On Fri, Oct 26, 2018 at 1:12 PM Amit Langote
<Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote:
>
> On 2018/10/25 19:54, Dilip Kumar wrote:
> > On Mon, Oct 22, 2018 at 7:47 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> Amit Langote <amitlangote09(at)gmail(dot)com> writes:
> >>> But maybe for the case under question, that's irrelevant, because
> >>> we're only interested in access to inherited columns as those are the
> >>> only ones that can be accessed in queries via parent.
> >>
> >> Yeah, that's what I thought. It seems like it should be possible to base
> >> all stats access decisions off the table actually named in the query,
> >> because only columns appearing in that table could be referenced, and only
> >> that table's permissions actually get checked at runtime.
> >>
> >> I guess it's possible that a child table could have, say, an index on
> >> column X (inherited) and column Y (local) and that some aspect of costing
> >> might then be interested in the behavior of column Y, even though the
> >> query could only mention X not Y. But then we could fall back to the
> >> existing behavior.
> >
> > Basically, if the relation is RELOPT_OTHER_MEMBER_REL, we can
> > recursively fetch its parent until we reach to the base relation
> > (which is actually named in the query). And, once we have the base
> > relation we can check ACL on that and set vardata->acl_ok accordingly.
> > Additionally, for getting the parent RTI we need to traverse
> > "root->append_rel_list". Another alternative could be that we can add
> > parent_rti member in RelOptInfo structure.
>
> Adding parent_rti would be a better idea [1]. I think that traversing
> append_rel_list every time would be inefficient.
> [1] I've named it inh_root_parent in one of the patches I'm working on
> where I needed such a field (https://commitfest.postgresql.org/20/1778/)
Ok, Make sense. I have written a patch by adding this variable.
There is still one FIXME in the patch, basically, after getting the
baserel rte I need to convert child varattno to parent varattno
because in case of inheritance that can be different. Do we already
have any mapping from child attno to parent attno or we have to look
up the cache.
--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com