Обсуждение: My second PL/pgSQL function - minor problem

Hey all,

http://pastebin.com/f1015226d

The above function appears to be doing exactly what I want: Fetch the users data and update the visits column, if the supplied credentials match a user.

My problem is what happens when the credentials don't match a user. In those cases I would like to have a boolean false returned, but instead I get an empty array - which of course is entirely according to the functions "RETURN SETOF users" statement.

Is this little problem solvable, or will I have to learn to live with the empty array?

Regards,
Thomas

In response to Thomas Løcke :
> Hey all,
>
> http://pastebin.com/f1015226d
>
> The above function appears to be doing exactly what I want: Fetch the users
> data and update the visits column, if the supplied credentials match a user.
>
> My problem is what happens when the credentials don't match a user. In those
> cases I would like to have a boolean false returned, but instead I get an empty
> array - which of course is entirely according to the functions "RETURN SETOF
> users" statement.
>
> Is this little problem solvable, or will I have to learn to live with the empty
> array?

You can't return different return-types. Either return forever a record
or an bool.

But you can use select exists( select * from log_in( ...) ) to get
true/false it there a user or not.


Andreas
--
Andreas Kretschmer
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On 2009-11-18, Thomas Løcke <thomas.granvej6@gmail.com> wrote:
> --001517402ba882fac30478a73b83
> Content-Type: text/plain; charset=ISO-8859-1
>
> Hey all,
>
> http://pastebin.com/f1015226d
>
> The above function appears to be doing exactly what I want: Fetch the users
> data and update the visits column, if the supplied credentials match a user.
>
> My problem is what happens when the credentials don't match a user. In those
> cases I would like to have a boolean false returned, but instead I get an
> empty array - which of course is entirely according to the functions "RETURN
> SETOF users" statement.
>
> Is this little problem solvable, or will I have to learn to live with the
> empty array?

array? how are you calling it?

your function seems basically equivalent to

 UPDATE users SET lastvisit = now(), visits = visits + 1
     WHERE username = uname AND password = passwd
     RETURNING id;


anyway you'll have to look at the number of results returned, or
re-write it to only return a single result (I'm assumuing you don't
allow multiple accounts with the same username and password)
then you can return a special value for not found (perhaps 0)


personally I'd go with the sql given above and use apropriate means to
ask how many results were returned.

 pg_num_rows(), FOUND,  etc...

OTOH you say array, perhaps your chosen platform already treats an
array with zero elemants like false?

On 2009-11-20, Jasen Betts <jasen@xnet.co.nz> wrote:
> On 2009-11-18, Thomas Løcke <thomas.granvej6@gmail.com> wrote:
>> --001517402ba882fac30478a73b83
>> Content-Type: text/plain; charset=ISO-8859-1
>>
>> Hey all,
>>
>> http://pastebin.com/f1015226d

> your function seems basically equivalent to
>
>  UPDATE users SET lastvisit = now(), visits = visits + 1
>      WHERE username = uname AND password = passwd
>      RETURNING id;
      --------------

should be:
  RETURNING *;

oops.