Hi, Michael!

On Apr 16, Michael Widenius wrote:
> Hi!
>
> On Thu, Apr 16, 2020 at 1:17 PM Sergei Golubchik <serg@mariadb.org> wrote:
>
> <cut>
> > where's a test case for MDEV-22077?
>
> One can't use the test case in MDEV-22077 as it involves a table
> created by a 32 bit MariaDB version. Doing another test case it's very
> hard so I ignored it and just did run the test to verify the patch.

Alice posted a simple test case in the comments.
It has a very similar stack trace.
Could you check it out? Is it a same bug or a different one?

> > > diff --git a/sql/sql_delete.cc b/sql/sql_delete.cc
> > > index 19eabbb053c..2fc0de4345f 100644
> > > --- a/sql/sql_delete.cc
> > > +++ b/sql/sql_delete.cc
> > > @@ -547,10 +547,12 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
> > >      else
> > >      {
> > >        ha_rows scanned_limit= query_plan.scanned_rows;
> > > +      table->no_keyread= 1;
> > >        query_plan.index= get_index_for_order(order, table, select, limit,
> > >                                              &scanned_limit,
> > >                                              &query_plan.using_filesort,
> > >                                              &reverse);
> > > +      table->no_keyread= 0;
> >
> > why?
>
> get_index_for_order is not allowed to change to use key_reads as there
> is no guarantee
> at this point that the suggested index will be used. That was the
> reason we got crashes.

Why does it enable keyread then? Where?