PostgreSQL在何处处理 sql查询之二十四

接前面，回到 get_relation_info(plancat.c)函数 上：

relation 是由 heap_open 函数调用后获得的。

void
get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
                  RelOptInfo *rel)
{
    Index        varno = rel->relid;
    Relation    relation;
    bool        hasindex;
    List       *indexinfos = NIL;

    /*
     * We need not lock the relation since it was already locked, either by
     * the rewriter or when expand_inherited_rtentry() added it to the query's
     * rangetable.
     */
    relation = heap_open(relationObjectId, NoLock);

    ...
    /*
     * Estimate relation size --- unless it's an inheritance parent, in which
     * case the size will be computed later in set_append_rel_pathlist, and we
     * must leave it zero for now to avoid bollixing the total_table_pages
     * calculation.
     */
    if (!inhparent)
        estimate_rel_size(relation, rel->attr_widths - rel->min_attr,
                          &rel->pages, &rel->tuples, &rel->allvisfrac);

    ...
}

经过验证，heap_open后，就把relation的一些信息准备好了。

其中包括  relation->rd_rel->reltuples。

仍然回到  此get_relation_info函数中，当我访问表 tst01时（其对应文件为 16384）,

我可以看到入口参数的 oid正好是  16384。