From: | "Hitoshi Harada" <umi(dot)tanuki(at)gmail(dot)com> |
---|---|
To: | "David Rowley" <dgrowley(at)gmail(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Windowing Function Patch Review -> NTILE function |
Date: | 2008-11-10 14:19:02 |
Message-ID: | e08cc0400811100619w46a1b013x2051f6a8f2dad116@mail.gmail.com |
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Lists: | pgsql-hackers |
2008/11/9 David Rowley <dgrowley(at)gmail(dot)com>:
>
> I've done a little testing with NTILE(). I think a check should be added to
> the ntile() function in wfunc.c.
>
> david=# select name,salary,ntile(0) over (order by salary) as n from
> employees;
> ERROR: floating-point exception
> DETAIL: An invalid floating-point operation was signaled. This probably
> means an out-of-range result or an invalid operation, such as division by
> zero.
>
> I tracked that message back to the signal handler in postgres.c :-( simple
> fix though. Any value less than 1 does not really make sense to me.
>
> Maybe we should add something like:
>
> if (PG_WINDOW_ARG(0) < 1)
> elog(ERROR, "negative or zero ntile argument not allowed");
>
> What do you think?
>
> Oracle errors out on less than 1, Sybase seems not to have ntile.
> MSSQL 2008 also errors out on less than 1
>
> David.
>
>
I am so sorry but I missed this thread.
I found in the spec:
1) If NT is the null value, then the result is the null value.
2) If NT is less than or equal to 0 (zero), then an exception
condition is raised: data exception
― invalid argument for NTILE function.
My patch violates both of two :-( As you point, we must add the value
check and also allow null case to return null.
will be fixed soon.
Regards,
--
Hitoshi Harada
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