Bug#43737: Select query return bad result

      
A bug in the initialization of key segment information made it point
to the wrong bit, since a bit index was used when its int value
was needed. This lead to misinterpretation of bit columns
read from MyISAM record format when a NULL bit pushed them over
a byte boundary.
Fixed by using the int value of the bit instead.

mysql-test/r/myisam.result

@@ -2226,4 +2226,30 @@ Key Start Len Index   Type
 1   2     30  multip. varchar              
 2   33    30  multip. char NULL            
 DROP TABLE t1;
+CREATE TABLE t1 (
+c INT,
+d bit(1),
+e INT,
+f VARCHAR(1),
+g BIT(1),
+h BIT(1),
+KEY (h, d, e, g)
+);
+INSERT INTO t1 VALUES
+(  3, 1, 1, 'a', 0, 0 ),
+(  3, 1, 5, 'a', 0, 0 ),
+( 10, 1, 2, 'a', 0, 1 ),
+( 10, 1, 3, 'a', 0, 1 ),
+( 10, 1, 4, 'a', 0, 1 );
+SELECT f FROM t1 WHERE d = 1 AND e = 2 AND g = 0 AND h = 1;
+f
+a
+SELECT h+0, d + 0, e, g + 0 FROM t1;
+h+0	d + 0	e	g + 0
+0	1	1	0
+0	1	5	0
+1	1	2	0
+1	1	3	0
+1	1	4	0
+DROP TABLE t1;
 End of 5.1 tests

mysql-test/t/myisam.test

@@ -1478,5 +1478,30 @@ let $MYSQLD_DATADIR= `select @@datadir`;
 --exec $MYISAMCHK -d $MYSQLD_DATADIR/test/t1
 DROP TABLE t1;
 
+#
+# Bug#43737: Select query return bad result
+#
+CREATE TABLE t1 (
+  c INT,
+  d bit(1),
+  e INT,
+  f VARCHAR(1),
+  g BIT(1),
+  h BIT(1),
+  KEY (h, d, e, g)
+);
+INSERT INTO t1 VALUES
+  (  3, 1, 1, 'a', 0, 0 ),
+  (  3, 1, 5, 'a', 0, 0 ),
+  ( 10, 1, 2, 'a', 0, 1 ),
+  ( 10, 1, 3, 'a', 0, 1 ),
+  ( 10, 1, 4, 'a', 0, 1 );
+
+SELECT f FROM t1 WHERE d = 1 AND e = 2 AND g = 0 AND h = 1;
+
+SELECT h+0, d + 0, e, g + 0 FROM t1;
+
+DROP TABLE t1;
+
 --echo End of 5.1 tests
 

storage/myisam/mi_open.c

@@ -1160,7 +1160,8 @@ uchar *mi_keyseg_read(uchar *ptr, HA_KEYSEG *keyseg)
    keyseg->null_pos	= mi_uint4korr(ptr);  ptr +=4;
    keyseg->charset=0;				/* Will be filled in later */
    if (keyseg->null_bit)
-     keyseg->bit_pos= (uint16)(keyseg->null_pos + (keyseg->null_bit == 7));
+     /* We adjust bit_pos if null_bit is last in the byte */
+     keyseg->bit_pos= (uint16)(keyseg->null_pos + (keyseg->null_bit == (1 << 7)));
    else
    {
      keyseg->bit_pos= (uint16)keyseg->null_pos;