Re: proposal psql \gdesc

2017-05-09 18:15 GMT+02:00 Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>:

>
> Hello Pavel,
>
> Patch applies cleanly and compiles.
>>>
>>
> Idem for v2. "make check" ok. Tests look good.
>
> I would suggest some rewording, maybe:
>>>
>>> "Show the description of the result of the current query buffer without
>>> actually executing it, by considering it a prepared statement."
>>>
>>> done
>>
>
> Ok. If some native English speaker can clarify the sentence further, or
> imprive it anyway, thanks in advance!
>
> SELECT $1 AS unknown_type \gdesc
>>>
>>
>> It is not unknown type - the default placeholder type is text
>>
>
> Indeed. I really meant something like:
>
> calvin=# SELECT $1 + $2 \gdesc
> ERROR: operator is not unique: unknown + unknown
> ...
>
> More comments:
>
> I propose that the help message could be "describe result of query without
> executing it".
>

done

>
> I found an issue. \gdesk fails when the command does not return a result:
>
> calvin=# TRUNCATE pgbench_history \gdesc
> ERROR: syntax error at or near ")"
> LINE 2: (VALUES ) s (name, tp, tpm)
>
> I guess the issue is that PQdescribePrepared returns an empty description,
> which is fine, but then the second query should be skipped, and some
> message should be output instead, like "no result" or whatever...
>
> This need fixing, and a corresponding test should be added.
>

it is little bit worse. I cannot to distinguish between SELECT\gdesc and
TRUNCATE xxx\gdesc . All are valid commands and produce empty result, so
result of \gdesc command should be empty result too.

postgres=# truncate table xx\gdesc
┌──────┬──────┐
│ Name │ Type │
╞══════╪══════╡
└──────┴──────┘
(0 rows)

postgres=# select \gdesc
┌──────┬──────┐
│ Name │ Type │
╞══════╪══════╡
└──────┴──────┘
(0 rows)

> Also I would suggest to add a \g after the first test, which would execute
> the current buffer after its description, to show that the current buffer
> does indeed hold the query:
>
> calvin=# SELECT 1 as one, ... \gdesc \g
> -- one | int
> -- ...
> -- 1 | ...
>
>
done

Regards

Pavel

> --
> Fabien.
>