Re: Multi-column distinctness.

On 20 October 2015 at 11:59, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > On Tue, Oct 20, 2015 at 10:51 AM, Tomas Vondra
> > <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
> >>>> ISTM that we could use COLLECT STATISTICS instead of ADD STATISTICS,
> and
> >>>> use REMOVE STATISTICS instead of DROP STATISTICS. That way we can use
> >>>> ALTER TABLE rather than inventing a new command. 5 minute change...
>
> >> That seems like a neat idea, actually. I'm not sure COLLECT is a good
> choice
> >> as it suggest the statistics is actually built, but that only happens
> during
> >> ANALYZE. But otherwise this seems to solve the issues with keywords and
> it's
> >> quite simple.
>
> > But ADD is no better there. I think ALTER TABLE .. COLLECT STATISTICS
> > isn't any worse than ALTER TABLE ... CLUSTER ON index_name. In both
> > cases, it means, when you do this operation, do it this way.
>
> > I would suggest that instead of DROP or REMOVE, the opposite should be
> > ALTER TABLE .. NO COLLECT STATISTICS.
>
> Why is this an improvement over using already-existing keywords?
>

The earlier patch changed the grammar for the DROP (column) subcommand,
which I am saying is not acceptable.

So by using an alternate keyword we are able to keep the existing syntax
untouched.

I suggested the word COLLECT since that is another word commonly used in
conjunction with STATISTICS (at least in DB2 and Teradata).

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