PostgreSQL在何处处理 sql查询之六十二

对

RelOptInfo *
make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2) 函数进行研究：

看看 inner join 时候发生的事情：

RelOptInfo *
make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
{
   ...
   SpecialJoinInfo *sjinfo;
   ...
   /* Check validity and determine join type. */
   if (!join_is_legal(root, rel1, rel2, joinrelids,
                      &sjinfo, &reversed))
   ...
   /*
    * If it's a plain inner join, then we won't have found anything in
    * join_info_list.    Make up a SpecialJoinInfo so that selectivity
    * estimation functions will know what's being joined.
    */
   if (sjinfo == NULL)
   {
        sjinfo = &sjinfo_data;
        sjinfo->type = T_SpecialJoinInfo;
        sjinfo->min_lefthand = rel1->relids;
        sjinfo->min_righthand = rel2->relids;
        sjinfo->syn_lefthand = rel1->relids;
        sjinfo->syn_righthand = rel2->relids;
        sjinfo->jointype = JOIN_INNER;
        /* we don't bother trying to make the remaining fields valid */
        sjinfo->lhs_strict = false;
        sjinfo->delay_upper_joins = false;
        sjinfo->join_quals = NIL;
   }
   ...
   switch (sjinfo->jointype)
   {
        case JOIN_INNER:

            fprintf(stderr,"JOIN_INNER \n");

            if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
                restriction_is_constant_false(restrictlist, false))
            {
                mark_dummy_rel(joinrel);
                break;
            }
            add_paths_to_joinrel(root, joinrel, rel1, rel2,
                                 JOIN_INNER, sjinfo,
                                 restrictlist);
            add_paths_to_joinrel(root, joinrel, rel2, rel1,
                                 JOIN_INNER, sjinfo,
                                 restrictlist);
            break;
         ...
   }
   ...
}