(calculator, arg);
+    Item *new_item= item->transform(transformer, arg);
     if (!new_item)
       return 0;
     item= new_item;
-    return Item_str_func::traverse(calculator, arg);
+    return Item_str_func::transform(transformer, arg);
   }
   void print(String *str);
 };

sql/opt_range.cc

@@ -1494,6 +1494,21 @@ static int get_quick_select_params(SEL_TREE *tree, PARAM *param,
 }
 
 
+/*
+  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)
@@ -1501,9 +1516,8 @@ static SEL_TREE *get_func_mm_tree(PARAM *param, Item_func *cond_func,
   SEL_TREE *tree= 0;
   DBUG_ENTER("get_func_mm_tree");
 
-  if (cond_func->functype() == Item_func::NE_FUNC)
-  {
-  
+  switch (cond_func->functype()) {
+  case Item_func::NE_FUNC:
     tree= get_mm_parts(param, field, Item_func::LT_FUNC,
 		       value, cmp_type);
     if (tree)
@@ -1512,10 +1526,8 @@ static SEL_TREE *get_func_mm_tree(PARAM *param, Item_func *cond_func,
 					      Item_func::GT_FUNC,
 					      value, cmp_type));
     }
-  }
-  else if (cond_func->functype() == Item_func::BETWEEN)
-  {
-  
+    break;
+  case Item_func::BETWEEN:
     tree= get_mm_parts(param, field, Item_func::GE_FUNC,
 		       cond_func->arguments()[1],cmp_type);
     if (tree)
@@ -1525,30 +1537,42 @@ static SEL_TREE *get_func_mm_tree(PARAM *param, Item_func *cond_func,
 					       cond_func->arguments()[2],
                                                cmp_type));
     }
-  }
-  else if (cond_func->functype() == Item_func::IN_FUNC)
+    break;
+  case 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++)
+      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, field, 
                                                  Item_func::EQ_FUNC,
-                                                 func->arguments()[i],
+                                                 *arg,
                                                  cmp_type));
       }
     }
+    break;
   }
-  else 
+  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, field, func_type, value, cmp_type);
   }
+  }
+
   DBUG_RETURN(tree);
 
 }
@@ -1625,40 +1649,30 @@ 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
 
-  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;
-    }
-    else
-      DBUG_RETURN(0);
-  }
-  else if (cond_func->functype() == Item_func::IN_FUNC)
+    break;
+  case Item_func::IN_FUNC:
   {
     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;
   }
-    else
-      DBUG_RETURN(0);
-  }
-  else if (cond_func->functype() == Item_func::MULT_EQUAL_FUNC)
+  case 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)
-    {
+      DBUG_RETURN(0);
+    Item_equal_iterator it(*item_equal);
     ref_tables= value->used_tables();
-      Item_equal_iterator li(*item_equal);
-      while ((field_item= li++))
-      {
-        if (field_item != value)
+    while ((field_item= it++))
     {
       Field *field= field_item->field;
       Item_result cmp_type= field->cmp_type();
@@ -1669,14 +1683,11 @@ static SEL_TREE *get_mm_tree(PARAM *param,COND *cond)
         ftree= !ftree ? tree : tree_and(param, ftree, tree);
       }
     }
-      }
-      if (item_equal->get_const())
-        break;
-      value= it++;
-    }
+    
     DBUG_RETURN(ftree);
   }
-  else if (cond_func->arguments()[0]->type() == Item::FIELD_ITEM)
+  default:
+    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;
@@ -1689,6 +1700,19 @@ static SEL_TREE *get_mm_tree(PARAM *param,COND *cond)
     }
     else
       DBUG_RETURN(0);
+  }
+
+  /* 
+     If the where condition contains a predicate (ti.field op const),
+     then not only SELL_TREE for this predicate is built, but
+     the trees for the results of substitution of ti.field for
+     each tj.field belonging to the same multiple equality as ti.field
+     are built as well.
+     E.g. for WHERE t1.a=t2.a AND t2.a > 10 
+     a SEL_TREE for t2.a > 10 will be built for quick select from t2
+     and   
+     a SEL_TREE for t1.a > 10 will be built for quick select from t1.
+  */
      
   for (uint i= 0; i < cond_func->arg_count; i++)
   {

sql/sql_list.h

@@ -161,6 +161,15 @@ class base_list :public Sql_alloc
     *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; }
@@ -273,6 +282,7 @@ template <class T> class List :public base_list
   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;