Re: WIP: Covering + unique indexes.

On 2017-03-31 20:40:59 +0300, Anastasia Lubennikova wrote:
> 30.03.2017 22:11, Andres Freund
> > Any objection from reviewers to push both patches?
> 
> First of all, I want to thank you and Robert for reviewing this patch.
> Your expertise in postgres subsystems is really necessary for features like
> this.
> I just wonder, why don't you share your thoughts and doubts till the "last
> call".

Because there's a lot of other patches?  I only looked because Teodor
announced he was thinking about committing - I just don't have the
energy to look at all patches before they're ready to commit.
Unfortunatly "ready-for-committer" is very frequently not actually that
:(


> > Maybe it would be better to modify index_form_tuple() to accept a new
> > argument with a number of attributes, then you can just Assert that
> > this number is never higher than the number of attributes in the
> > TupleDesc.
> Good point.
> I agree that this function is a bit strange. I have to set
> tupdesc->nattrs to support compatibility with index_form_tuple().
> I didn't want to add neither a new field to tupledesc nor a new
> parameter to index_form_tuple(), because they are used widely.
> 
> 
> But I haven't considered the possibility of index_form_tuple() failure.
> Fixed in this version of the patch. Now it creates a copy of tupledesc to
> pass it to index_form_tuple.

That seems like it'd actually be a noticeable increase in memory
allocator overhead.  I think we should just add (as just proposed in
separate thread), a _extended version of it that allows to specify the
number of columns.

- Andres