Function join_tab_execution_startup

sql/opt_subselect.cc:5978–6029

*/

enum_nested_loop_state join_tab_execution_startup(JOIN_TAB *tab)
{
  Item_in_subselect *in_subs;
  DBUG_ENTER("join_tab_execution_startup");
  
  if (tab->table->pos_in_table_list && 
      (in_subs= tab->table->pos_in_table_list->jtbm_subselect))
  {
    /* It's a non-merged SJM nest */
    DBUG_ASSERT(in_subs->engine->engine_type() ==
                subselect_engine::HASH_SJ_ENGINE);
    subselect_hash_sj_engine *hash_sj_engine=
      ((subselect_hash_sj_engine*)in_subs->engine);
    if (!hash_sj_engine->is_materialized)
    {
      int error= hash_sj_engine->materialize_join->exec();
      hash_sj_engine->is_materialized= TRUE; 

      if (unlikely(error) ||
          unlikely(tab->join->thd->is_fatal_error))
        DBUG_RETURN(NESTED_LOOP_ERROR);
    }
  }
  else if (tab->bush_children)
  {
    /* It's a merged SJM nest */
    enum_nested_loop_state rc;
    SJ_MATERIALIZATION_INFO *sjm= tab->bush_children->start->emb_sj_nest->sj_mat_info;

    if (!sjm->materialized)
    {
      JOIN *join= tab->join;
      JOIN_TAB *join_tab= tab->bush_children->start;
      JOIN_TAB *save_return_tab= join->return_tab;
      /*
        Now run the join for the inner tables. The first call is to run the
        join, the second one is to signal EOF (this is essential for some
        join strategies, e.g. it will make join buffering flush the records)
      */
      if ((rc= sub_select(join, join_tab, FALSE/* no EOF */)) < 0 ||
          (rc= sub_select(join, join_tab, TRUE/* now EOF */)) < 0)
      {
        join->return_tab= save_return_tab;
        DBUG_RETURN(rc); /* it's NESTED_LOOP_(ERROR|KILLED)*/
      }
      join->return_tab= save_return_tab;
      sjm->materialized= TRUE;
    }
  }

  DBUG_RETURN(NESTED_LOOP_OK);
}


/*