MDEV-15458 Segfault in heap_scan() upon UPDATE after ADD SYSTEM VERSIONING

handler::write_row() should not destroy the state of the running
index_search/index_next/... or rnd_init/rnd_next/... scan

sql/sql_delete.cc

@@ -254,12 +254,7 @@ int TABLE::delete_row()
 
   store_record(this, record[1]);
   vers_update_end();
-  int res;
-  if ((res= file->extra(HA_EXTRA_REMEMBER_POS)))
-    return res;
-  if ((res= file->ha_update_row(record[1], record[0])))
-    return res;
-  return file->extra(HA_EXTRA_RESTORE_POS);
+  return file->ha_update_row(record[1], record[0]);
 }
 
 

storage/heap/hp_write.c

@@ -58,8 +58,6 @@ int heap_write(HP_INFO *info, const uchar *record)
   if (++share->records == share->blength)
     share->blength+= share->blength;
   info->s->key_version++;
-  info->current_ptr=pos;
-  info->current_hash_ptr=0;
   info->update|=HA_STATE_AKTIV;
 #if !defined(DBUG_OFF) && defined(EXTRA_HEAP_DEBUG)
   DBUG_EXECUTE("check_heap",heap_check_heap(info, 0););

storage/maria/ma_write.c

@@ -88,7 +88,7 @@ int maria_write(MARIA_HA *info, uchar *record)
   MARIA_SHARE *share= info->s;
   uint i;
   int save_errno;
-  MARIA_RECORD_POS filepos;
+  MARIA_RECORD_POS filepos, oldpos= info->cur_row.lastpos;
   uchar *buff;
   my_bool lock_tree= share->lock_key_trees;
   my_bool fatal_error;
@@ -302,7 +302,7 @@ int maria_write(MARIA_HA *info, uchar *record)
   share->state.changed|= STATE_NOT_MOVABLE | STATE_NOT_ZEROFILLED;
   info->state->changed= 1;
 
-  info->cur_row.lastpos= filepos;
+  info->cur_row.lastpos= oldpos;
   _ma_writeinfo(info, WRITEINFO_UPDATE_KEYFILE);
   if (info->invalidator != 0)
   {

storage/myisam/mi_write.c

@@ -153,7 +153,6 @@ int mi_write(MI_INFO *info, uchar *record)
   info->update= (HA_STATE_CHANGED | HA_STATE_AKTIV | HA_STATE_WRITTEN |
 		 HA_STATE_ROW_CHANGED);
   info->state->records++;
-  info->lastpos=filepos;
   myisam_log_record(MI_LOG_WRITE,info,record,filepos,0);
   (void) _mi_writeinfo(info, WRITEINFO_UPDATE_KEYFILE);
   if (info->invalidator != 0)