MDEV-22973 Assertion in compare_record upon multi-update involving versioned table via view

records_are_comparable() requires this condition:

  bitmap_is_subset(table->write_set, table->read_set)

On first iteration vers_update_fields() changes write_set and
read_set. On second iteration the above condition fails.

Added missing read bit for ROW_START. Also reorganized
bitmap_set_bit() so it is called only when needed.

mysql-test/suite/versioning/r/update.result

@@ -410,3 +410,14 @@ select check_row_ts(row_start, row_end) from t1 for system_time all where row_st
 check_row_ts(row_start, row_end)
 CURRENT ROW
 drop table t1;
+#
+# MDEV-22973 Assertion in compare_record upon multi-update involving versioned table via view
+#
+create or replace table t1 (a int, primary key (a)) engine=myisam;
+insert into t1 values (0);
+create or replace table t2 (pk int, b int, primary key (pk), key(b)) engine=innodb with system versioning;
+insert into t2 values (1, 0), (2, 0);
+create or replace view v as select a, b from t1, t2;
+update v set b= null where a = 0 order by b;
+drop view v;
+drop table t1, t2;

mysql-test/suite/versioning/t/update.test

@@ -336,4 +336,17 @@ select row_start from t1 into @r;
 select check_row_ts(row_start, row_end) from t1 for system_time all where row_start = @r;
 drop table t1;
 
+--echo #
+--echo # MDEV-22973 Assertion in compare_record upon multi-update involving versioned table via view
+--echo #
+create or replace table t1 (a int, primary key (a)) engine=myisam;
+insert into t1 values (0);
+create or replace table t2 (pk int, b int, primary key (pk), key(b)) engine=innodb with system versioning;
+insert into t2 values (1, 0), (2, 0);
+create or replace view v as select a, b from t1, t2; 
+update v set b= null where a = 0 order by b;
+# cleanup
+drop view v;
+drop table t1, t2;
+
 source suite/versioning/common_finish.inc;

sql/table.cc

@@ -8161,9 +8161,6 @@ void TABLE::evaluate_update_default_function()
 
 void TABLE::vers_update_fields()
 {
-  bitmap_set_bit(write_set, vers_start_field()->field_index);
-  bitmap_set_bit(write_set, vers_end_field()->field_index);
-
   if (!vers_write)
   {
     file->column_bitmaps_signal();
@@ -8172,17 +8169,21 @@ void TABLE::vers_update_fields()
 
   if (versioned(VERS_TIMESTAMP))
   {
+    bitmap_set_bit(write_set, vers_start_field()->field_index);
     if (vers_start_field()->store_timestamp(in_use->query_start(),
                                           in_use->query_start_sec_part()))
     {
       DBUG_ASSERT(0);
     }
     vers_start_field()->set_has_explicit_value();
+    bitmap_set_bit(read_set, vers_start_field()->field_index);
   }
 
+  bitmap_set_bit(write_set, vers_end_field()->field_index);
   vers_end_field()->set_max();
   vers_end_field()->set_has_explicit_value();
   bitmap_set_bit(read_set, vers_end_field()->field_index);
+
   file->column_bitmaps_signal();
   if (vfield)
     update_virtual_fields(file, VCOL_UPDATE_FOR_READ);