MDEV-11750 Assertion `vfield' failed in TABLE::update_virtual_fields after...

MDEV-11750 Assertion `vfield' failed in TABLE::update_virtual_fields after crash recovery on corrupted MyISAM table

Adjust the length of the BIT field
(same as in _mi_put_key_in_record())

mysql-test/suite/vcol/r/vcol_keys_myisam.result

@@ -365,3 +365,13 @@ ALTER TABLE t1 ADD INDEX(col_enum,vcol_int);
 SET STATEMENT sql_mode = 'NO_ENGINE_SUBSTITUTION' FOR
 ALTER TABLE t1 ADD INDEX(col_year);
 DROP TABLE t1;
+create table t1 (
+pk int primary key auto_increment,
+b bit default null,
+key(b)
+) engine=myisam;
+insert into t1 values (null, 0);
+repair table t1 extended;
+Table	Op	Msg_type	Msg_text
+test.t1	repair	status	OK
+drop table t1;

mysql-test/suite/vcol/t/vcol_keys_myisam.test

@@ -249,3 +249,16 @@ SET STATEMENT sql_mode = 'NO_ENGINE_SUBSTITUTION' FOR
 ALTER TABLE t1 ADD INDEX(col_year);
 --enable_warnings
 DROP TABLE t1;
+
+#
+# MDEV-11750 Assertion `vfield' failed in TABLE::update_virtual_fields after crash recovery on corrupted MyISAM table
+#
+create table t1 (
+  pk int primary key auto_increment,
+  b bit default null,
+  key(b)
+) engine=myisam;
+
+insert into t1 values (null, 0);
+repair table t1 extended;
+drop table t1;

storage/myisam/mi_open.c

@@ -376,6 +376,8 @@ MI_INFO *mi_open(const char *name, int mode, uint open_flags)
           {
             uint real_length= pos->flag & HA_BLOB_PART ? pos->bit_start
                                                        : pos->length;
+            if (pos->type == HA_KEYTYPE_BIT && pos->bit_length)
+              real_length--;
             set_if_bigger(share->vreclength, pos->start + real_length);
           }
 	}