Обсуждение: error handling in cast functions for user defined types

Hi,

I'm writing a set of casts to/from various user defined
types.  As is unexpected, there are cases where one
data type doesn't neatly map to another (for certain
values).  In these cases I emit an INVALID_PARAMETER_VALUE
or OUT_OF_RANGE error -- depending on the situation.

But, should I also PG_RETURN_NULL()?  I note the
cast of int4's to int2's signal similar errors -- *but*
returns "(int2) value".

Is the return value just *ignored* when the error is
signaled?

Thanks!
--don

Don Y <pgsql@DakotaCom.Net> writes:
> I'm writing a set of casts to/from various user defined
> types.  As is unexpected, there are cases where one
> data type doesn't neatly map to another (for certain
> values).  In these cases I emit an INVALID_PARAMETER_VALUE
> or OUT_OF_RANGE error -- depending on the situation.

> But, should I also PG_RETURN_NULL()?

elog(ERROR) doesn't return to your function --- think of it as being
like exit().  So it's pointless to code anything after it.

            regards, tom lane

Tom Lane wrote:
> Don Y <pgsql@DakotaCom.Net> writes:
>> I'm writing a set of casts to/from various user defined
>> types.  As is unexpected, there are cases where one
>> data type doesn't neatly map to another (for certain
>> values).  In these cases I emit an INVALID_PARAMETER_VALUE
>> or OUT_OF_RANGE error -- depending on the situation.
>
>> But, should I also PG_RETURN_NULL()?
>
> elog(ERROR) doesn't return to your function --- think of it as being
> like exit().  So it's pointless to code anything after it.

Ah, OK.  "/* NOT REACHED */"

Thanks!
--don