Thread: Function with default value not replacing old definition of the function

Hi,<br /><br />Testcase: (8.4 CVS head)<br />====================<br /><br />CREATE OR REPLACE FUNCTION myfunc(y
int)<br/>RETURNS INTEGER AS $$<br />   select  100;<br />$$ language sql;<br /><br />CREATE OR REPLACE FUNCTION
myfunc(yint, x integer DEFAULT 100)<br /> RETURNS INTEGER AS $$<br />   select  200;<br />$$ language sql;<br /><br
/>selectmyfunc(10);<br /><br /> myfunc<br />----------<br />      100<br />(1 row) <br /><br />When create the same
functionagain by added one default value, while calling the function old function getting called. <br /><br />It seems
that,function with defval not making any sense, if we want to call the new function then we need to pass defval as
well.<br/><br />select myfunc(10,10);<br /><br /> myfunc<br /> ----------<br />       200<br /> (1 row) <br /><br />I
thinksecond function should replace the old definition of the function, inputs ?<br /><br /><br />Thanks,<br />Rushabh
Lathia<br/><a href="http://www.EnterpriseDB.com">www.EnterpriseDB.com</a><br /> 

Rushabh Lathia wrote:
> Hi,
> 
> Testcase: (8.4 CVS head)
> ====================
> 
> CREATE OR REPLACE FUNCTION myfunc(y int)
> RETURNS INTEGER AS $$
>    select  100;
> $$ language sql;
> 
> CREATE OR REPLACE FUNCTION myfunc(y int, x integer DEFAULT 100)
> RETURNS INTEGER AS $$
>    select  200;
> $$ language sql;
> 
> select myfunc(10);
> 
>  myfunc
> ----------
>       100
> (1 row)
> 
> When create the same function again by added one default value, while 
> calling the function old function getting called.
> 
> It seems that, function with defval not making any sense, if we want to 
> call the new function then we need to pass defval as well.

Hmm, good point, but I'm not sure that replacing the old function is 
always right.  For example, someone recently requested being able to say

select myfunc(10, DEFAULT);

so there would be some value to having both variants.

Do you have any comparisons with other systems (Oracle?) or other 
programming languages?

Hello

2008/12/11 Rushabh Lathia <rushabh.lathia@gmail.com>:
> Hi,
>
> Testcase: (8.4 CVS head)
> ====================
>
> CREATE OR REPLACE FUNCTION myfunc(y int)
> RETURNS INTEGER AS $$
>    select  100;
> $$ language sql;
>
> CREATE OR REPLACE FUNCTION myfunc(y int, x integer DEFAULT 100)
> RETURNS INTEGER AS $$
>    select  200;
> $$ language sql;
>
> select myfunc(10);
>
>  myfunc
> ----------
>       100
> (1 row)

no, it's little bit different

Default is only stored parameter value. You created two functions with
two different signatures

myfunc(int)
myfunc(int, int)

when you created function, we cannot check defaults, because we don't
know if anybody use default or not. And when you call function, then
postgres prefer function with most similar function.

regards
Pavel Stehule

>
> When create the same function again by added one default value, while
> calling the function old function getting called.
>
> It seems that, function with defval not making any sense, if we want to call
> the new function then we need to pass defval as well.
>
> select myfunc(10,10);
>
>  myfunc
> ----------
>       200
> (1 row)
>
> I think second function should replace the old definition of the function,
> inputs ?
>
>
> Thanks,
> Rushabh Lathia
> www.EnterpriseDB.com
>

2008/12/11 Rushabh Lathia <rushabh.lathia@gmail.com>:
>
>
> On Thu, Dec 11, 2008 at 12:40 PM, Pavel Stehule <pavel.stehule@gmail.com>
> wrote:
>>
>> Hello
>>
>>
>> when you created function, we cannot check defaults, because we don't
>> know if anybody use default or not. And when you call function, then
>> postgres prefer function with most similar function.
>
> Ok, but what if I want to call a second function with the default values.
> How can I call that function with default values?
>

it isn't possible yet (without DEFAULT keyword support).

you have to drop myfunc(int) first.

regards
Pavel Stehule

>>
>>
>> regards
>> Pavel Stehule
>>
>> >
>> > When create the same function again by added one default value, while
>> > calling the function old function getting called.
>> >
>> > It seems that, function with defval not making any sense, if we want to
>> > call
>> > the new function then we need to pass defval as well.
>> >
>> > select myfunc(10,10);
>> >
>> >  myfunc
>> > ----------
>> >       200
>> > (1 row)
>> >
>> > I think second function should replace the old definition of the
>> > function,
>> > inputs ?
>> >
>> >
>> > Thanks,
>> > Rushabh Lathia
>> > www.EnterpriseDB.com
>> >
>
>
>
> --
> Rushabh Lathia
> www.EnterpriseDB.com
>

"Pavel Stehule" <pavel.stehule@gmail.com> writes:
> no, it's little bit different

> Default is only stored parameter value. You created two functions with
> two different signatures

> myfunc(int)
> myfunc(int, int)

Yeah, we already bit this bullet with variadic functions --- if you havemyfunc(int, float)myfunc(int, variadic
float[])
then it's ambiguous which one should be used for call "myfunc(11, 12.5)".
The sanest answer I can see is "so, don't do that".
        regards, tom lane

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Hi,

Le 11 déc. 08 à 16:22, Tom Lane a écrit :
> Yeah, we already bit this bullet with variadic functions --- if you
> have
>     myfunc(int, float)
>     myfunc(int, variadic float[])
> then it's ambiguous which one should be used for call "myfunc(11,
> 12.5)".
> The sanest answer I can see is "so, don't do that".


Is there any warning level message at CREATE FUNCTION time for the
user/dba to know he's doing something... border line, almost shooting
himself in the foot?

I'd really welcome such an error message as a reminder to consider
seriously such a choice, which would not be though out in lot of cases
I suppose.

Regards,
- --
dim




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Dimitri Fontaine <dfontaine@hi-media.com> writes:
>> The sanest answer I can see is "so, don't do that".

> Is there any warning level message at CREATE FUNCTION time for the  
> user/dba to know he's doing something... border line, almost shooting  
> himself in the foot?

It's not that easy to produce a message that wouldn't be annoying noise.
In particular, it's hard to know whether functions in different schemas
would represent a problem or not.
        regards, tom lane

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Le 11 déc. 08 à 21:23, Tom Lane a écrit :
> It's not that easy to produce a message that wouldn't be annoying
> noise.

Something really amazing in PostgreSQL is the HINTs system in error
messages. Almost all the time thoses messages are focused and helping.
I'd see this warning as a HINT maybe: WARNING: variadic function xxx(int, int[]) already exists HINT: you would rather
notto mask it 

Well, I'm not sure WARNING HINTS are supported, it's more a way to
better explain the idea  than anything else.

The bottom line was that I'm betting DBA would be happy to know and
wouldn't consider it annoying noise, and for the kind of "Please, I
know what I'm doing" DBAs, maybe some kind of warning_level GUC would
be desirable?

> In particular, it's hard to know whether functions in different
> schemas
> would represent a problem or not.

I'd still vote in favor of the NOTICE/WARNING. I know I'd be happy to
have my beloved PostgreSQL being attentive and focused when maybe I'm
not. Even if this time I was.

Regards,
- --
dim




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