Another attempt to fix bug mdev-5103.

The earlier pushed fix for the bug was incomplete. It did not remove
the main cause of the problem: the function remove_eq_conds()
removed always true multiple equalities from any conjunct, but did not
adjust the list of them stored in Item_cond_and::cond_equal.current_level.

Simplified the test case for the bug and moved it to another test file.

The fix triggered changes in EXPLAIN EXTENDED for some queries. 

mysql-test/r/func_equal.result

@@ -43,46 +43,3 @@ a
 4828532208463511553
 drop table t1;
 #End of 4.1 tests
-#
-# MDEV-5103: server crashed on singular Item_equal
-#
-CREATE TABLE `t1` (
-`tipo` enum('p','r') NOT NULL DEFAULT 'r',
-`arquivo_id` bigint(20) unsigned NOT NULL DEFAULT '0',
-`arquivo_md5` char(32) NOT NULL,
-`conteudo` longblob NOT NULL,
-`usuario` varchar(15) NOT NULL,
-`datahora_gmt` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
-`tipo_arquivo` varchar(255) NOT NULL,
-`nome_arquivo` varchar(255) NOT NULL,
-`tamanho_arquivo` bigint(20) unsigned NOT NULL DEFAULT '0',
-PRIMARY KEY (`tipo`,`arquivo_id`),
-UNIQUE KEY `tipo` (`tipo`,`arquivo_md5`)
-) ENGINE=Aria DEFAULT CHARSET=latin1 PAGE_CHECKSUM=1;
-INSERT INTO `t1` (`tipo`, `arquivo_id`, `arquivo_md5`, `conteudo`, `usuario`, `datahora_gmt`, `tipo_arquivo`, `nome_arquivo`, `tamanho_arquivo`) VALUES
-('r', 1, 'ad18832202b199728921807033a8a515', '', 'rspadim', '2013-10-05 13:55:50', '001_cbr643', 'CBR6431677410201314132.ret', 21306);
-CREATE TABLE `t2` (
-`tipo` enum('p','r') NOT NULL DEFAULT 'p',
-`arquivo_id` bigint(20) NOT NULL DEFAULT '0',
-`usuario` varchar(25) NOT NULL,
-`datahora` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
-`erros` longblob NOT NULL,
-`importados` bigint(20) unsigned NOT NULL DEFAULT '0',
-`n_importados` bigint(20) unsigned NOT NULL DEFAULT '0',
-PRIMARY KEY (`tipo`,`arquivo_id`,`datahora`)
-) ENGINE=Aria DEFAULT CHARSET=latin1 PAGE_CHECKSUM=1;
-INSERT INTO `t2` (`tipo`, `arquivo_id`, `usuario`, `datahora`, `erros`, `importados`, `n_importados`) VALUES
-('r', 1, 'rspadim', '2013-10-05 14:25:30', '', 32, 0);
-SELECT
-arquivo_id,usuario,datahora_gmt,tipo_arquivo,nome_arquivo,tamanho_arquivo
-FROM t1 AS a
-WHERE datahora_gmt>='0000-00-00 00:00:00' AND
-datahora_gmt<='2013-10-07 02:59:59' AND tipo='r' AND
-(tipo_arquivo,arquivo_id) NOT IN
-(SELECT tipo_arquivo,arquivo_id
-FROM t2
-WHERE (tipo_arquivo,arquivo_id)=(a.tipo_arquivo,a.arquivo_id))
-ORDER BY arquivo_id DESC;
-arquivo_id	usuario	datahora_gmt	tipo_arquivo	nome_arquivo	tamanho_arquivo
-drop table t2, t1;
-#End of 5.3 tests

mysql-test/r/join_outer.result

@@ -1773,7 +1773,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	const	PRIMARY,idx	PRIMARY	4	const	1	100.00	
 1	SIMPLE	t2	const	PRIMARY	PRIMARY	4	const	1	100.00	Using index
 Warnings:
-Note	1003	select 5 AS `pk` from `test`.`t2` join `test`.`t1` where ((((1 between 5 and 6) and isnull(5)) or 1)) order by 5
+Note	1003	select 5 AS `pk` from `test`.`t2` join `test`.`t1` where 1 order by 5
 SELECT t1.pk FROM t2 LEFT JOIN t1 ON t2.pk = t1.a
 WHERE t1.b BETWEEN 5 AND 6 AND t1.pk IS NULL OR t1.pk = 5
 ORDER BY t1.pk;

mysql-test/r/join_outer_jcl6.result

@@ -1784,7 +1784,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	const	PRIMARY,idx	PRIMARY	4	const	1	100.00	
 1	SIMPLE	t2	const	PRIMARY	PRIMARY	4	const	1	100.00	Using index
 Warnings:
-Note	1003	select 5 AS `pk` from `test`.`t2` join `test`.`t1` where ((((1 between 5 and 6) and isnull(5)) or 1)) order by 5
+Note	1003	select 5 AS `pk` from `test`.`t2` join `test`.`t1` where 1 order by 5
 SELECT t1.pk FROM t2 LEFT JOIN t1 ON t2.pk = t1.a
 WHERE t1.b BETWEEN 5 AND 6 AND t1.pk IS NULL OR t1.pk = 5
 ORDER BY t1.pk;

mysql-test/r/select.result

@@ -5125,7 +5125,7 @@ SELECT * FROM t1 WHERE (1=2 OR t1.pk=2) AND t1.a <> 0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 Warnings:
-Note	1003	select 2 AS `pk`,0 AS `a` from `test`.`t1` where ((0 <> 0))
+Note	1003	select 2 AS `pk`,0 AS `a` from `test`.`t1` where (0 <> 0)
 DROP TABLE t1;
 SELECT * FROM mysql.time_zone 
 WHERE ( NOT (Use_leap_seconds <= Use_leap_seconds AND Time_zone_id != 1) 

mysql-test/r/select_jcl6.result

@@ -5136,7 +5136,7 @@ SELECT * FROM t1 WHERE (1=2 OR t1.pk=2) AND t1.a <> 0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 Warnings:
-Note	1003	select 2 AS `pk`,0 AS `a` from `test`.`t1` where ((0 <> 0))
+Note	1003	select 2 AS `pk`,0 AS `a` from `test`.`t1` where (0 <> 0)
 DROP TABLE t1;
 SELECT * FROM mysql.time_zone 
 WHERE ( NOT (Use_leap_seconds <= Use_leap_seconds AND Time_zone_id != 1) 

mysql-test/r/select_pkeycache.result

@@ -5125,7 +5125,7 @@ SELECT * FROM t1 WHERE (1=2 OR t1.pk=2) AND t1.a <> 0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 Warnings:
-Note	1003	select 2 AS `pk`,0 AS `a` from `test`.`t1` where ((0 <> 0))
+Note	1003	select 2 AS `pk`,0 AS `a` from `test`.`t1` where (0 <> 0)
 DROP TABLE t1;
 SELECT * FROM mysql.time_zone 
 WHERE ( NOT (Use_leap_seconds <= Use_leap_seconds AND Time_zone_id != 1) 

mysql-test/r/subselect4.result

@@ -2326,5 +2326,27 @@ x	NULL	NULL	NULL
 d	NULL	NULL	NULL
 drop table t1,t2;
 set @@optimizer_switch = @optimizer_switch_MDEV4056;
+#
+# MDEV-5103: server crashed on singular Item_equal
+#
+CREATE TABLE t1 (
+a enum('p','r') NOT NULL DEFAULT 'r',
+b int NOT NULL DEFAULT '0',
+c char(32) NOT NULL,
+d varchar(255) NOT NULL,
+PRIMARY KEY (a, b), UNIQUE KEY idx(a, c)
+);
+INSERT INTO t1 VALUES ('r', 1, 'ad18832202b199728921807033a8a515', '001_cbr643');
+CREATE TABLE t2 (
+a enum('p','r') NOT NULL DEFAULT 'r',
+b int NOT NULL DEFAULT '0',
+e datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
+PRIMARY KEY (a, b, e)
+);
+INSERT INTO t2 VALUES ('r', 1, '2013-10-05 14:25:30');
+SELECT * FROM t1 AS t 
+WHERE a='r' AND (c,b) NOT IN (SELECT c,b FROM t2 WHERE (c,b)=(t.c,t.b));
+a	b	c	d
+DROP TABLE t1, t2;
 SET optimizer_switch= @@global.optimizer_switch;
 set @@tmp_table_size= @@global.tmp_table_size;

mysql-test/r/subselect_extra.result

@@ -46,7 +46,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 Warnings:
 Note	1276	Field or reference 'test.t1.cur_date' of SELECT #2 was resolved in SELECT #1
-Note	1003	select 1 AS `id`,'2007-04-25 18:30:22' AS `cur_date` from `test`.`t1` semi join (`test`.`t1` `x1`) where (('2007-04-25 18:30:22' = 0))
+Note	1003	select 1 AS `id`,'2007-04-25 18:30:22' AS `cur_date` from `test`.`t1` semi join (`test`.`t1` `x1`) where ('2007-04-25 18:30:22' = 0)
 select * from t1
 where id in (select id from t1 as x1 where (t1.cur_date is null));
 id	cur_date
@@ -57,7 +57,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 Warnings:
 Note	1276	Field or reference 'test.t2.cur_date' of SELECT #2 was resolved in SELECT #1
-Note	1003	select 1 AS `id`,'2007-04-25' AS `cur_date` from `test`.`t2` semi join (`test`.`t2` `x1`) where (('2007-04-25' = 0))
+Note	1003	select 1 AS `id`,'2007-04-25' AS `cur_date` from `test`.`t2` semi join (`test`.`t2` `x1`) where ('2007-04-25' = 0)
 select * from t2
 where id in (select id from t2 as x1 where (t2.cur_date is null));
 id	cur_date

mysql-test/r/type_datetime.result

@@ -519,7 +519,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 Warnings:
 Note	1276	Field or reference 'test.t1.cur_date' of SELECT #2 was resolved in SELECT #1
-Note	1003	select 1 AS `id`,'2007-04-25 18:30:22' AS `cur_date` from `test`.`t1` semi join (`test`.`t1` `x1`) where (('2007-04-25 18:30:22' = 0))
+Note	1003	select 1 AS `id`,'2007-04-25 18:30:22' AS `cur_date` from `test`.`t1` semi join (`test`.`t1` `x1`) where ('2007-04-25 18:30:22' = 0)
 select * from t1
 where id in (select id from t1 as x1 where (t1.cur_date is null));
 id	cur_date
@@ -530,7 +530,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 Warnings:
 Note	1276	Field or reference 'test.t2.cur_date' of SELECT #2 was resolved in SELECT #1
-Note	1003	select 1 AS `id`,'2007-04-25' AS `cur_date` from `test`.`t2` semi join (`test`.`t2` `x1`) where (('2007-04-25' = 0))
+Note	1003	select 1 AS `id`,'2007-04-25' AS `cur_date` from `test`.`t2` semi join (`test`.`t2` `x1`) where ('2007-04-25' = 0)
 select * from t2
 where id in (select id from t2 as x1 where (t2.cur_date is null));
 id	cur_date

mysql-test/t/func_equal.test

@@ -44,53 +44,3 @@ select * from t1 where a in ('4828532208463511553');
 drop table t1;
 
 --echo #End of 4.1 tests
-
---echo #
---echo # MDEV-5103: server crashed on singular Item_equal
---echo #
-
-CREATE TABLE `t1` (
-  `tipo` enum('p','r') NOT NULL DEFAULT 'r',
-  `arquivo_id` bigint(20) unsigned NOT NULL DEFAULT '0',
-  `arquivo_md5` char(32) NOT NULL,
-  `conteudo` longblob NOT NULL,
-  `usuario` varchar(15) NOT NULL,
-  `datahora_gmt` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
-  `tipo_arquivo` varchar(255) NOT NULL,
-  `nome_arquivo` varchar(255) NOT NULL,
-  `tamanho_arquivo` bigint(20) unsigned NOT NULL DEFAULT '0',
-  PRIMARY KEY (`tipo`,`arquivo_id`),
-  UNIQUE KEY `tipo` (`tipo`,`arquivo_md5`)
-) ENGINE=Aria DEFAULT CHARSET=latin1 PAGE_CHECKSUM=1;
-
-INSERT INTO `t1` (`tipo`, `arquivo_id`, `arquivo_md5`, `conteudo`, `usuario`, `datahora_gmt`, `tipo_arquivo`, `nome_arquivo`, `tamanho_arquivo`) VALUES
-	('r', 1, 'ad18832202b199728921807033a8a515', '', 'rspadim', '2013-10-05 13:55:50', '001_cbr643', 'CBR6431677410201314132.ret', 21306);
-
-
-CREATE TABLE `t2` (
-  `tipo` enum('p','r') NOT NULL DEFAULT 'p',
-  `arquivo_id` bigint(20) NOT NULL DEFAULT '0',
-  `usuario` varchar(25) NOT NULL,
-  `datahora` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
-  `erros` longblob NOT NULL,
-  `importados` bigint(20) unsigned NOT NULL DEFAULT '0',
-  `n_importados` bigint(20) unsigned NOT NULL DEFAULT '0',
-  PRIMARY KEY (`tipo`,`arquivo_id`,`datahora`)
-) ENGINE=Aria DEFAULT CHARSET=latin1 PAGE_CHECKSUM=1;
-
-INSERT INTO `t2` (`tipo`, `arquivo_id`, `usuario`, `datahora`, `erros`, `importados`, `n_importados`) VALUES
-	('r', 1, 'rspadim', '2013-10-05 14:25:30', '', 32, 0);
-
-SELECT
-arquivo_id,usuario,datahora_gmt,tipo_arquivo,nome_arquivo,tamanho_arquivo
-  FROM t1 AS a
-  WHERE datahora_gmt>='0000-00-00 00:00:00' AND
-    datahora_gmt<='2013-10-07 02:59:59' AND tipo='r' AND
-    (tipo_arquivo,arquivo_id) NOT IN
-      (SELECT tipo_arquivo,arquivo_id
-        FROM t2
-        WHERE (tipo_arquivo,arquivo_id)=(a.tipo_arquivo,a.arquivo_id))
-  ORDER BY arquivo_id DESC;
-
-drop table t2, t1;
---echo #End of 5.3 tests

mysql-test/t/subselect4.test

@@ -1910,7 +1910,31 @@ WHERE b IS NULL OR a < 'u';
 drop table t1,t2;
 set @@optimizer_switch = @optimizer_switch_MDEV4056;
 
+--echo #
+--echo # MDEV-5103: server crashed on singular Item_equal
+--echo #
+
+CREATE TABLE t1 (
+  a enum('p','r') NOT NULL DEFAULT 'r',
+  b int NOT NULL DEFAULT '0',
+  c char(32) NOT NULL,
+  d varchar(255) NOT NULL,
+  PRIMARY KEY (a, b), UNIQUE KEY idx(a, c)
+);
+INSERT INTO t1 VALUES ('r', 1, 'ad18832202b199728921807033a8a515', '001_cbr643');
+
+CREATE TABLE t2 (
+  a enum('p','r') NOT NULL DEFAULT 'r',
+  b int NOT NULL DEFAULT '0',
+  e datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
+  PRIMARY KEY (a, b, e)
+);
+INSERT INTO t2 VALUES ('r', 1, '2013-10-05 14:25:30');
+
+SELECT * FROM t1 AS t 
+  WHERE a='r' AND (c,b) NOT IN (SELECT c,b FROM t2 WHERE (c,b)=(t.c,t.b));
 
+DROP TABLE t1, t2;
 
 SET optimizer_switch= @@global.optimizer_switch;
 set @@tmp_table_size= @@global.tmp_table_size;

sql/item_cmpfunc.cc

@@ -5485,7 +5485,8 @@ Item *Item_bool_rowready_func2::negated_item()
 */
 
 Item_equal::Item_equal(Item *f1, Item *f2, bool with_const_item)
-  : Item_bool_func(), eval_item(0), cond_false(0), context_field(NULL)
+  : Item_bool_func(), eval_item(0), cond_false(0), cond_true(0), 
+    context_field(NULL)
 {
   const_item_cache= 0;
   with_const= with_const_item;
@@ -5510,7 +5511,8 @@ Item_equal::Item_equal(Item *f1, Item *f2, bool with_const_item)
 */
 
 Item_equal::Item_equal(Item_equal *item_equal)
-  : Item_bool_func(), eval_item(0), cond_false(0), context_field(NULL)
+  : Item_bool_func(), eval_item(0), cond_false(0), cond_true(0),
+     context_field(NULL)
 {
   const_item_cache= 0;
   List_iterator_fast<Item> li(item_equal->equal_items);
@@ -5569,12 +5571,6 @@ void Item_equal::add_const(Item *c, Item *f)
     func->quick_fix_field();
     cond_false= !func->val_int();
   }
-  /*
-    TODO: also support the case where Item_equal becomes singular with
-    this->is_cond_true()=1.  When I attempted to mark the item as constant,
-    the optimizer attempted to remove it, however it is still referenced from
-    COND_EQUAL and I got a crash.
-  */
   if (cond_false)
     const_item_cache= 1;
 }
@@ -5779,8 +5775,7 @@ void Item_equal::merge_into_list(List<Item_equal> *list,
 
 void Item_equal::sort(Item_field_cmpfunc compare, void *arg)
 {
-  if (equal_items.elements > 1)
-    bubble_sort<Item>(&equal_items, compare, arg);
+  bubble_sort<Item>(&equal_items, compare, arg);
 }
 
 
@@ -5816,6 +5811,9 @@ void Item_equal::update_const()
       {
         it.remove();
         add_const(item);
+        if (equal_items.elements == 1)
+          cond_true= TRUE;
+        update_used_tables();
       }
     } 
   }
@@ -5880,13 +5878,7 @@ bool Item_equal::fix_fields(THD *thd, Item **ref)
 void Item_equal::update_used_tables()
 {
   not_null_tables_cache= used_tables_cache= 0;
-  /*
-    TODO: also support the case where Item_equal becomes singular with
-    this->is_cond_true()=1.  When I attempted to mark the item as constant,
-    the optimizer attempted to remove it, however it is still referenced from
-    COND_EQUAL and I got a crash.
-  */
-  if ((const_item_cache= cond_false))
+  if ((const_item_cache= cond_false || cond_true))
     return;
   Item_equal_fields_iterator it(*this);
   Item *item;
@@ -5934,7 +5926,7 @@ longlong Item_equal::val_int()
 {
   if (cond_false)
     return 0;
-  if (is_cond_true())
+  if (cond_true)
     return 1;
   Item *item= get_const();
   Item_equal_fields_iterator it(*this);
@@ -5960,11 +5952,6 @@ longlong Item_equal::val_int()
 void Item_equal::fix_length_and_dec()
 {
   Item *item= get_first(NO_PARTICULAR_TAB, NULL);
-  if (!item)
-  {
-    DBUG_ASSERT(is_cond_true()); // it should be the only constant
-    item= equal_items.head();
-  }
   eval_item= cmp_item::get_comparator(item->cmp_type(), item,
                                       item->collation.collation);
 }

sql/item_cmpfunc.h

@@ -1695,6 +1695,12 @@ class Item_equal: public Item_bool_func
     the equal_items should be ignored.
   */
   bool cond_false;
+  /*
+    This initially is set to FALSE. It becomes TRUE when this item is evaluated
+    as being always true. If the flag is TRUE the contents of the list 
+    the equal_items should be ignored.
+  */
+  bool cond_true;
   /* 
     compare_as_dates=TRUE <-> constants equal to fields from equal_items
     must be compared as datetimes and not as strings.
@@ -1725,7 +1731,6 @@ public:
   Item_equal(Item_equal *item_equal);
   /* Currently the const item is always the first in the list of equal items */
   inline Item* get_const() { return with_const ? equal_items.head() : NULL; }
-  inline bool is_cond_true() { return equal_items.elements == 1; }
   void add_const(Item *c, Item *f = NULL);
   /** Add a non-constant item to the multiple equality */
   void add(Item *f) { equal_items.push_back(f); }

sql/sql_select.cc

@@ -13394,16 +13394,44 @@ remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value)
 {
   if (cond->type() == Item::COND_ITEM)
   {
-    List<Item_equal> new_equalities;
     bool and_level= ((Item_cond*) cond)->functype()
       == Item_func::COND_AND_FUNC;
     List<Item> *cond_arg_list= ((Item_cond*) cond)->argument_list();
+
+    if (and_level)
+    {
+      /* 
+        Remove multiple equalities that became always true (e.g. after
+        constant row substitution).
+        They would be removed later in the function anyway, but the list of
+        them cond_equal.current_level also  must be adjusted correspondingly.
+        So it's easier  to do it at one pass through the list of the equalities.
+      */ 
+       List<Item_equal> *cond_equalities=
+        &((Item_cond_and *) cond)->cond_equal.current_level;
+       cond_arg_list->disjoin((List<Item> *) cond_equalities);
+       List_iterator<Item_equal> it(*cond_equalities);
+       Item_equal *eq_item;
+       while ((eq_item= it++))
+       {
+         if (eq_item->const_item() && eq_item->val_int())
+           it.remove();
+       }  
+       cond_arg_list->concat((List<Item> *) cond_equalities);       
+    }
+
+    List<Item_equal> new_equalities;
     List_iterator<Item> li(*cond_arg_list);
+    bool should_fix_fields= 0;
     Item::cond_result tmp_cond_value;
-    bool should_fix_fields=0;
-
-    *cond_value=Item::COND_UNDEF;
     Item *item;
+
+    /* 
+      If the list cond_arg_list became empty then it consisted only
+      of always true multiple equalities.
+    */ 
+    *cond_value= cond_arg_list->elements ? Item::COND_UNDEF : Item::COND_TRUE;
+
     while ((item=li++))
     {
       Item *new_item=remove_eq_conds(thd, item, &tmp_cond_value);