MDEV-13623 Assertion `!table || (!table->read_set || bitmap_is_set(table->read_set, field_index))' failed in virtual longlong Field_long::val_int

multi-update first runs a select to find affected rows, then performs
a separate update step. On the second step WITH CHECK OPTION rows
are read with rnd_read, but the first step might've been done with
keyread.

keyread over indexed virtual columns only reads the column's value, not
dependent base columns. This is reflected in the read_set too.  But on
the rnd_read step base columns must be read - thus we need to update the
read_set before doing updates.

Author: vuvova

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

@@ -155,3 +155,13 @@ select * from t;
 a	b	c	d	e
 11	11	11	11	11
 drop table t, t1, t2;
+create table t (f1 int, f2 int, f3 int as (f1*2) virtual, key(f3,f2));
+insert into t (f1,f2) values (1,1),(2,2);
+create view v as
+select a2.f1, a2.f2, a1.f3
+from t a1, t a2
+where a2.f3 <> 0
+with local check option;
+update v set f3 = 52;
+drop view v;
+drop table t;

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

@@ -111,3 +111,17 @@ check table t; select * from t;
 update t, t tt set t.b=11, tt.d=11 where t.a=tt.a;
 check table t; select * from t;
 drop table t, t1, t2;
+
+#
+# MDEV-13623 Assertion `!table || (!table->read_set || bitmap_is_set(table->read_set, field_index))' failed in virtual longlong Field_long::val_int
+#
+create table t (f1 int, f2 int, f3 int as (f1*2) virtual, key(f3,f2));
+insert into t (f1,f2) values (1,1),(2,2);
+create view v as
+  select a2.f1, a2.f2, a1.f3
+  from t a1, t a2
+  where a2.f3 <> 0
+  with local check option;
+update v set f3 = 52;
+drop view v;
+drop table t;

sql/sql_update.cc

@@ -2308,6 +2308,26 @@ int multi_update::do_updates()
   do_update= 0;					// Don't retry this function
   if (!found)
     DBUG_RETURN(0);
+
+  /*
+    Update read_set to include all fields that virtual columns may depend on.
+    Usually they're already in the read_set, but if the previous access
+    method was keyread, only the virtual column itself will be in read_set,
+    not its dependencies
+  */
+  while(TABLE *tbl= check_opt_it++)
+  {
+    if (tbl->vcol_set)
+    {
+      bitmap_clear_all(tbl->vcol_set);
+      for (Field **vf= tbl->vfield; *vf; vf++)
+      {
+        if (bitmap_is_set(tbl->read_set, (*vf)->field_index))
+          tbl->mark_virtual_col(*vf);
+      }
+    }
+  }
+
   for (cur_table= update_tables; cur_table; cur_table= cur_table->next_local)
   {
     bool can_compare_record;