Re: [patch] Proposal for \crosstabview in psql

Hi!

Interesting feature, but it's not very obvious how to use it. I'd like to see 
some example(s) in documentation.

And I see an implementation of AVL tree in psql source code 
(src/bin/psql/crosstabview.c). Postgres already has a Red-Black tree 
implementation in
src/include/lib/rbtree.h and src/backend/lib/rbtree.c. Is any advantage of using 
AVL tree here? I have some doubt about that and this implementation, obviously, 
will not be well tested. But I see in comments that implementation is reduced to 
insert only and it doesn't use the fact of ordering tree, so, even hash could be 
used.

Daniel Verite wrote:
>     Pavel Stehule wrote:
>
>> 1. maybe we can decrease name to shorter "crossview" ?? I am happy with
>> crosstabview too, just crossview is correct too, and shorter
>
> I'm in favor of keeping crosstabview. It's more explicit, only
> 3 characters longer and we have tab completion anyway.
>
>> 2. Columns used for ordering should not be displayed by default. I can live
>> with current behave, but hiding ordering columns is much more practical for
>> me
>
> I can see why, but I'm concerned about a consequence:
> say we have 4 columns A,B,C,D and user does \crosstabview +A:B +C:D
> If B and D are excluded by default, then there's nothing
> left to display inside the grid.
> It doesn't feel quite right. There's something counter-intuitive
> in the fact that values in the grid would disappear depending on
> whether and how headers are sorted.
> With the 3rd argument, we let the user decide what they want
> to see.
>
>> 3. This code is longer, so some regress tests are recommended - attached
>> simple test case
>
> I've added a few regression tests to the psql testsuite
> based on your sample data. New patch with these tests
> included is attached, make check passes.
>
> Best regards,
>
>
>
>

-- 
Teodor Sigaev                                   E-mail: teodor@sigaev.ru
  WWW: http://www.sigaev.ru/