Fixed bug #16504.

Multiple equalities were not adjusted after reading constant tables.
It resulted in neglecting good index based methods that could be
used to access of other tables.


mysql-test/r/having.result:
  Adjusted a test case results after fix for bug #16504.
mysql-test/r/select.result:
  Added a test case for bug #16504.
mysql-test/r/subselect.result:
  Adjusted a test case results after fix for bug #16504.
mysql-test/r/varbinary.result:
  Adjusted a test case results after fix for bug #16504.
mysql-test/t/select.test:
  Added a test case for bug #16504.
sql/item.cc:
  Fixed bug #16504.
  An Item_equal object may contain only a constant member.
  It may happen after reading constant tables.
sql/item_cmpfunc.cc:
  Fixed bug #16504.
  Added method Item_equal::check_const that check appearance of new 
  constant items in a multiple equality.
sql/item_cmpfunc.h:
  Fixed bug #16504.
  Added method Item_equal::check_const that check appearance of new 
  constant items in a multiple equality.
sql/sql_select.cc:
  Fixed bug #16504.
  Adjusted multiple equalities after reading constant tables.
  Fixed a few typo in comments.

mysql-test/r/having.result

@@ -12,7 +12,7 @@ explain extended select count(a) as b from t1 where a=0 having b >=0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 Warnings:
-Note	1003	select count(`test`.`t1`.`a`) AS `b` from `test`.`t1` where (`test`.`t1`.`a` = 0) having (count(`test`.`t1`.`a`) >= 0)
+Note	1003	select count(`test`.`t1`.`a`) AS `b` from `test`.`t1` where 0 having (count(`test`.`t1`.`a`) >= 0)
 drop table t1;
 CREATE TABLE t1 (
 raw_id int(10) NOT NULL default '0',

mysql-test/r/select.result

@@ -3371,3 +3371,22 @@ NULL	a	NULL
 drop table t1,t2;
 select * from (select * left join t on f1=f2) tt;
 ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'on f1=f2) tt' at line 1
+CREATE TABLE t1 (sku int PRIMARY KEY, pr int);
+CREATE TABLE t2 (sku int PRIMARY KEY, sppr int, name varchar(255));
+INSERT INTO t1 VALUES
+(10, 10), (20, 10), (30, 20), (40, 30), (50, 10), (60, 10);
+INSERT INTO t2 VALUES 
+(10, 10, 'aaa'), (20, 10, 'bbb'), (30, 10, 'ccc'), (40, 20, 'ddd'),
+(50, 10, 'eee'), (60, 20, 'fff'), (70, 20, 'ggg'), (80, 30, 'hhh');
+SELECT t2.sku, t2.sppr, t2.name, t1.sku, t1.pr
+FROM t2, t1 WHERE t2.sku=20 AND (t2.sku=t1.sku OR t2.sppr=t1.sku);
+sku	sppr	name	sku	pr
+20	10	bbb	10	10
+20	10	bbb	20	10
+EXPLAIN
+SELECT t2.sku, t2.sppr, t2.name, t1.sku, t1.pr
+FROM t2, t1 WHERE t2.sku=20 AND (t2.sku=t1.sku OR t2.sppr=t1.sku);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	const	PRIMARY	PRIMARY	4	const	1	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	6	Using where
+DROP TABLE t1,t2;

mysql-test/r/subselect.result

@@ -547,7 +547,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	const	PRIMARY,numreponse	PRIMARY	7	const,const	1	Using index
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 Warnings:
-Note	1003	select `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'))
+Note	1003	select `test`.`t1`.`numreponse` AS `numreponse` from `test`.`t1` where ((`test`.`t1`.`numeropost` = _latin1'1'))
 drop table t1;
 CREATE TABLE t1 (a int(1));
 INSERT INTO t1 VALUES (1);

mysql-test/r/varbinary.result

@@ -15,7 +15,7 @@ explain extended select * from t1 where UNIQ=0x38afba1d73e6a18a;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	const	UNIQ	UNIQ	8	const	1	
 Warnings:
-Note	1003	select `test`.`t1`.`ID` AS `ID`,`test`.`t1`.`UNIQ` AS `UNIQ` from `test`.`t1` where (`test`.`t1`.`UNIQ` = 4084688022709641610)
+Note	1003	select `test`.`t1`.`ID` AS `ID`,`test`.`t1`.`UNIQ` AS `UNIQ` from `test`.`t1` where 1
 drop table t1;
 select x'hello';
 ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'x'hello'' at line 1

mysql-test/t/select.test

@@ -2848,3 +2848,26 @@ drop table t1,t2;
 #
 --error 1064
 select * from (select * left join t on f1=f2) tt;
+
+#
+# Bug #16504: re-evaluation of Item_equal object after reading const table
+#
+
+CREATE TABLE t1 (sku int PRIMARY KEY, pr int);
+CREATE TABLE t2 (sku int PRIMARY KEY, sppr int, name varchar(255));
+
+INSERT INTO t1 VALUES
+  (10, 10), (20, 10), (30, 20), (40, 30), (50, 10), (60, 10);
+
+INSERT INTO t2 VALUES 
+  (10, 10, 'aaa'), (20, 10, 'bbb'), (30, 10, 'ccc'), (40, 20, 'ddd'),
+  (50, 10, 'eee'), (60, 20, 'fff'), (70, 20, 'ggg'), (80, 30, 'hhh');
+
+SELECT t2.sku, t2.sppr, t2.name, t1.sku, t1.pr
+  FROM t2, t1 WHERE t2.sku=20 AND (t2.sku=t1.sku OR t2.sppr=t1.sku);
+EXPLAIN
+SELECT t2.sku, t2.sppr, t2.name, t1.sku, t1.pr
+  FROM t2, t1 WHERE t2.sku=20 AND (t2.sku=t1.sku OR t2.sppr=t1.sku);
+
+
+DROP TABLE t1,t2;

sql/item.cc

@@ -3744,7 +3744,7 @@ Item *Item_field::replace_equal_field(byte *arg)
   if (item_equal)
   {
     Item_field *subst= item_equal->get_first();
-    if (!field->eq(subst->field))
+    if (subst && !field->eq(subst->field))
       return subst;
   }
   return this;

sql/item_cmpfunc.cc

@@ -3602,7 +3602,8 @@ void Item_equal::add(Item *c)
   Item_func_eq *func= new Item_func_eq(c, const_item);
   func->set_cmp_func();
   func->quick_fix_field();
-  cond_false =  !(func->val_int());
+  if ((cond_false= !func->val_int()))
+    const_item_cache= 1;
 }
 
 void Item_equal::add(Item_field *f)
@@ -3734,13 +3735,45 @@ void Item_equal::sort(Item_field_cmpfunc cmp, void *arg)
   } while (swap);
 }
 
+
+/*
+  Check appearance of new constant items in the multiple equality object
+
+  SYNOPSIS
+    check()
+  
+  DESCRIPTION
+    The function checks appearance of new constant items among
+    the members of multiple equalities. Each new constant item is
+    compared with the designated constant item if there is any in the
+    multiple equality. If there is none the first new constant item
+    becomes designated.
+      
+  RETURN VALUES
+    none    
+*/
+
+void Item_equal::check_const()
+{
+  List_iterator<Item_field> it(fields);
+  Item *item;
+  while ((item= it++))
+  {
+    if (item->const_item())
+    {
+      it.remove();
+      add(item);
+    }
+  }
+}
+
 bool Item_equal::fix_fields(THD *thd, 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++))
+  while ((item= li++))
   {
     table_map tmp_table_map;
     used_tables_cache|= item->used_tables();

sql/item_cmpfunc.h

@@ -1196,6 +1196,7 @@ public:
   bool contains(Field *field);
   Item_field* get_first() { return fields.head(); }
   void merge(Item_equal *item);
+  void check_const();
   enum Functype functype() const { return MULT_EQUAL_FUNC; }
   longlong val_int(); 
   const char *func_name() const { return "multiple equal"; }

sql/sql_select.cc

@@ -136,7 +136,7 @@ static enum_nested_loop_state
 end_write_group(JOIN *join, JOIN_TAB *join_tab, bool end_of_records);
 
 static int test_if_group_changed(List<Cached_item> &list);
-static int join_read_const_table(JOIN_TAB *tab, POSITION *pos);
+static int join_read_const_table(JOIN *join, JOIN_TAB *tab, POSITION *pos);
 static int join_read_system(JOIN_TAB *tab);
 static int join_read_const(JOIN_TAB *tab);
 static int join_read_key(JOIN_TAB *tab);
@@ -2111,7 +2111,7 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables, COND *conds,
     s= p_pos->table;
     s->type=JT_SYSTEM;
     join->const_table_map|=s->table->map;
-    if ((tmp=join_read_const_table(s, p_pos)))
+    if ((tmp=join_read_const_table(join, s, p_pos)))
     {
       if (tmp > 0)
 	DBUG_RETURN(1);			// Fatal error
@@ -2148,7 +2148,8 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables, COND *conds,
 	  s->type=JT_SYSTEM;
 	  join->const_table_map|=table->map;
 	  set_position(join,const_count++,s,(KEYUSE*) 0);
-	  if ((tmp= join_read_const_table(s,join->positions+const_count-1)))
+	  if ((tmp= join_read_const_table(join, s,
+                                          join->positions+const_count-1)))
 	  {
 	    if (tmp > 0)
 	      DBUG_RETURN(1);			// Fatal error
@@ -2200,7 +2201,7 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables, COND *conds,
 	      if (create_ref_for_key(join, s, start_keyuse,
 				     found_const_table_map))
 		DBUG_RETURN(1);
-	      if ((tmp=join_read_const_table(s,
+	      if ((tmp=join_read_const_table(join, s,
 					     join->positions+const_count-1)))
 	      {
 		if (tmp > 0)
@@ -6796,8 +6797,8 @@ static COND *build_equal_items_for_cond(COND *cond,
       return item_equal;
     }
     /* 
-      For each field reference in cond, not from equalitym predicates,
-      set a pointer to the multiple equality if belongs to (if there is any)
+      For each field reference in cond, not from equal item predicates,
+      set a pointer to the multiple equality it belongs to (if there is any)
     */ 
     cond= cond->transform(&Item::equal_fields_propagator,
                             (byte *) inherited);
@@ -6982,7 +6983,7 @@ static int compare_fields_by_table_order(Item_field *field1,
 
   NOTES
     Before generating an equality function checks that it has not
-    been generated for multiple equalies of the upper levels.
+    been generated for multiple equalities of the upper levels.
     E.g. for the following where condition
     WHERE a=5 AND ((a=b AND b=c) OR  c>4)
     the upper level AND condition will contain =(5,a),
@@ -7155,7 +7156,7 @@ static COND* substitute_for_best_equal_field(COND *cond,
       {
         cond= eliminate_item_equal(cond, cond_equal->upper_levels, item_equal);
         // This occurs when eliminate_item_equal() founds that cond is
-        // always false and substitues it with Item_int 0.
+        // always false and substitutes it with Item_int 0.
         // Due to this, value of item_equal will be 0, so just return it.
         if (cond->type() != Item::COND_ITEM)
           break;
@@ -7177,6 +7178,45 @@ static COND* substitute_for_best_equal_field(COND *cond,
 }
 
 
+/* 
+  Check appearance of new constant items in multiple equalities
+  of a condition after reading a constant table
+ 
+  SYNOPSIS
+    check_const_equal_item()
+    cond       condition whose multiple equalities are to be checked
+    table      constant table that has been read 
+
+  DESCRIPTION
+    The function retrieves the cond condition and for each encountered
+    multiple equality checks whether new constants have appeared after
+    reading the constant (single row) table tab. If so it adjusts
+    the multiple equality appropriately.
+*/
+
+static void check_const_equal_items(COND *cond,
+                                    JOIN_TAB *tab)
+{
+  if (!(cond->used_tables() & tab->table->map))
+    return;
+
+  if (cond->type() == Item::COND_ITEM)
+  {
+    List<Item> *cond_list= ((Item_cond*) cond)->argument_list(); 
+    List_iterator_fast<Item> li(*cond_list);
+    Item *item;
+    while ((item= li++))
+      check_const_equal_items(item, tab);
+  }
+  else if (cond->type() == Item::FUNC_ITEM && 
+           ((Item_cond*) cond)->functype() == Item_func::MULT_EQUAL_FUNC)
+  {
+    Item_equal *item_equal= (Item_equal *) cond;
+    item_equal->check_const();
+  }
+}
+
+
 /*
   change field = field to field = const for each found field = const in the
   and_level
@@ -10099,7 +10139,7 @@ int safe_index_read(JOIN_TAB *tab)
 
 
 static int
-join_read_const_table(JOIN_TAB *tab, POSITION *pos)
+join_read_const_table(JOIN *join, JOIN_TAB *tab, POSITION *pos)
 {
   int error;
   DBUG_ENTER("join_read_const_table");
@@ -10151,6 +10191,26 @@ join_read_const_table(JOIN_TAB *tab, POSITION *pos)
   }
   if (!table->null_row)
     table->maybe_null=0;
+
+  /* Check appearance of new constant items in Item_equal objects */
+  if (join->conds)
+    check_const_equal_items(join->conds, tab);
+  TABLE_LIST *tbl;
+  for (tbl= join->select_lex->leaf_tables; tbl; tbl= tbl->next_leaf)
+  {
+    TABLE_LIST *embedded;
+    TABLE_LIST *embedding= tbl;
+    do
+    {
+      embedded= embedding;
+      if (embedded->on_expr)
+         check_const_equal_items(embedded->on_expr, tab);
+      embedding= embedded->embedding;
+    }
+    while (embedding &&
+           embedding->nested_join->join_list.head() == embedded);
+  }
+
   DBUG_RETURN(0);
 }