Hi Serg!
On Tue, Mar 26, 2019 at 10:48 PM Sergei Golubchik <s...@mariadb.org> wrote:
>
> Hi, Aleksey!
>
> On Mar 26, Aleksey Midenkov wrote:
> > revision-id: 74b2eba1ca6 (mariadb-10.3.12-115-g74b2eba1ca6)
> > parent(s): 2c0901d808b
> > author: Aleksey Midenkov <mide...@gmail.com>
> > committer: Sergei Golubchik <s...@mariadb.com>
> > timestamp: 2019-03-26 17:43:38 +0100
> > message:
> >
> > MDEV-15458 Segfault in heap_scan() upon UPDATE after ADD SYSTEM VERSIONING
> >
> > * HA_EXTRA_REMEMBER_POS, HA_EXTRA_RESTORE_POS for HEAP storage engine
> > * Versioning tests support
> >
> > diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc
> > index abe4254db3e..1d51947cc86 100644
> > --- a/sql/sql_insert.cc
> > +++ b/sql/sql_insert.cc
> > @@ -1643,7 +1643,12 @@ int vers_insert_history_row(TABLE *table)
> >    if (row_start->cmp(row_start->ptr, row_end->ptr) >= 0)
> >      return 0;
> >
> > -  return table->file->ha_write_row(table->record[0]);
> > +  int res;
> > +  if ((res= table->file->extra(HA_EXTRA_REMEMBER_POS)))
> > +    return res;
> > +  if ((res= table->file->ha_write_row(table->record[0])))
> > +    return res;
> > +  return table->file->extra(HA_EXTRA_RESTORE_POS);
> >  }
>
> Frankly, I don't like it. I mean, this particular fix is fine, but
> here's the problem:
>
> We now have (at least) three features where the server might need to do
> something (insert/update/search) during the index/rnd scan.
>
> And three different solutions: you use HA_EXTRA_REMEMBER_POS in system
> versioning, Nikita simply sets delete_while_scanning=false in
> application time period tables, and Sachin uses handler::clone() to
> create a second handler that can be used to check for hash collisions
> without disrupting the scan on the primary handler.
Actually I liked the Aleksey approach it is much easier then cloning
and I don't have  to free handler in close table
Although I tried with long unique update I was getting assert fail in
ha_index_read_map
  DBUG_ASSERT(inited==INDEX);
Can we do (different )index scan after
table->file->extra(HA_EXTRA_REMEMBER_POS) ?
>
> I think it's getting somewhat out of hands. Can we please reduce the
> number of approaches to fix the same issue?
>
> Regards,
> Sergei
> Chief Architect MariaDB
> and secur...@mariadb.org
>
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