Re: proposal psql \gdesc

2017-05-09 23:00 GMT+02:00 Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>:

>
> What about detecting the empty result (eg PQntuples()==0?) and writing
>>> "Empty result" instead of the strange looking empty table above? That
>>> would
>>> just mean skipping the PrintQueryResult call in this case?
>>>
>>
>> PQntuples == 0 every time - the query is not executed.
>>
>
> I meant to test the query which collects type names, which is executed?
>

How it can help?

>
> Or check that PQnfields() == 0 on the PQdescribePrepared() result, so that
> there is no need to execute the type name collection query?
>
> For the case "SELECT;" the empty table is correct.
>>
>
> Ok. Then write "Empty table"?
>
> For TRUNCATE and similar command I am not sure. The empty table is maybe
>> unusual, but it is valid - like "SELECT;".
>>
>
> I would partly disagree:
>
> "SELECT;" does indeed return an empty relation, so I agree that an empty
> table is valid whether spelled out as "Empty table" or explicitly.
>
> However, ISTM that "TRUNCATE stuff;" does *NOT* return a relation, so
> maybe "No table" would be ok, but not an empty table... ?!
>
> So I could be okay with both:
>
> SELECT \gdesc
> -- "Empty table" or some other string
> Or
> -- Name | Type
>
> Although I prefer the first one, because the second looks like a bug
> somehow: I asked for a description, but nothing is described... even if the
> answer is somehow valid, it looks pretty strange.
>
> The same results do not realy suit "TRUNCATE Foo \gdesc", where "No table"
> would seem more appropriate?
>
> In both case, "Empty result" is kind of neutral, it does not promise a
> table or not. Hmmm. At least not too much. Or maybe some other string such
> as "Nothing" or "No result"?
>
> Now I wonder whether the No vs Empty cases can be distinguished?

No with standard libpq API :(

I am sending a variant with message instead empty result.

Personally I prefer empty result instead message. It is hard to choose some
good text of this message. Empty result is just empty result for all cases.

Regards

Pavel

>
> --
> Fabien.
>