Fix for BUG#5401 (attempt 2)

innobase/row/row0sel.c:
  Fix for BUG#5401: Don't reset the entire NULL mask, only set/clear bits for particular fields.
    This is necessary because index_merge ROR-intersection uses simulatenous scans on several keys
    with the same row buffer.
mysql-test/r/index_merge_innodb.result:
  Test for BUG#5401
mysql-test/t/index_merge_innodb.test:
  Test for BUG#5401

innobase/row/row0sel.c

@@ -2331,11 +2331,6 @@ row_sel_store_mysql_rec(
 		prebuilt->blob_heap = NULL;
 	}
 
-	/* MySQL assumes that all columns have the SQL NULL bit set unless it
-	is a nullable column with a non-NULL value */
-
-	memset(mysql_rec, 0xFF, prebuilt->null_bitmap_len);
-
 	for (i = 0; i < prebuilt->n_template; i++) {
 
 		templ = prebuilt->mysql_template + i;
@@ -2431,6 +2426,8 @@ row_sel_store_mysql_rec(
 		        bug number 154 in the MySQL bug database: GROUP BY
 		        and DISTINCT could treat NULL values inequal. */
 
+			mysql_rec[templ->mysql_null_byte_offset] |=
+					(byte) (templ->mysql_null_bit_mask);
 			if (templ->type == DATA_VARCHAR
 			    || templ->type == DATA_CHAR
 			    || templ->type == DATA_BINARY
@@ -2734,6 +2731,7 @@ row_sel_pop_cached_row_for_mysql(
 	ulint			i;
 	mysql_row_templ_t*	templ;
 	byte*			cached_rec;
+        byte			null_byte;
         ut_ad(prebuilt->n_fetch_cached > 0);
 	
 	if (prebuilt->keep_other_fields_on_keyread)
@@ -2749,10 +2747,16 @@ row_sel_pop_cached_row_for_mysql(
 				buf + templ->mysql_col_offset, 
 				cached_rec + templ->mysql_col_offset,
 				templ->mysql_col_len);
-
+                        /* Copy NULL bit of the current field from cached_rec 
+			to buf */
 			if (templ->mysql_null_bit_mask)
-				buf[templ->mysql_null_byte_offset] &= 
+			{
+				null_byte = buf[templ->mysql_null_byte_offset] & 
+					~(byte)templ->mysql_null_bit_mask;
+				null_byte |= (byte)templ->mysql_null_bit_mask & 
 					cached_rec[templ->mysql_null_byte_offset];
+				buf[templ->mysql_null_byte_offset] = null_byte;
+			}
 		}
 	}
 	else

mysql-test/r/index_merge_innodb.result

@@ -53,3 +53,71 @@ key1	key2	str1	zeroval	str2	str3
 1	199	aaa	0	bbb	199-0_A
 0	200	aaa	0	bbb	200-0_a
 drop table t1;
+create table t1 (
+pk    integer not null auto_increment primary key,
+key1  integer,
+key2  integer not null,
+filler char  (200),
+index (key1),
+index (key2)
+) engine=innodb;
+show warnings;
+Level	Code	Message
+explain select pk from t1 where key1 = 1 and key2 = 1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index_merge	key1,key2	key1,key2	5,4	NULL	1	Using intersect(key1,key2); Using where; Using index
+select pk from t1 where key2 = 1 and key1 = 1;
+pk
+26
+select pk from t1 ignore index(key1,key2) where key2 = 1 and key1 = 1;
+pk
+26
+drop table t1;
+create table t1 (
+pk int primary key auto_increment,
+key1a  int,
+key2a  int,
+key1b  int,
+key2b  int,
+dummy1 int,
+dummy2 int,
+dummy3 int,
+dummy4 int,
+key3a  int,
+key3b  int,
+filler1 char (200),
+index i1(key1a, key1b),
+index i2(key2a, key2b),
+index i3(key3a, key3b)
+) engine=innodb;
+create table t2 (a int);
+insert into t2 values (0),(1),(2),(3),(4),(NULL);
+insert into t1 (key1a, key1b, key2a, key2b, key3a, key3b) 
+select A.a, B.a, C.a, D.a, C.a, D.a from t2 A,t2 B,t2 C, t2 D;
+insert into t1 (key1a, key1b, key2a, key2b, key3a, key3b) 
+select key1a, key1b, key2a, key2b, key3a, key3b from t1;
+insert into t1 (key1a, key1b, key2a, key2b, key3a, key3b) 
+select key1a, key1b, key2a, key2b, key3a, key3b from t1;
+analyze table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	OK
+select count(*) from t1;
+count(*)
+5184
+explain select count(*) from t1 where 
+key1a = 2 and key1b is null and  key2a = 2 and key2b is null;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index_merge	i1,i2	i1,i2	10,10	NULL	3	Using intersect(i1,i2); Using where; Using index
+select count(*) from t1 where 
+key1a = 2 and key1b is null and key2a = 2 and key2b is null;
+count(*)
+4
+explain select count(*) from t1 where 
+key1a = 2 and key1b is null and key3a = 2 and key3b is null;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index_merge	i1,i3	i1,i3	10,10	NULL	3	Using intersect(i1,i3); Using where; Using index
+select count(*) from t1 where 
+key1a = 2 and key1b is null and key3a = 2 and key3b is null;
+count(*)
+4
+drop table t1,t2;

mysql-test/t/index_merge_innodb.test

@@ -51,4 +51,72 @@ select * from t1 where key1 < 5 or key2 > 197;
 explain select * from t1 where key1 < 3 or key2 > 195;
 select * from t1 where key1 < 3 or key2 > 195;
 
+# Test for BUG#5401
 drop table t1;
+create table t1 (
+  pk    integer not null auto_increment primary key,
+  key1  integer,
+  key2  integer not null,
+  filler char  (200),
+  index (key1),
+  index (key2)
+) engine=innodb;
+show warnings;
+--disable_query_log
+let $1=30;
+while ($1)
+{
+  eval insert into t1 (key1, key2, filler) values ($1/4, $1/8, 'filler-data');
+  dec $1;
+}
+--enable_query_log
+explain select pk from t1 where key1 = 1 and key2 = 1;
+select pk from t1 where key2 = 1 and key1 = 1;
+select pk from t1 ignore index(key1,key2) where key2 = 1 and key1 = 1;
+
+# More tests for BUG#5401. 
+drop table t1;
+create table t1 (
+  pk int primary key auto_increment,
+  key1a  int,
+  key2a  int,
+  key1b  int,
+  key2b  int,
+  dummy1 int,
+  dummy2 int,
+  dummy3 int,
+  dummy4 int,
+  key3a  int,
+  key3b  int,
+  filler1 char (200),
+  index i1(key1a, key1b),
+  index i2(key2a, key2b),
+  index i3(key3a, key3b)
+) engine=innodb;
+
+create table t2 (a int);
+insert into t2 values (0),(1),(2),(3),(4),(NULL);
+
+insert into t1 (key1a, key1b, key2a, key2b, key3a, key3b) 
+  select A.a, B.a, C.a, D.a, C.a, D.a from t2 A,t2 B,t2 C, t2 D;
+insert into t1 (key1a, key1b, key2a, key2b, key3a, key3b) 
+  select key1a, key1b, key2a, key2b, key3a, key3b from t1;
+insert into t1 (key1a, key1b, key2a, key2b, key3a, key3b) 
+  select key1a, key1b, key2a, key2b, key3a, key3b from t1;
+analyze table t1;
+select count(*) from t1;
+
+explain select count(*) from t1 where 
+  key1a = 2 and key1b is null and  key2a = 2 and key2b is null;
+
+select count(*) from t1 where 
+  key1a = 2 and key1b is null and key2a = 2 and key2b is null;
+
+explain select count(*) from t1 where 
+  key1a = 2 and key1b is null and key3a = 2 and key3b is null;
+
+select count(*) from t1 where 
+  key1a = 2 and key1b is null and key3a = 2 and key3b is null;
+
+drop table t1,t2;
+