BUG#727667 Wrong result with OR + NOT NULL in maria-5.3

- put the code that sets HA_NULL_PART bit back
- Fix test_if_ref/part_of_refkey() so that 
  = NULL-ability of lookup columns does not prevent the equality 
    from being removed (we now have early/late NULLs filtering which 
    will filter out NULL values)
  = equality is not removed if it is ref_or_null access, and the value 
    of the lookup column can alternate between the lookup value and NULL.

mysql-test/r/null.result

@@ -170,7 +170,7 @@ insert into t1 select i*2 from t1;
 insert into t1 values(null);
 explain select * from t1 where i=2 or i is null;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref_or_null	i	i	5	const	9	Using index
+1	SIMPLE	t1	ref_or_null	i	i	5	const	9	Using where; Using index
 select count(*) from t1 where i=2 or i is null;
 count(*)
 10

mysql-test/r/null_key.result

@@ -21,10 +21,10 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	a,b	a	9	NULL	3	Using where; Using index
 explain select * from t1 where (a is null or a = 7) and b=7;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref_or_null	a,b	a	9	const,const	2	Using index
+1	SIMPLE	t1	ref_or_null	a,b	a	9	const,const	2	Using where; Using index
 explain select * from t1 where (a is null or a = 7) and b=7 order by a;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref_or_null	a,b	a	9	const,const	2	Using index; Using filesort
+1	SIMPLE	t1	ref_or_null	a,b	a	9	const,const	2	Using where; Using index; Using filesort
 explain select * from t1 where (a is null and b>a) or a is null and b=7 limit 2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	a,b	a	5	const	3	Using where; Using index
@@ -151,7 +151,7 @@ alter table t1 modify b int null;
 insert into t1 values (7,null), (8,null), (8,7);
 explain select * from t1 where a = 7 and (b=7 or b is null);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref_or_null	a,b	a	10	const,const	2	Using index
+1	SIMPLE	t1	ref_or_null	a,b	a	10	const,const	2	Using where; Using index
 select * from t1 where a = 7 and (b=7 or b is null);
 a	b
 7	7
@@ -166,7 +166,7 @@ a	b
 NULL	7
 explain select * from t1 where (a = 7 or a is null) and (a = 7 or a is null);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref_or_null	a	a	5	const	5	Using index
+1	SIMPLE	t1	ref_or_null	a	a	5	const	5	Using where; Using index
 select * from t1 where (a = 7 or a is null) and (a = 7 or a is null);
 a	b
 7	NULL
@@ -192,7 +192,7 @@ a	a	b
 explain select * from t2,t1 where t1.a=t2.a and (b= 7 or b is null);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
-1	SIMPLE	t1	ref_or_null	a	a	10	test.t2.a,const	4	Using index
+1	SIMPLE	t1	ref_or_null	a	a	10	test.t2.a,const	4	Using where; Using index
 select * from t2,t1 where t1.a=t2.a and (b= 7 or b is null);
 a	a	b
 7	7	7
@@ -202,7 +202,7 @@ a	a	b
 explain select * from t2,t1 where (t1.a=t2.a or t1.a is null) and b= 7;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	2	
-1	SIMPLE	t1	ref_or_null	a	a	10	test.t2.a,const	4	Using index
+1	SIMPLE	t1	ref_or_null	a	a	10	test.t2.a,const	4	Using where; Using index
 select * from t2,t1 where (t1.a=t2.a or t1.a is null) and b= 7;
 a	a	b
 7	7	7
@@ -226,7 +226,7 @@ delete from t1 where a=8;
 explain select * from t2,t1 where t1.a=t2.a or t1.a is null;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	4	
-1	SIMPLE	t1	ref_or_null	a	a	5	test.t2.a	4	Using index
+1	SIMPLE	t1	ref_or_null	a	a	5	test.t2.a	4	Using where; Using index
 explain select * from t2,t1 where t1.a<=>t2.a or (t1.a is null and t1.b <> 9);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	4	
@@ -447,3 +447,15 @@ a	b	a	b
 3	12	0	12
 drop table t1, t2;
 End of 5.0 tests
+#
+#  BUG#727667 Wrong result with OR + NOT NULL in maria-5.3
+# 
+CREATE TABLE t1 (
+f3 int(11),
+f10 varchar(1),
+KEY (f3)
+);
+INSERT INTO t1 VALUES ('9','k'),(NULL,'r');
+SELECT * FROM t1 WHERE (f3 = 83) OR (f10 = 'z' AND f3 IS NULL);
+f3	f10
+DROP TABLE t1;

mysql-test/r/order_by.result

@@ -643,7 +643,7 @@ create table t1(a int, b int, index(b));
 insert into t1 values (2, 1), (1, 1), (4, NULL), (3, NULL), (6, 2), (5, 2);
 explain select * from t1 where b=1 or b is null order by a;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref_or_null	b	b	5	const	3	Using filesort
+1	SIMPLE	t1	ref_or_null	b	b	5	const	3	Using index condition; Using filesort
 select * from t1 where b=1 or b is null order by a;
 a	b
 1	1
@@ -652,7 +652,7 @@ a	b
 4	NULL
 explain select * from t1 where b=2 or b is null order by a;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref_or_null	b	b	5	const	4	Using filesort
+1	SIMPLE	t1	ref_or_null	b	b	5	const	4	Using index condition; Using filesort
 select * from t1 where b=2 or b is null order by a;
 a	b
 3	NULL

mysql-test/r/subselect.result

@@ -906,7 +906,7 @@ a	t1.a in (select t2.a from t2,t3 where t3.a=t2.a)
 explain extended SELECT t1.a, t1.a in (select t2.a from t2,t3 where t3.a=t2.a) FROM t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	index	NULL	PRIMARY	4	NULL	4	100.00	Using index
-2	DEPENDENT SUBQUERY	t2	ref_or_null	a	a	5	func	2	100.00	Using index
+2	DEPENDENT SUBQUERY	t2	ref_or_null	a	a	5	func	2	100.00	Using where; Using index
 2	DEPENDENT SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where; Using join buffer (flat, BNL join)
 Warnings:
 Note	1003	select `test`.`t1`.`a` AS `a`,<expr_cache><`test`.`t1`.`a`>(<in_optimizer>(`test`.`t1`.`a`,<exists>(select 1 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`)))) AS `t1.a in (select t2.a from t2,t3 where t3.a=t2.a)` from `test`.`t1`

mysql-test/r/subselect_no_mat.result

@@ -910,7 +910,7 @@ a	t1.a in (select t2.a from t2,t3 where t3.a=t2.a)
 explain extended SELECT t1.a, t1.a in (select t2.a from t2,t3 where t3.a=t2.a) FROM t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	index	NULL	PRIMARY	4	NULL	4	100.00	Using index
-2	DEPENDENT SUBQUERY	t2	ref_or_null	a	a	5	func	2	100.00	Using index
+2	DEPENDENT SUBQUERY	t2	ref_or_null	a	a	5	func	2	100.00	Using where; Using index
 2	DEPENDENT SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where; Using join buffer (flat, BNL join)
 Warnings:
 Note	1003	select `test`.`t1`.`a` AS `a`,<expr_cache><`test`.`t1`.`a`>(<in_optimizer>(`test`.`t1`.`a`,<exists>(select 1 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`)))) AS `t1.a in (select t2.a from t2,t3 where t3.a=t2.a)` from `test`.`t1`

mysql-test/r/subselect_no_opts.result

@@ -907,7 +907,7 @@ a	t1.a in (select t2.a from t2,t3 where t3.a=t2.a)
 explain extended SELECT t1.a, t1.a in (select t2.a from t2,t3 where t3.a=t2.a) FROM t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	index	NULL	PRIMARY	4	NULL	4	100.00	Using index
-2	DEPENDENT SUBQUERY	t2	ref_or_null	a	a	5	func	2	100.00	Using index
+2	DEPENDENT SUBQUERY	t2	ref_or_null	a	a	5	func	2	100.00	Using where; Using index
 2	DEPENDENT SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where; Using join buffer (flat, BNL join)
 Warnings:
 Note	1003	select `test`.`t1`.`a` AS `a`,<expr_cache><`test`.`t1`.`a`>(<in_optimizer>(`test`.`t1`.`a`,<exists>(select 1 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`)))) AS `t1.a in (select t2.a from t2,t3 where t3.a=t2.a)` from `test`.`t1`

mysql-test/r/subselect_no_semijoin.result

@@ -907,7 +907,7 @@ a	t1.a in (select t2.a from t2,t3 where t3.a=t2.a)
 explain extended SELECT t1.a, t1.a in (select t2.a from t2,t3 where t3.a=t2.a) FROM t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	index	NULL	PRIMARY	4	NULL	4	100.00	Using index
-2	DEPENDENT SUBQUERY	t2	ref_or_null	a	a	5	func	2	100.00	Using index
+2	DEPENDENT SUBQUERY	t2	ref_or_null	a	a	5	func	2	100.00	Using where; Using index
 2	DEPENDENT SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where; Using join buffer (flat, BNL join)
 Warnings:
 Note	1003	select `test`.`t1`.`a` AS `a`,<expr_cache><`test`.`t1`.`a`>(<in_optimizer>(`test`.`t1`.`a`,<exists>(select 1 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`)))) AS `t1.a in (select t2.a from t2,t3 where t3.a=t2.a)` from `test`.`t1`

mysql-test/t/null_key.test

@@ -263,3 +263,16 @@ SELECT * FROM t2 inner join t1 WHERE ( t1.a = 0 OR t1.a IS NULL) AND t2.a = 3 AN
 drop table t1, t2;
 -- echo End of 5.0 tests
 
+--echo #
+--echo #  BUG#727667 Wrong result with OR + NOT NULL in maria-5.3
+--echo # 
+
+CREATE TABLE t1 (
+        f3 int(11),
+        f10 varchar(1),
+        KEY (f3)
+);
+INSERT INTO t1 VALUES ('9','k'),(NULL,'r');
+SELECT * FROM t1 WHERE (f3 = 83) OR (f10 = 'z' AND f3 IS NULL);
+DROP TABLE t1;
+

sql/sql_select.cc

@@ -6564,10 +6564,12 @@ static bool create_ref_for_key(JOIN *join, JOIN_TAB *j,
   j->ref.has_record= FALSE;
   j->ref.null_rejecting= 0;
   j->ref.disable_cache= FALSE;
+  j->ref.null_ref_part= (uint)-1;
   keyuse=org_keyuse;
 
   store_key **ref_key= j->ref.key_copy;
   uchar *key_buff=j->ref.key_buff, *null_ref_key= 0;
+  uint null_ref_part= (uint)-1;
   bool keyuse_uses_no_tables= TRUE;
   if (ftkey)
   {
@@ -6621,7 +6623,10 @@ static bool create_ref_for_key(JOIN *join, JOIN_TAB *j,
 	instead of JT_REF_OR_NULL in case if field can't be null
       */
       if ((keyuse->optimize & KEY_OPTIMIZE_REF_OR_NULL) && maybe_null)
+      {
 	null_ref_key= key_buff;
+        null_ref_part= i;
+      }
       key_buff+= keyinfo->key_part[i].store_length;
     }
   } /* not ftkey */
@@ -6636,6 +6641,7 @@ static bool create_ref_for_key(JOIN *join, JOIN_TAB *j,
     /* Must read with repeat */
     j->type= null_ref_key ? JT_REF_OR_NULL : JT_REF;
     j->ref.null_ref_key= null_ref_key;
+    j->ref.null_ref_part= null_ref_part;
   }
   else if (keyuse_uses_no_tables)
   {
@@ -15287,8 +15293,12 @@ end_write_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
 *****************************************************************************/
 
 /**
+  Check if "left_item=right_item" equality is guaranteed to be true by use of
+  [eq]ref access on left_item->field->table.
+
   @return
-    1 if right_item is used removable reference key on left_item
+    TRUE    if right_item is used removable reference key on left_item
+    FALSE   otherwise
 */
 
 bool test_if_ref(Item *root_cond, Item_field *left_item,Item *right_item)
@@ -15301,7 +15311,11 @@ bool test_if_ref(Item *root_cond, Item_field *left_item,Item *right_item)
       (!join_tab->first_inner ||
        *join_tab->first_inner->on_expr_ref == root_cond))
   {
-    // Cond guards
+    /*
+      If ref access uses "Full scan on NULL key" (i.e. it actually alternates
+      between ref access and full table scan), then no equality can be
+      guaranteed to be true.
+    */
     for (uint i = 0; i < join_tab->ref.key_parts; i++)
     {
       if (join_tab->ref.cond_guards[i])
@@ -15309,7 +15323,7 @@ bool test_if_ref(Item *root_cond, Item_field *left_item,Item *right_item)
         return FALSE;
       }
     }
-    //
+
     Item *ref_item=part_of_refkey(field->table,field);
     if (ref_item && ref_item->eq(right_item,1))
     {
@@ -15611,6 +15625,29 @@ make_cond_after_sjm(Item *root_cond, Item *cond, table_map tables,
 }
 
 
+/*
+  @brief
+
+  Check if
+   - @table uses "ref"-like access 
+   - it is based on "@field=certain_item" equality
+   - the equality will be true for any record returned by the access method
+  and return the certain_item if yes.
+  
+  @detail
+  
+  Equality won't necessarily hold if:
+   - the used index covers only part of the @field. 
+     Suppose, we have a CHAR(5) field and INDEX(field(3)). if you make a lookup
+     for 'abc', you will get both record with 'abc' and with 'abcde'.
+   - The type of access is actually ref_or_null, and so @field can be either 
+     a value or NULL.
+
+  @return 
+    Item that the field will be equal to
+    NULL if no such item 
+*/
+
 static Item *
 part_of_refkey(TABLE *table,Field *field)
 {
@@ -15619,17 +15656,30 @@ part_of_refkey(TABLE *table,Field *field)
     return (Item*) 0;             // field from outer non-select (UPDATE,...)
 
   uint ref_parts= join_tab->ref.key_parts;
-  if (ref_parts)
+  if (ref_parts) /* if it's ref/eq_ref/ref_or_null */
   {
-    
     uint key= join_tab->ref.key;
     KEY *key_info= join_tab->get_keyinfo_by_key_no(key);
     KEY_PART_INFO *key_part= key_info->key_part;
 
     for (uint part=0 ; part < ref_parts ; part++,key_part++)
-      if (field->eq(key_part->field) &&
-	  !(key_part->key_part_flag & (HA_PART_KEY_SEG | HA_NULL_PART)))
-	return join_tab->ref.items[part];
+    {
+      if (field->eq(key_part->field))
+      {
+        /*
+          Found the field in the key. Check that 
+           1. ref_or_null doesn't alternate this component between a value and
+              a NULL
+           2. index fully covers the key
+        */
+        if (part != join_tab->ref.null_ref_part &&            // (1)
+            !(key_part->key_part_flag & HA_PART_KEY_SEG))     // (2)
+        {
+          return join_tab->ref.items[part];
+        }
+        break;
+      }
+    }
   }
   return (Item*) 0;
 }

sql/sql_select.h

@@ -109,8 +109,15 @@ typedef struct st_table_ref
   */
   key_part_map  null_rejecting;
   table_map	depend_map;		  ///< Table depends on these tables.
+
   /* null byte position in the key_buf. Used for REF_OR_NULL optimization */
   uchar          *null_ref_key;
+  /* 
+    ref_or_null optimization: number of key part can be NULL (there's only one)
+    uint(-1) if no part can be NULL.
+  */
+  uint           null_ref_part;
+
   /*
     The number of times the record associated with this key was used
     in the join.

sql/table.cc

@@ -1581,6 +1581,8 @@ static int open_binary_frm(THD *thd, TABLE_SHARE *share, uchar *head,
 #endif
           key_part->key_part_flag|= HA_PART_KEY_SEG;
         }
+        if (field->real_maybe_null())
+          key_part->key_part_flag|= HA_NULL_PART;
         /*
           Sometimes we can compare key parts for equality with memcmp.
           But not always.