Re: Retrieving Alias Name

On Tue, Feb 26, 2019 at 10:48 PM Walter Cai <walter(at)cs(dot)washington(dot)edu> wrote:
>
> I'm currently using a (very rough) scheme to retrieve relation names from a PlannerInfo, and a RelOptInfo struct:
>
> PlannerInfo *root
> RelOptInfo *inner_rel
>
> //...
>
> RangeTblEntry *rte;
> int x = -1;
> while ((x = bms_next_member(inner_rel->relids, x)) >= 0)
> {
> rte = root->simple_rte_array[x];
> if (rte->rtekind == RTE_RELATION)
> {
> char *rel_name = get_rel_name(rte->relid);
> // do stuff...
> }
> }
>
> However, I now realize it would be better to access aliases as they appear in the SQL query. For instance, if the query contains "... FROM rel_name AS rel_alias ..." I would like to retrieve `rel_alias` instead of `rel_name`.
>
> Is it possible to derive the alias in a similar way?

You can use rte->eref->aliasname, which will contain the alias is one
was provided, otherwise the original name. You can see RangeTblEntry
comment in include/nodes/parsenodes.h for more details.