MWL#17: Table elimination

Address review feedback: 
- Change from Wave-based approach (a-la const table detection) to 
  building and walking functional dependency graph.
- Change from piggy-backing on ref-access code and KEYUSE structures
  to using our own expression analyzer.


sql/item.cc:
  MWL#17: Table elimination
  - Move from C-ish Field_processor_info to C++ ish and generic Field_enumerator
sql/item.h:
  MWL#17: Table elimination
  - Move from C-ish Field_processor_info to C++ ish and generic Field_enumerator
sql/sql_bitmap.h:
  MWL#17: Table elimination
  - Backport of Table_map_iterator from 6.0

sql/item.cc

@@ -1918,30 +1918,8 @@ void Item_field::reset_field(Field *f)
 
 bool Item_field::check_column_usage_processor(uchar *arg)
 {
-  Field_processor_info* info=(Field_processor_info*)arg;
-
-  if (field->table == info->table)
-  {
-    /* It is not ok to use columns that are not part of the key of interest: */
-    if (!(field->part_of_key.is_set(info->keyno)))
-       return TRUE;
-
-    /* Find which key part we're using and mark it in needed_key_parts */
-    KEY *key= &field->table->key_info[info->keyno];
-    for (uint part= 0; part < key->key_parts; part++)
-    {
-      if (field->field_index == key->key_part[part].field->field_index)
-      {
-        if (part == info->forbidden_part)
-          return TRUE;
-        info->needed_key_parts |= key_part_map(1) << part;
-        break;
-      }
-    }
-    return FALSE;
-  }
-  else
-    info->used_tables |= this->used_tables();
+  Field_enumerator *fe= (Field_enumerator*)arg;
+  fe->see_field(field);
   return FALSE;
 }
 

sql/item.h

@@ -1017,7 +1017,7 @@ public:
   bool eq_by_collation(Item *item, bool binary_cmp, CHARSET_INFO *cs); 
 };
 
-/* Data for Item::check_column_usage_processor */
+#if 0
 typedef struct 
 {
   TABLE *table;         /* Table of interest */
@@ -1028,7 +1028,15 @@ typedef struct
   /* [Set by processor] Parts of index of interest that expression refers to */
   uint needed_key_parts;
 } Field_processor_info;
+#endif 
 
+/* Data for Item::check_column_usage_processor */
+class Field_enumerator
+{
+public:
+  virtual void see_field(Field *field)= 0;
+  virtual ~Field_enumerator() {}; /* Shut up compiler warning */
+};
 
 class sp_head;
 

sql/opt_table_elimination.cc

@@ -13,6 +13,7 @@
 #endif
 
 #include "mysql_priv.h"
+#include "my_bit.h"
 #include "sql_select.h"
 
 /*
@@ -35,137 +36,691 @@
   * Items that became disused because they were in the ON expression of an 
     eliminated outer join are notified by means of the Item tree walk which 
     calls Item::mark_as_eliminated_processor for every item
-    - At the moment the only Item that cares is Item_subselect with its 
-      Item_subselect::eliminated flag which is used by EXPLAIN code to
-      check if the subquery should be shown in EXPLAIN.
+    - At the moment the only Item that cares whether it was eliminated is 
+      Item_subselect with its Item_subselect::eliminated flag which is used
+      by EXPLAIN code to check if the subquery should be shown in EXPLAIN.
 
-  Table elimination is redone on every PS re-execution.
+  Table elimination is redone on every PS re-execution. (TODO reasons?)
 */
 
+/*
+  A structure that represents a functional dependency of something over
+  something else. This can be one of:
+
+  1. A "tbl.field = expr" equality. The field depends on the expression.
+  
+  2. An Item_equal(...) multi-equality. Each participating field depends on
+     every other participating field. (TODO???)
+  
+  3. A UNIQUE_KEY(field1, field2, fieldN). The key depends on the fields that
+     it is composed of.
+
+  4. A table (which is within an outer join nest). Table depends on a unique
+     key (value of a unique key identifies a table record)
+
+  5. An outer join nest. It depends on all tables it contains.
+
+*/
+
+class Func_dep : public Sql_alloc
+{
+public:
+  enum {
+    FD_INVALID,
+    FD_EXPRESSION,
+    FD_FIELD,
+    FD_MULTI_EQUALITY,
+    FD_UNIQUE_KEY,
+    FD_TABLE,
+    FD_OUTER_JOIN
+  } type;
+  Func_dep *next;
+  bool bound;
+  Func_dep() : next(NULL), bound(FALSE) {}
+};
+
+
+class Field_dep;
+class Table_dep;
+class Outer_join_dep;
+
+/*
+  An equality
+  - Depends on multiple fields (those in its expression), unknown_args is a 
+    counter of unsatisfied dependencies.
+*/
+class Equality_dep : public Func_dep
+{
+public:
+  Field_dep *field;
+  Item  *val;
+  
+  uint level; /* Used during condition analysis only */
+  uint unknown_args; /* Number of yet unknown arguments */
+};
+
+
+/*
+  A field.
+  - Depends on table or equality
+  - Has expressions it participates as dependencies
+
+  There is no counter, bound fields are in $list, not bound are not.
+*/
+class Field_dep : public Func_dep
+{
+public:
+  Field_dep(Table_dep *table_arg, Field *field_arg) :
+    table(table_arg), field(field_arg)
+  {
+    type= Func_dep::FD_FIELD;
+  }
+  /* Table we're from. It also has pointers to keys that we're part of */
+  Table_dep *table;
+  Field *field;
+  
+  Field_dep *next_table_field;
+  uint bitmap_offset; /* Offset of our part of the bitmap */
+};
+
+
+/*
+  A unique key.
+   - Depends on all its components
+   - Has its table as dependency
+*/
+class Key_dep: public Func_dep
+{
+public:
+  Key_dep(Table_dep *table_arg, uint keyno_arg, uint n_parts_arg) :
+    table(table_arg), keyno(keyno_arg), n_missing_keyparts(n_parts_arg),
+    next_table_key(NULL)
+  {
+    type= Func_dep::FD_UNIQUE_KEY;
+  }
+  Table_dep *table; /* Table this key is from */
+  uint keyno; // TODO do we care about this
+  uint n_missing_keyparts;
+  Key_dep *next_table_key;
+};
+
+
+/*
+  A table. 
+  - Depends on any of its unique keys
+  - Has its fields and embedding outer join as dependency.
+*/
+class Table_dep : public Func_dep
+{
+public:
+  Table_dep(TABLE *table_arg) : 
+    table(table_arg), fields(NULL), keys(NULL), outer_join_dep(NULL)
+  {
+    type= Func_dep::FD_TABLE;
+  }
+  TABLE *table;
+  Field_dep *fields; /* Fields that belong to this table */
+  Key_dep *keys; /* Unique keys */
+  Outer_join_dep *outer_join_dep;
+};
+
+
+/*
+  An outer join nest. 
+  - Depends on all tables inside it.
+  - (And that's it).
+*/
+class Outer_join_dep: public Func_dep
+{
+public:
+  Outer_join_dep(TABLE_LIST *table_list_arg, table_map missing_tables_arg) : 
+    table_list(table_list_arg), missing_tables(missing_tables_arg),
+    all_tables(missing_tables_arg), parent(NULL)
+  {
+    type= Func_dep::FD_OUTER_JOIN;
+  }
+  TABLE_LIST *table_list;
+  table_map missing_tables;
+  table_map all_tables;
+  Outer_join_dep *parent;
+};
+
+
+/* TODO need this? */
+class Table_elimination
+{
+public:
+  Table_elimination(JOIN *join_arg) : join(join_arg)
+  {
+    bzero(table_deps, sizeof(table_deps));
+  }
+
+  JOIN *join;
+  /* Array of equality dependencies */
+  Equality_dep *equality_deps;
+  uint n_equality_deps; /* Number of elements in the array */
+
+  /* tablenr -> Table_dep* mapping. */
+  Table_dep *table_deps[MAX_KEY];
+
+  /* Outer joins that are candidates for elimination */
+  List<Outer_join_dep> oj_deps;
+
+  /* Bitmap of how expressions depend on bits */
+  MY_BITMAP expr_deps;
+};
+
+
+static 
+void build_funcdeps_for_cond(Table_elimination *te, Equality_dep **fdeps, 
+                             uint *and_level, Item *cond, 
+                             table_map usable_tables);
+static 
+void add_funcdep(Table_elimination *te, 
+                 Equality_dep **eq_dep, uint and_level,
+                 Item_func *cond, Field *field,
+                 bool eq_func, Item **value,
+                 uint num_values, table_map usable_tables);
+static 
+Equality_dep *merge_func_deps(Equality_dep *start, Equality_dep *new_fields, 
+                              Equality_dep *end, uint and_level);
+
+Field_dep *get_field_dep(Table_elimination *te, Field *field);
+void eliminate_tables(JOIN *join);
 static void mark_as_eliminated(JOIN *join, TABLE_LIST *tbl);
-static bool table_has_one_match(TABLE *table, table_map bound_tables, 
-                                bool *multiple_matches);
-static uint
-eliminate_tables_for_list(JOIN *join, TABLE **leaves_arr,
-                          List<TABLE_LIST> *join_list,
-                          bool its_outer_join,
-                          table_map tables_in_list,
-                          table_map tables_used_elsewhere,
-                          bool *multiple_matches);
-static bool 
-extra_keyuses_bind_all_keyparts(table_map bound_tables, TABLE *table, 
-                                KEYUSE *key_start, KEYUSE *key_end, 
-                                uint n_keyuses, table_map bound_parts);
+
+#ifndef DBUG_OFF
+static void dbug_print_deps(Table_elimination *te);
+#endif 
+
+/*******************************************************************************************/
 
 /*
-  Perform table elimination
+  Produce FUNC_DEP elements for the given item (i.e. condition) and add them 
+    to fdeps array.
 
   SYNOPSIS
-    eliminate_tables()
-      join                   Join to work on
-      const_tbl_count INOUT  Number of constant tables (this includes
-                             eliminated tables)
-      const_tables    INOUT  Bitmap of constant tables
+    build_funcdeps_for_cond()
+      fdeps  INOUT   Put created FUNC_DEP structures here
 
   DESCRIPTION
-    This function is the entry point for table elimination. 
-    The idea behind table elimination is that if we have an outer join:
-   
-      SELECT * FROM t1 LEFT JOIN 
-        (t2 JOIN t3) ON t3.primary_key=t1.col AND 
-                        t4.primary_key=t2.col
-    such that
+    a
 
-    1. columns of the inner tables are not used anywhere ouside the outer
-       join (not in WHERE, not in GROUP/ORDER BY clause, not in select list 
-       etc etc), and
-    2. inner side of the outer join is guaranteed to produce at most one
-       record combination for each record combination of outer tables.
+  SEE ALSO
+    add_key_fields()
+
+*/
+static 
+void build_funcdeps_for_cond(Table_elimination *te, 
+                             Equality_dep **fdeps, uint *and_level, Item *cond,
+                             table_map usable_tables)
+{
+  if (cond->type() == Item_func::COND_ITEM)
+  {
+    List_iterator_fast<Item> li(*((Item_cond*) cond)->argument_list());
+    Equality_dep *org_key_fields= *fdeps;
     
-    then the inner side of the outer join can be removed from the query.
-    This is because it will always produce one matching record (either a
-    real match or a NULL-complemented record combination), and since there
-    are no references to columns of the inner tables anywhere, it doesn't
-    matter which record combination it was.
+    /* AND/OR */
+    if (((Item_cond*) cond)->functype() == Item_func::COND_AND_FUNC)
+    {
+      Item *item;
+      while ((item=li++))
+      {
+        build_funcdeps_for_cond(te, fdeps, and_level, item, usable_tables);
+      }
+      /* 
+        TODO: inject here a "if we have {t.col=const AND t.col=smth_else}, then
+        remove the second part" logic.
+      */
+      for (; org_key_fields != *fdeps ; org_key_fields++)
+        org_key_fields->level= *and_level;
+    }
+    else
+    {
+      (*and_level)++;
+      build_funcdeps_for_cond(te, fdeps, and_level, li++, usable_tables);
+      Item *item;
+      while ((item=li++))
+      {
+        Equality_dep *start_key_fields= *fdeps;
+        (*and_level)++;
+        build_funcdeps_for_cond(te, fdeps, and_level, item, usable_tables);
+        *fdeps= merge_func_deps(org_key_fields, start_key_fields, *fdeps,
+                                ++(*and_level));
+      }
+    }
+    return;
+  }
 
-    This function primary handles checking #1. It collects a bitmap of
-    tables that are not used in select list/GROUP BY/ORDER BY/HAVING/etc and
-    thus can possibly be eliminated.
-  
-  SIDE EFFECTS
-    See the OVERVIEW section at the top of this file.
+  if (cond->type() != Item::FUNC_ITEM)
+    return;
+  Item_func *cond_func= (Item_func*) cond;
+  switch (cond_func->select_optimize()) {
+  case Item_func::OPTIMIZE_NONE:
+    break;
+  case Item_func::OPTIMIZE_KEY:
+  {
+    Item **values;
+    // BETWEEN, IN, NE
+    if (cond_func->key_item()->real_item()->type() == Item::FIELD_ITEM &&
+       !(cond_func->used_tables() & OUTER_REF_TABLE_BIT))
+    {
+      values= cond_func->arguments()+1;
+      if (cond_func->functype() == Item_func::NE_FUNC &&
+          cond_func->arguments()[1]->real_item()->type() == Item::FIELD_ITEM &&
+         !(cond_func->arguments()[0]->used_tables() & OUTER_REF_TABLE_BIT))
+        values--;
+      DBUG_ASSERT(cond_func->functype() != Item_func::IN_FUNC ||
+                  cond_func->argument_count() != 2);
+      add_funcdep(te, fdeps, *and_level, cond_func,
+                  ((Item_field*)(cond_func->key_item()->real_item()))->field,
+                  0, values, 
+                  cond_func->argument_count()-1,
+                  usable_tables);
+    }
+    if (cond_func->functype() == Item_func::BETWEEN)
+    {
+      values= cond_func->arguments();
+      for (uint i= 1 ; i < cond_func->argument_count() ; i++)
+      {
+        Item_field *field_item;
+        if (cond_func->arguments()[i]->real_item()->type() == Item::FIELD_ITEM
+            &&
+            !(cond_func->arguments()[i]->used_tables() & OUTER_REF_TABLE_BIT))
+        {
+          field_item= (Item_field *) (cond_func->arguments()[i]->real_item());
+          add_funcdep(te, fdeps, *and_level, cond_func,
+                      field_item->field, 0, values, 1, usable_tables);
+        }
+      }  
+    }
+    break;
+  }
+  case Item_func::OPTIMIZE_OP:
+  {
+    bool equal_func=(cond_func->functype() == Item_func::EQ_FUNC ||
+                     cond_func->functype() == Item_func::EQUAL_FUNC);
 
-*/
+    if (cond_func->arguments()[0]->real_item()->type() == Item::FIELD_ITEM &&
+        !(cond_func->arguments()[0]->used_tables() & OUTER_REF_TABLE_BIT))
+    {
+      add_funcdep(te, fdeps, *and_level, cond_func,
+                  ((Item_field*)(cond_func->arguments()[0])->real_item())->field,
+                  equal_func,
+                  cond_func->arguments()+1, 1, usable_tables);
+    }
+    if (cond_func->arguments()[1]->real_item()->type() == Item::FIELD_ITEM &&
+        cond_func->functype() != Item_func::LIKE_FUNC &&
+        !(cond_func->arguments()[1]->used_tables() & OUTER_REF_TABLE_BIT))
+    {
+      add_funcdep(te, fdeps, *and_level, cond_func, 
+                  ((Item_field*)(cond_func->arguments()[1])->real_item())->field,
+                  equal_func,
+                  cond_func->arguments(),1,usable_tables);
+    }
+    break;
+  }
+  case Item_func::OPTIMIZE_NULL:
+    /* column_name IS [NOT] NULL */
+    if (cond_func->arguments()[0]->real_item()->type() == Item::FIELD_ITEM &&
+        !(cond_func->used_tables() & OUTER_REF_TABLE_BIT))
+    {
+      Item *tmp=new Item_null;
+      if (unlikely(!tmp))                       // Should never be true
+        return;
+      add_funcdep(te, fdeps, *and_level, cond_func,
+                  ((Item_field*)(cond_func->arguments()[0])->real_item())->field,
+                  cond_func->functype() == Item_func::ISNULL_FUNC,
+                  &tmp, 1, usable_tables);
+    }
+    break;
+  case Item_func::OPTIMIZE_EQUAL:
+    Item_equal *item_equal= (Item_equal *) cond;
+    Item *const_item= item_equal->get_const();
+    Item_equal_iterator it(*item_equal);
+    Item_field *item;
+    if (const_item)
+    {
+      /*
+        For each field field1 from item_equal consider the equality 
+        field1=const_item as a condition allowing an index access of the table
+        with field1 by the keys value of field1.
+      */   
+      while ((item= it++))
+      {
+        add_funcdep(te, fdeps, *and_level, cond_func, item->field,
+                    TRUE, &const_item, 1, usable_tables);
+      }
+    }
+    else 
+    {
+      /*
+        Consider all pairs of different fields included into item_equal.
+        For each of them (field1, field1) consider the equality 
+        field1=field2 as a condition allowing an index access of the table
+        with field1 by the keys value of field2.
+      */   
+      Item_equal_iterator fi(*item_equal);
+      while ((item= fi++))
+      {
+        Field *field= item->field;
+        while ((item= it++))
+        {
+          if (!field->eq(item->field))
+          {
+            add_funcdep(te, fdeps, *and_level, cond_func, field/*item*/,
+                        TRUE, (Item **) &item, 1, usable_tables);
+          }
+        }
+        it.rewind();
+      }
+    }
+    break;
+  }
+}
 
-void eliminate_tables(JOIN *join)
-{
-  Item *item;
-  table_map used_tables;
-  DBUG_ENTER("eliminate_tables");
+/*
+  Perform an OR operation on two (adjacent) FUNC_DEP arrays.
+
+  SYNOPSIS
+     merge_func_deps()
+
+  DESCRIPTION
+
+  This function is invoked for two adjacent arrays of FUNC_DEP elements:
+
+                      $LEFT_PART             $RIGHT_PART
+             +-----------------------+-----------------------+
+            start                new_fields                 end
+         
+  The goal is to produce an array which would correspnd to the combined 
   
-  DBUG_ASSERT(join->eliminated_tables == 0);
+    $LEFT_PART OR $RIGHT_PART
   
-  /* If there are no outer joins, we have nothing to eliminate: */
-  if (!join->outer_join)
-    DBUG_VOID_RETURN;
+  condition. This is achieved as follows: First, we apply distrubutive law:
+  
+    (fdep_A_1 AND fdep_A_2 AND ...)  OR  (fdep_B_1 AND fdep_B_2 AND ...) =
 
-  /* Find the tables that are referred to from WHERE/HAVING */
-  used_tables= (join->conds?  join->conds->used_tables() : 0) | 
-               (join->having? join->having->used_tables() : 0);
+     = AND_ij (fdep_A_[i] OR fdep_B_[j])
   
-  /* Add tables referred to from the select list */
-  List_iterator<Item> it(join->fields_list);
-  while ((item= it++))
-    used_tables |= item->used_tables();
- 
-  /* Add tables referred to from ORDER BY and GROUP BY lists */
-  ORDER *all_lists[]= { join->order, join->group_list};
-  for (int i=0; i < 2; i++)
+  Then we walk over the obtained "fdep_A_[i] OR fdep_B_[j]" pairs, and 
+   - Discard those that that have left and right part referring to different
+     columns. We can't infer anything useful from "col1=expr1 OR col2=expr2".
+   - When left and right parts refer to the same column,  we check if they are 
+     essentially the same. 
+     = If they are the same, we keep one copy 
+       "t.col=expr OR t.col=expr"  -> "t.col=expr 
+     = if they are different , then we discard both
+      "t.col=expr1 OR t.col=expr2" -> (nothing useful)
+
+  (no per-table or for-index FUNC_DEPS exist yet at this phase).
+
+  See also merge_key_fields().
+
+  RETURN 
+    End of the result array
+*/
+
+static 
+Equality_dep *merge_func_deps(Equality_dep *start, Equality_dep *new_fields, 
+                              Equality_dep *end, uint and_level)
+{
+  if (start == new_fields)
+    return start;				// Impossible or
+  if (new_fields == end)
+    return start;				// No new fields, skip all
+
+  Equality_dep *first_free=new_fields;
+
+  for (; new_fields != end ; new_fields++)
   {
-    for (ORDER *cur_list= all_lists[i]; cur_list; cur_list= cur_list->next)
-      used_tables |= (*(cur_list->item))->used_tables();
+    for (Equality_dep *old=start ; old != first_free ; old++)
+    {
+      /* 
+         TODO: does it make sense to attempt to merging multiple-equalities? 
+         A: YES.  
+           (a=b=c) OR (a=b=d)  produce "a=b". 
+         QQ: 
+           What to use for merging? Trivial N*M algorithm or pre-sort and then
+           merge ordered sequences?
+      */
+      if (old->field == new_fields->field)
+      {
+	if (!new_fields->val->const_item())
+	{
+	  /*
+	    If the value matches, we can use the key reference.
+	    If not, we keep it until we have examined all new values
+	  */
+	  if (old->val->eq(new_fields->val, old->field->field->binary()))
+	  {
+	    old->level= and_level;
+	  }
+	}
+	else if (old->val->eq_by_collation(new_fields->val, 
+                                           old->field->field->binary(),
+                                           old->field->field->charset()))
+	{
+	  old->level= and_level;
+	}
+	else
+	{
+          /* The expressions are different. */
+	  if (old == --first_free)		// If last item
+	    break;
+	  *old= *first_free;			// Remove old value
+	  old--;				// Retry this value
+	}
+      }
+    }
   }
-  
-  THD* thd= join->thd;
-  if (join->select_lex == &thd->lex->select_lex)
+
+  /* 
+    Ok, the results are within the [start, first_free) range, and the useful
+    elements have level==and_level. Now, lets remove all unusable elements:
+  */
+  for (Equality_dep *old=start ; old != first_free ;)
   {
-    /* Multi-table UPDATE and DELETE: don't eliminate the tables we modify: */
-    used_tables |= thd->table_map_for_update;
+    if (old->level != and_level)
+    {						// Not used in all levels
+      if (old == --first_free)
+	break;
+      *old= *first_free;			// Remove old value
+      continue;
+    }
+    old++;
+  }
+  return first_free;
+}
 
-    /* Multi-table UPDATE: don't eliminate tables referred from SET statement */
-    if (thd->lex->sql_command == SQLCOM_UPDATE_MULTI)
+
+/*
+  Add a funcdep for a given equality.
+*/
+
+static 
+void add_funcdep(Table_elimination *te, 
+                 Equality_dep **eq_dep, uint and_level,
+                 Item_func *cond, Field *field,
+                 bool eq_func, Item **value,
+                 uint num_values, table_map usable_tables)
+{
+ // Field *field= item_field->field;
+  if (!(field->table->map & usable_tables))
+    return;
+
+  for (uint i=0; i<num_values; i++)
+  {
+    if ((value[i])->used_tables() & RAND_TABLE_BIT)
+      return;
+  }
+
+  /*
+    Save the following cases:
+    Field op constant
+    Field LIKE constant where constant doesn't start with a wildcard
+    Field = field2 where field2 is in a different table
+    Field op formula
+    Field IS NULL
+    Field IS NOT NULL
+     Field BETWEEN ...
+     Field IN ...
+  */
+
+  /*
+    We can't always use indexes when comparing a string index to a
+    number. cmp_type() is checked to allow compare of dates to numbers.
+    eq_func is NEVER true when num_values > 1
+   */
+  if (!eq_func)
+  {
+    /* 
+      Additional optimization: if we're processing "t.key BETWEEN c1 AND c1"
+      then proceed as if we were processing "t.key = c1".
+    */
+    if ((cond->functype() != Item_func::BETWEEN) ||
+        ((Item_func_between*) cond)->negated ||
+        !value[0]->eq(value[1], field->binary()))
+      return;
+    eq_func= TRUE;
+  }
+
+  if (field->result_type() == STRING_RESULT)
+  {
+    if ((*value)->result_type() != STRING_RESULT)
     {
-      List_iterator<Item> it2(thd->lex->value_list);
-      while ((item= it2++))
-        used_tables |= item->used_tables();
+      if (field->cmp_type() != (*value)->result_type())
+        return;
+    }
+    else
+    {
+      /*
+        We can't use indexes if the effective collation
+        of the operation differ from the field collation.
+      */
+      if (field->cmp_type() == STRING_RESULT &&
+          ((Field_str*)field)->charset() != cond->compare_collation())
+        return;
+    }
+  }
+
+  DBUG_ASSERT(eq_func);
+  /* Store possible eq field */
+  (*eq_dep)->type=  Func_dep::FD_EXPRESSION; //psergey-todo;
+  (*eq_dep)->field= get_field_dep(te, field); 
+  (*eq_dep)->val=   *value;
+  (*eq_dep)->level= and_level;
+  (*eq_dep)++;
+}
+
+
+Table_dep *get_table_dep(Table_elimination *te, TABLE *table)
+{
+  Table_dep *tbl_dep= new Table_dep(table);
+  Key_dep **key_list= &(tbl_dep->keys);
+
+  /* Add dependencies for unique keys */
+  for (uint i=0; i < table->s->keys; i++)
+  {
+    KEY *key= table->key_info + i; 
+    if ((key->flags & (HA_NOSAME | HA_END_SPACE_KEY)) == HA_NOSAME)
+    {
+      Key_dep *key_dep= new Key_dep(tbl_dep, i, key->key_parts);
+      *key_list= key_dep;
+      key_list= &(key_dep->next_table_key);
     }
   }
+  return te->table_deps[table->tablenr] = tbl_dep;
+}
+
+/* 
+  Given a field, get its dependency element: if it already exists, find it,
+  otherwise create it.
+*/
+
+Field_dep *get_field_dep(Table_elimination *te, Field *field)
+{
+  TABLE *table= field->table;
+  Table_dep *tbl_dep;
+
+  if (!(tbl_dep= te->table_deps[table->tablenr]))
+    tbl_dep= get_table_dep(te, table);
+
+  Field_dep **pfield= &(tbl_dep->fields);
+  while (*pfield && (*pfield)->field->field_index < field->field_index)
+  {
+    pfield= &((*pfield)->next_table_field);
+  }
+  if (*pfield && (*pfield)->field->field_index == field->field_index)
+    return *pfield;
   
-  table_map all_tables= join->all_tables_map();
-  if (all_tables & ~used_tables)
+  Field_dep *new_field= new Field_dep(tbl_dep, field);
+  
+  new_field->next_table_field= *pfield;
+  *pfield= new_field;
+  return new_field;
+}
+
+
+Outer_join_dep *get_outer_join_dep(Table_elimination *te, 
+                                   TABLE_LIST *outer_join, table_map deps_map)
+{
+  Outer_join_dep *oj_dep;
+  oj_dep= new Outer_join_dep(outer_join, deps_map);
+
+  Table_map_iterator it(deps_map);
+  int idx;
+  while ((idx= it.next_bit()) != Table_map_iterator::BITMAP_END)
   {
-    /* There are some tables that we probably could eliminate. Try it. */
-    TABLE *leaves_array[MAX_TABLES];
-    bool multiple_matches= FALSE;
-    eliminate_tables_for_list(join, leaves_array, join->join_list, FALSE,
-                              all_tables, used_tables, &multiple_matches);
+    Table_dep *table_dep;
+    if (!(table_dep= te->table_deps[idx]))
+    {
+      TABLE *table= NULL;
+      /* 
+        Locate and create the table. The search isnt very efficient but 
+        typically we won't get here as we process the ON expression first
+        and that will create the Table_dep
+      */
+      for (uint i= 0; i < te->join->tables; i++)
+      {
+        if (te->join->join_tab[i].table->tablenr == (uint)idx)
+        {
+          table= te->join->join_tab[i].table;
+          break;
+        }
+      }
+      DBUG_ASSERT(table);
+      table_dep= get_table_dep(te, table);
+    }
+
+    if (!table_dep->outer_join_dep)
+      table_dep->outer_join_dep= oj_dep;
+    else
+    {
+      Outer_join_dep *oj= table_dep->outer_join_dep;
+      while (oj->parent)
+        oj= oj->parent;
+      oj->parent=oj_dep;
+    }
+
   }
-  DBUG_VOID_RETURN;
+  return oj_dep;
 }
 
+
 /*
   Perform table elimination in a given join list
 
   SYNOPSIS
-    eliminate_tables_for_list()
-      join                    The join
-      leaves_arr          OUT Store here an array of leaf (base) tables that 
-                              are descendants of the join_list, and increment 
-                              the pointer to point right above the array.
+    collect_funcdeps_for_join_list()
+      te                      Table elimination context.
       join_list               Join list to work on 
-      its_outer_join          TRUE <=> join_list is an inner side of an outer
-                                       join 
-                              FALSE <=> otherwise (this is top-level join list)
+      its_outer_join          TRUE <=> the join_list is an inner side of an 
+                                       outer join 
+                              FALSE <=> otherwise (this is top-level join 
+                                        list, simplify_joins flattens out all
+                                        other kinds of join lists)
+                                                    
       tables_in_list          Bitmap of tables embedded in the join_list.
       tables_used_elsewhere   Bitmap of tables that are referred to from
                               somewhere outside of the join list (e.g.
@@ -182,20 +737,18 @@ void eliminate_tables(JOIN *join)
     Number of children left after elimination. 0 means everything was
     eliminated.
 */
+
 static uint
-eliminate_tables_for_list(JOIN *join, TABLE **leaves_arr,
-                          List<TABLE_LIST> *join_list,
-                          bool its_outer_join,
-                          table_map tables_in_list,
-                          table_map tables_used_elsewhere,
-                          bool *multiple_matches)
+collect_funcdeps_for_join_list(Table_elimination *te,
+                               List<TABLE_LIST> *join_list,
+                               bool build_eq_deps,
+                               table_map tables_used_elsewhere,
+                               table_map *eliminable_tables,
+                               Equality_dep **eq_dep)
 {
   TABLE_LIST *tbl;
   List_iterator<TABLE_LIST> it(*join_list);
   table_map tables_used_on_left= 0;
-  TABLE **cur_table= leaves_arr;
-  bool children_have_multiple_matches= FALSE;
-  uint remaining_children= 0;
 
   while ((tbl= it++))
   {
@@ -203,253 +756,390 @@ eliminate_tables_for_list(JOIN *join, TABLE **leaves_arr,
     {
       table_map outside_used_tables= tables_used_elsewhere | 
                                      tables_used_on_left;
-      bool multiple_matches= FALSE;
+      bool eliminable;
+      table_map cur_map;
       if (tbl->nested_join)
       {
         /* This is  "... LEFT JOIN (join_nest) ON cond" */
-        uint n;
-        if (!(n= eliminate_tables_for_list(join, cur_table,
-                                           &tbl->nested_join->join_list, TRUE,
-                                           tbl->nested_join->used_tables, 
-                                           outside_used_tables, 
-                                           &multiple_matches)))
-        {
-          mark_as_eliminated(join, tbl);
-        }
-        else
-          remaining_children++;
-        tbl->nested_join->n_tables= n;
+        cur_map= tbl->nested_join->used_tables; 
+        eliminable= !(cur_map & outside_used_tables);
+        if (eliminable)
+          *eliminable_tables |= cur_map;
+        collect_funcdeps_for_join_list(te, &tbl->nested_join->join_list,
+                                       eliminable || build_eq_deps,
+                                       outside_used_tables,
+                                       eliminable_tables,
+                                       eq_dep);
       }
       else
       {
         /* This is  "... LEFT JOIN tbl ON cond" */
-        if (!(tbl->table->map & outside_used_tables) && 
-            table_has_one_match(tbl->table, join->all_tables_map(),
-                                &multiple_matches))
-        {
-          mark_as_eliminated(join, tbl);
-        }
-        else 
-          remaining_children++;
+        cur_map= tbl->table->map;
+        eliminable= !(tbl->table->map & outside_used_tables);
+        *eliminable_tables |= cur_map;
       }
-      tables_used_on_left |= tbl->on_expr->used_tables();
-      children_have_multiple_matches= children_have_multiple_matches ||  
-                                      multiple_matches;
-    }
-    else
-    {
-      DBUG_ASSERT(!tbl->nested_join);
-      remaining_children++;
-    }
-
-    if (tbl->table)
-      *(cur_table++)= tbl->table;
-  }
 
-  *multiple_matches |= children_have_multiple_matches;
-  
-  /* Try eliminating the nest we're called for */
-  if (its_outer_join && !children_have_multiple_matches &&
-      !(tables_in_list & tables_used_elsewhere))
-  {
-    table_map bound_tables= join->const_table_map | (join->all_tables_map() & 
-                                                     ~tables_in_list);
-    table_map old_bound_tables;
-    TABLE **leaves_end= cur_table;
-    /*
-      Do the same as const table search table: try to expand the set of bound 
-      tables until it covers all tables in the join_list
-    */
-    do
-    {
-      old_bound_tables= bound_tables;
-      for (cur_table= leaves_arr; cur_table != leaves_end; cur_table++)
+      if (eliminable || build_eq_deps)
       {
-        if (!((*cur_table)->map & join->eliminated_tables) && 
-            table_has_one_match(*cur_table, bound_tables, multiple_matches))
-        {
-          bound_tables |= (*cur_table)->map;
-        }
+        // build comp_cond from ON expression
+        uint and_level=0;
+        build_funcdeps_for_cond(te, eq_dep, &and_level, tbl->on_expr, 
+                                *eliminable_tables);
       }
-    } while (old_bound_tables != bound_tables);
-    
-    if (!(tables_in_list & ~bound_tables))
-    {
-      /* 
-        This join_list can be eliminated. Signal about this to the caller by
-        returning number of tables.
-      */
-      remaining_children= 0;
+
+      if (eliminable)
+        te->oj_deps.push_back(get_outer_join_dep(te, tbl, cur_map));
+
+      tables_used_on_left |= tbl->on_expr->used_tables();
     }
   }
-  return remaining_children;
+  return 0;
 }
 
-
 /*
-  Check if the table will produce at most one matching record
+  Analyze exising FUNC_DEP array and add elements for tables and uniq keys
 
   SYNOPSIS
-    table_has_one_match()
-      table                 The [base] table being checked 
-      bound_tables          Tables that should be considered bound.
-      multiple_matches OUT  Set to TRUE when there is no way we could 
-                            find find a limitation that would give us one-match
-                            property.
-
+  
   DESCRIPTION
-    Check if table will produce at most one matching record for each record 
-    combination of tables in bound_tables bitmap.
-
-    The check is based on ref analysis data, KEYUSE structures. We're
-    handling two cases:
-
-    1. Table has a UNIQUE KEY(uk_col_1, ... uk_col_N), and for each uk_col_i
-       there is a KEYUSE that represents a limitation in form
-
-         table.uk_col_i = func(bound_tables)                           (X)
+    Add FUNC_DEP elements
 
-    2. Same as above but we also handle limitations in form 
-
-         table.uk_col_i = func(bound_tables, uk_col_j1, ... uk_col_j2) (XX)
-
-       where values of uk_col_jN are known to be bound because for them we
-       have an equality of form (X) or (XX).
-
-  RETURN 
-    TRUE   Yes, at most one match
-    FALSE  No
+  RETURN
+    .
 */
 
-static bool table_has_one_match(TABLE *table, table_map bound_tables, 
-                                bool *multiple_matches)
+class Field_dependency_setter : public Field_enumerator
 {
-  KEYUSE *keyuse= table->reginfo.join_tab->keyuse;
-  if (keyuse)
+public:
+  Field_dependency_setter(Table_elimination *te_arg): te(te_arg)
+  {}
+  
+  void see_field(Field *field)
   {
-    while (keyuse->table == table)
+    Table_dep *tbl_dep;
+    if ((tbl_dep= te->table_deps[field->table->tablenr]))
     {
-      uint key= keyuse->key;
-      key_part_map bound_parts=0;
-      uint n_unusable=0;
-      bool ft_key= test(keyuse->keypart == FT_KEYPART);
-      KEY *keyinfo= table->key_info + key; 
-      KEYUSE *key_start = keyuse;
-      
-      do  /* For each keypart and each way to read it */
+      for (Field_dep *field_dep= tbl_dep->fields; field_dep; 
+           field_dep= field_dep->next_table_field)
       {
-        if (keyuse->type == KEYUSE_USABLE)
+        if (field->field_index == field_dep->field->field_index)
         {
-          if(!(keyuse->used_tables & ~bound_tables) &&
-             !(keyuse->optimize & KEY_OPTIMIZE_REF_OR_NULL))
-          {
-            bound_parts |= keyuse->keypart_map;
-          }
+          uint offs= field_dep->bitmap_offset + expr_offset;
+          if (!bitmap_is_set(&te->expr_deps, offs))
+            te->equality_deps[expr_offset].unknown_args++;
+          bitmap_set_bit(&te->expr_deps, offs);
+          return;
         }
-        else
-          n_unusable++;
-        keyuse++;
-      } while (keyuse->table == table && keyuse->key == key);
-      
-      if (ft_key || ((keyinfo->flags & (HA_NOSAME | HA_NULL_PART_KEY)) 
-                     != HA_NOSAME))
-      {
-        continue; 
       }
+      /* We didn't find the field. Bump the dependency anyway */
+      te->equality_deps[expr_offset].unknown_args++;
+    }
+  }
+  Table_elimination *te;
+  uint expr_offset; /* Offset of the expression we're processing */
+};
 
-      if (bound_parts == PREV_BITS(key_part_map, keyinfo->key_parts) ||
-          extra_keyuses_bind_all_keyparts(bound_tables, table, key_start,
-                                          keyuse, n_unusable, bound_parts))
+
+static 
+bool setup_equality_deps(Table_elimination *te, Func_dep **bound_deps_list)
+{
+  DBUG_ENTER("setup_equality_deps");
+  
+  uint offset= 0;
+  for (Table_dep **tbl_dep=te->table_deps; 
+       tbl_dep < te->table_deps + MAX_TABLES;
+       tbl_dep++)
+  {
+    if (*tbl_dep)
+    {
+      for (Field_dep *field_dep= (*tbl_dep)->fields;
+           field_dep;
+           field_dep= field_dep->next_table_field)
       {
-        return TRUE;
+        field_dep->bitmap_offset= offset;
+        offset += te->n_equality_deps;
       }
     }
   }
-  return FALSE;
+ 
+  void *buf;
+  if (!(buf= current_thd->alloc(bitmap_buffer_size(offset))) ||
+      bitmap_init(&te->expr_deps, (my_bitmap_map*)buf, offset, FALSE))
+  {
+    DBUG_RETURN(TRUE);
+  }
+  bitmap_clear_all(&te->expr_deps);
+
+  /* 
+    Walk through all field=expr elements and collect all fields.
+  */
+  Func_dep *bound_dep= NULL;
+  Field_dependency_setter deps_setter(te);
+  for (Equality_dep *eq_dep= te->equality_deps; 
+       eq_dep < te->equality_deps + te->n_equality_deps;
+       eq_dep++)
+  {
+    deps_setter.expr_offset= eq_dep - te->equality_deps;
+    eq_dep->unknown_args= 0;
+    eq_dep->val->walk(&Item::check_column_usage_processor, FALSE, 
+                      (uchar*)&deps_setter);
+    if (!eq_dep->unknown_args)
+    {
+      eq_dep->next= bound_dep;
+      bound_dep= eq_dep;
+      eq_dep->bound= TRUE;
+    }
+  }
+  *bound_deps_list= bound_dep;
+
+  DBUG_EXECUTE("test", dbug_print_deps(te); );
+  DBUG_RETURN(FALSE);
 }
 
 
 /*
-  Check if KEYUSE elemements with unusable==TRUE bind all parts of the key
+  Perform table elimination
 
   SYNOPSIS
-
-    extra_keyuses_bind_all_keyparts()
-      bound_tables   Tables which can be considered constants
-      table          Table we're examining
-      key_start      Start of KEYUSE array with elements describing the key
-                     of interest
-      key_end        End of the array + 1
-      n_keyuses      Number of elements in the array that have unusable==TRUE
-      bound_parts    Key parts whose values are known to be bound.
+    eliminate_tables()
+      join                   Join to work on
+      const_tbl_count INOUT  Number of constant tables (this includes
+                             eliminated tables)
+      const_tables    INOUT  Bitmap of constant tables
 
   DESCRIPTION
-    Check if unusable KEYUSE elements cause all parts of key to be bound. An 
-    unusable keyuse element makes a keypart bound when it
-    represents the following:
+    This function is the entry point for table elimination. 
+    The idea behind table elimination is that if we have an outer join:
+   
+      SELECT * FROM t1 LEFT JOIN 
+        (t2 JOIN t3) ON t3.primary_key=t1.col AND 
+                        t4.primary_key=t2.col
+    such that
 
-      keyXpartY=func(bound_columns, preceding_tables)
+    1. columns of the inner tables are not used anywhere ouside the outer
+       join (not in WHERE, not in GROUP/ORDER BY clause, not in select list 
+       etc etc), and
+    2. inner side of the outer join is guaranteed to produce at most one
+       record combination for each record combination of outer tables.
+    
+    then the inner side of the outer join can be removed from the query.
+    This is because it will always produce one matching record (either a
+    real match or a NULL-complemented record combination), and since there
+    are no references to columns of the inner tables anywhere, it doesn't
+    matter which record combination it was.
+
+    This function primary handles checking #1. It collects a bitmap of
+    tables that are not used in select list/GROUP BY/ORDER BY/HAVING/etc and
+    thus can possibly be eliminated.
+  
+  SIDE EFFECTS
+    See the OVERVIEW section at the top of this file.
 
-  RETURN 
-    TRUE   Yes, at most one match
-    FALSE  No
 */
 
-static bool 
-extra_keyuses_bind_all_keyparts(table_map bound_tables, TABLE *table, 
-                                KEYUSE *key_start, KEYUSE *key_end, 
-                                uint n_keyuses, table_map bound_parts)
+void eliminate_tables(JOIN *join)
 {
-  /*
-    We need 
-     - some 'unusable' KEYUSE elements to work on
-     - some keyparts to be already bound to start inferences: 
-  */
-  if (n_keyuses && bound_parts)
+  THD* thd= join->thd;
+  Item *item;
+  table_map used_tables;
+  DBUG_ENTER("eliminate_tables");
+  
+  DBUG_ASSERT(join->eliminated_tables == 0);
+
+  /* If there are no outer joins, we have nothing to eliminate: */
+  if (!join->outer_join)
+    DBUG_VOID_RETURN;
+
+  /* Find the tables that are referred to from WHERE/HAVING */
+  used_tables= (join->conds?  join->conds->used_tables() : 0) | 
+               (join->having? join->having->used_tables() : 0);
+  
+  /* Add tables referred to from the select list */
+  List_iterator<Item> it(join->fields_list);
+  while ((item= it++))
+    used_tables |= item->used_tables();
+ 
+  /* Add tables referred to from ORDER BY and GROUP BY lists */
+  ORDER *all_lists[]= { join->order, join->group_list};
+  for (int i=0; i < 2; i++)
   {
-    KEY *keyinfo= table->key_info + key_start->key;
-    bool bound_more_parts;
-    do 
+    for (ORDER *cur_list= all_lists[i]; cur_list; cur_list= cur_list->next)
+      used_tables |= (*(cur_list->item))->used_tables();
+  }
+  
+  if (join->select_lex == &thd->lex->select_lex)
+  {
+    /* Multi-table UPDATE and DELETE: don't eliminate the tables we modify: */
+    used_tables |= thd->table_map_for_update;
+
+    /* Multi-table UPDATE: don't eliminate tables referred from SET statement */
+    if (thd->lex->sql_command == SQLCOM_UPDATE_MULTI)
     {
-      bound_more_parts= FALSE;
-      for (KEYUSE *k= key_start; k!=key_end; k++)
+      List_iterator<Item> it2(thd->lex->value_list);
+      while ((item= it2++))
+        used_tables |= item->used_tables();
+    }
+  }
+  
+  table_map all_tables= join->all_tables_map();
+  if (all_tables & ~used_tables)
+  {
+    /* There are some tables that we probably could eliminate. Try it. */
+    Table_elimination te(join);
+    uint m= max(thd->lex->current_select->max_equal_elems,1);
+    uint max_elems= ((thd->lex->current_select->cond_count+1)*2 +
+                      thd->lex->current_select->between_count)*m + 1 + 10; 
+    if (!(te.equality_deps= new Equality_dep[max_elems]))
+      DBUG_VOID_RETURN;
+    Equality_dep *eq_deps_end= te.equality_deps;
+    table_map eliminable_tables= 0;
+    collect_funcdeps_for_join_list(&te, join->join_list,
+                                   FALSE,
+                                   used_tables,
+                                   &eliminable_tables,
+                                   &eq_deps_end);
+    te.n_equality_deps= eq_deps_end - te.equality_deps;
+    Func_dep *bound_dep;
+    setup_equality_deps(&te, &bound_dep);
+
+    /* 
+      Run the wave.
+      All Func_dep-derived objects are divided into three classes:
+      - Those that have bound=FALSE
+      - Those that have bound=TRUE 
+      - Those that have bound=TRUE and are in the list..
+
+    */
+    while (bound_dep)
+    {
+      Func_dep *next= bound_dep->next;
+      //e= list.remove_first();
+      switch (bound_dep->type)
       {
-        if (k->type == KEYUSE_UNKNOWN)
+        case Func_dep::FD_EXPRESSION:
         {
-          Field_processor_info fp= {table, k->key, k->keypart, 0, 0};
-          if (k->val->walk(&Item::check_column_usage_processor, FALSE, 
-                            (uchar*)&fp))
-            k->type= KEYUSE_NO_BIND;
-          else
+          /*  It's a field=expr and we got to know the expr, so we know the field */
+          Equality_dep *eq_dep= (Equality_dep*)bound_dep;
+          if (!eq_dep->field->bound)
           {
-            k->used_tables= fp.used_tables;
-            k->keypart_map= fp.needed_key_parts;
-            k->type= KEYUSE_BIND;
+            /* Mark as bound and add to the list */
+            eq_dep->field->bound= TRUE;
+            eq_dep->field->next= next;
+            next= eq_dep->field;
           }
+          break;
         }
-        
-        if (k->type == KEYUSE_BIND)
+        case Func_dep::FD_FIELD:
         {
           /*
-            If this is a binding keyuse, such that
-             - all tables it refers to are bound,
-             - all parts it refers to are bound
-             - but the key part it binds is not itself bound
+            Field became known. Check out
+            - unique keys we belong to
+            - expressions that depend on us.
           */
-          if (!(k->used_tables & ~bound_tables) && 
-              !(k->keypart_map & ~bound_parts) && 
-              !(bound_parts & key_part_map(1) << k->keypart))
+          Field_dep *field_dep= (Field_dep*)bound_dep;
+          for (Key_dep *key_dep= field_dep->table->keys; key_dep;
+               key_dep= key_dep->next_table_key)
+          {
+            DBUG_PRINT("info", ("key %s.%s is now bound",
+                                key_dep->table->table->alias, 
+                                key_dep->table->table->key_info[key_dep->keyno].name));
+            if (!key_dep->bound)
+            {
+              if (!--key_dep->n_missing_keyparts)
+              {
+                /* Mark as bound and add to the list */
+                key_dep->bound= TRUE;
+                key_dep->next= next;
+                next= key_dep;
+              }
+            }
+          }
+
+          /* Now, expressions */
+          for (uint i=0; i < te.n_equality_deps; i++)
           {
-            bound_parts|= key_part_map(1) << k->keypart;
-            if (bound_parts == PREV_BITS(key_part_map, keyinfo->key_parts))
-              return TRUE;
-            bound_more_parts= TRUE;
+            if (bitmap_is_set(&te.expr_deps, field_dep->bitmap_offset + i))
+            {
+              Equality_dep* eq_dep= &te.equality_deps[i];
+              if (!--eq_dep->unknown_args)
+              {
+                /* Mark as bound and add to the list */
+                eq_dep->bound= TRUE;
+                eq_dep->next= next;
+                next= eq_dep;
+              }
+            }
           }
+          break;
         }
+        case Func_dep::FD_UNIQUE_KEY:
+        {
+          /* Unique key is known means the table is known */
+          Table_dep *table_dep=((Key_dep*)bound_dep)->table;
+          if (!table_dep->bound)
+          {
+            /* Mark as bound and add to the list */
+            table_dep->bound= TRUE;
+            table_dep->next= next;
+            next= table_dep;
+          }
+          break;
+        }
+        case Func_dep::FD_TABLE:
+        {
+          Table_dep *table_dep=(Table_dep*)bound_dep; 
+          DBUG_PRINT("info", ("table %s is now bound",
+                              table_dep->table->alias));
+          /*
+            Table is known means
+            - all its fields are known
+            - one more element in outer join nest is known
+          */
+          for (Field_dep *field_dep= table_dep->fields; field_dep; 
+               field_dep= field_dep->next_table_field)
+          {
+            if (!field_dep->bound)
+            {
+              /* Mark as bound and add to the list */
+              field_dep->bound= TRUE;
+              field_dep->next= next;
+              next= field_dep;
+            }
+          }
+          Outer_join_dep *outer_join_dep= table_dep->outer_join_dep;
+          if (!(outer_join_dep->missing_tables &= ~table_dep->table->map))
+          {
+            /* Mark as bound and add to the list */
+            outer_join_dep->bound= TRUE;
+            outer_join_dep->next= next;
+            next= outer_join_dep;
+          }
+          break;
+        }
+        case Func_dep::FD_OUTER_JOIN:
+        {
+          Outer_join_dep *outer_join_dep= (Outer_join_dep*)bound_dep;
+          /* TODO what do here? Stop if eliminated the top-level? */
+          mark_as_eliminated(te.join, outer_join_dep->table_list);
+          Outer_join_dep *parent= outer_join_dep->parent;
+          if (parent && 
+              !(parent->missing_tables &= ~outer_join_dep->all_tables))
+          {
+            /* Mark as bound and add to the list */
+            parent->bound= TRUE;
+            parent->next= next;
+            next= parent;
+          }
+          break;
+        }
+        case Func_dep::FD_MULTI_EQUALITY:
+        default:
+          DBUG_ASSERT(0);
       }
-    } while (bound_more_parts);
+      bound_dep= next;
+    }
   }
-  return FALSE;
+  DBUG_VOID_RETURN;
 }
 
 
@@ -488,6 +1178,96 @@ static void mark_as_eliminated(JOIN *join, TABLE_LIST *tbl)
     tbl->on_expr->walk(&Item::mark_as_eliminated_processor, FALSE, NULL);
 }
 
+
+
+#ifndef DBUG_OFF
+static 
+void dbug_print_deps(Table_elimination *te)
+{
+  DBUG_ENTER("dbug_print_deps");
+  DBUG_LOCK_FILE;
+  
+  fprintf(DBUG_FILE,"deps {\n");
+  
+  /* Start with printing equalities */
+  for (Equality_dep *eq_dep= te->equality_deps; 
+       eq_dep != te->equality_deps + te->n_equality_deps; eq_dep++)
+  {
+    char buf[128];
+    String str(buf, sizeof(buf), &my_charset_bin);
+    str.length(0);
+    eq_dep->val->print(&str, QT_ORDINARY);
+    fprintf(DBUG_FILE, "  equality%d: %s -> %s.%s\n", 
+            eq_dep - te->equality_deps,
+            str.c_ptr(),
+            eq_dep->field->table->table->alias,
+            eq_dep->field->field->field_name);
+  }
+  fprintf(DBUG_FILE,"\n");
+
+  /* Then tables and their fields */
+  for (uint i=0; i < MAX_TABLES; i++)
+  {
+    Table_dep *table_dep;
+    if ((table_dep= te->table_deps[i]))
+    {
+      /* Print table */
+      fprintf(DBUG_FILE, "  table %s\n", table_dep->table->alias);
+      /* Print fields */
+      for (Field_dep *field_dep= table_dep->fields; field_dep; 
+           field_dep= field_dep->next_table_field)
+      {
+        fprintf(DBUG_FILE, "    field %s.%s ->", table_dep->table->alias,
+                field_dep->field->field_name);
+        uint ofs= field_dep->bitmap_offset;
+        for (uint bit= ofs; bit < ofs + te->n_equality_deps; bit++)
+        {
+          if (bitmap_is_set(&te->expr_deps, bit))
+            fprintf(DBUG_FILE, " equality%d ", bit - ofs);
+        }
+        fprintf(DBUG_FILE, "\n");
+      }
+    }
+  }
+  fprintf(DBUG_FILE,"\n}\n");
+  DBUG_UNLOCK_FILE;
+  DBUG_VOID_RETURN;
+}
+
+#endif 
+
+/***********************************************************************************************/
+
+#if 0
+static void dbug_print_fdep(FUNC_DEP *fd)
+{
+  switch (fd->type) {
+  case FUNC_DEP::FD_OUTER_JOIN:
+  {
+    fprintf(DBUG_FILE, "outer_join(");
+    if (fd->table_list->nested_join)
+    {
+      bool first= TRUE;
+      List_iterator<TABLE_LIST> it(fd->table_list->nested_join->join_list);
+      TABLE_LIST *tbl;
+      while ((tbl= it++))
+      {
+        fprintf(DBUG_FILE, "%s%s", first?"":" ", 
+                tbl->table? tbl->table->alias : "...");
+        first= FALSE;
+      }
+      fprintf(DBUG_FILE, ")");
+    }
+    else
+      fprintf(DBUG_FILE, "%s", fd->table_list->table->alias);
+    fprintf(DBUG_FILE, ")");
+    break;
+  }
+  }
+}
+
+#endif
+
 /**
   @} (end of group Table_Elimination)
 */

sql/sql_bitmap.h

@@ -93,6 +93,34 @@ public:
   }
 };
 
+/* An iterator to quickly walk over bits in unlonglong bitmap. */
+class Table_map_iterator
+{
+  ulonglong bmp;
+  uint no;
+public:
+  Table_map_iterator(ulonglong t) : bmp(t), no(0) {}
+  int next_bit()
+  {
+    static const char last_bit[16]= {32, 0, 1, 0, 
+                                      2, 0, 1, 0, 
+                                      3, 0, 1, 0,
+                                      2, 0, 1, 0};
+    uint bit;
+    while ((bit= last_bit[bmp & 0xF]) == 32)
+    {
+      no += 4;
+      bmp= bmp >> 4;
+      if (!bmp)
+        return BITMAP_END;
+    }
+    bmp &= ~(1LL << bit);
+    return no + bit;
+  }
+  int operator++(int) { return next_bit(); }
+  enum { BITMAP_END= 64 };
+};
+
 template <> class Bitmap<64>
 {
   ulonglong map;
@@ -136,5 +164,10 @@ public:
   my_bool operator==(const Bitmap<64>& map2) const { return map == map2.map; }
   char *print(char *buf) const { longlong2str(map,buf,16); return buf; }
   ulonglong to_ulonglong() const { return map; }
+  class Iterator : public Table_map_iterator
+  {
+  public:
+    Iterator(Bitmap<64> &bmp) : Table_map_iterator(bmp.map) {}
+  };
 };