Re: ALTER TABLE .. ALTER COLUMN .. ERROR: attribute .. has wrong type

Tom Lane wrote:
> Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> > Tom Lane wrote:
> >> [ pokes around... ] The code I was thinking of is convert_tuples_by_name
> >> in access/common/tupconvert.c. There's a bit of an API mismatch in that
> >> it wants to wrap the mapping array in a TupleConversionMap struct; but
> >> maybe we could refactor tupconvert.c to offer a way to get just the map
> >> array.
>
> > Ah, nice gadget. I think the attached patch should do.
>
> Looks reasonable to me.

Thanks for looking! Pushed.

> > Hm, I was thinking in unreasonable numbers of columns, keeping in mind
> > that they can appear in arbitrary order in child tables. Then again,
> > that probably seldom occurs in real databases. I suppose this could
> > become an issue with table partitioning becoming more common, but I'm
> > okay with deferring the optimization work.
>
> It occurred to me that it'd be really easy to improve
> convert_tuples_by_name so that, rather than having the inner loop
> start from j = 0 every time, it starts from the attribute after the
> last match (and loops around if needed, so that it still examines
> every child attribute). I think this would keep it at more-or-less
> linear time for all but very contrived child tables.
>
> Since your patch is touching that code I won't do anything about it
> right now, but maybe later.

Yeah, I had the same idea. Looks fiddly but not terribly difficult, and
well localized. Didn't we have a list of tasks for eager contributors?

--
Álvaro Herrera https://www.2ndQuadrant.com/
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