Re: [patch] Proposal for \rotate in psql - Mailing list pgsql-hackers

        Pavel Stehule wrote:

> I am looking on this last patch. I talked about the name of this command
> with more people, and the name "rotate" is unhappy. The correct name for
> this visualization technique is "crosstab" (see google "crosstab"). The
> conflict with our extension is unhappy, but using "rotate" is more worst -
> (see google "rotate"). The term "rotate" is used less time (related to
> topic), and usually with zero informed people. More, in attached doc, the
> word "crosstab" is pretty often used, and then the word "rotate" has not
> sense.

First, thanks for looking again at the patch and for your feedback.

I note that you dislike and oppose the current name, as previously
when that choice of name was discussed quite a bit.
However I disagree that "rotate" doesn't make sense. On the semantics
side, several people have expressed upthread that it was OK, as a
plausible synonym for  "pivot". If it's unencumbered by previous use
in this context, then all the better, I'd say why not corner it for our
own use?
It's not as if we had to cling to others people choices for psql
meta-commands.

Anyway that's just a name. It shall be changed eventually to
whatever the consensus is, if one happens to emerge.

> The important question is sorting output. The vertical header is
> sorted by first appearance in result. The horizontal header is
> sorted in ascending or descending order. This is unfriendly for
> often use case - month names. This can be solved by third parameter
> - sort function.

Right, it's not possible currently to sort the horizontal header by
something else than the values in it.
I agree that it would be best to allow it if there's a reasonable way to
implement it. I'm not sure about letting the user provide a function
in argument.
In the case of the month names example, the function
f(monthname)=number-of-month may not exist. If the
user has to create it beforehand, it feels a bit demanding
for a display feature.

I wonder if this ordering information could be instead deduced
somehow from the non-pivoted resultset at a lower cost.
I'll try to think more and experiment around this.

Best regards,
--
Daniel Vérité
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