On Wed, Jun 18, 2008 at 3:25 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > There isn't any really nice way to do that :-(. You could put a wrapper > function around int4in but it would not help, because the internal API > for datatype input functions doesn't support having them return NULL > (see InputFunctionCall in the sources). I've read src/backend/utils/fmgr/README and it states that returning NULL is just a matter of setting isnull to true in the FunctionCallInfo struct, and provides a convenience macro, PG_RETURN_NULL. But then, in InputFunctionCall, I presume you're referring to the logic that that only allows NULL to be returned if the source input string is also NULL, otherwise raising an error. At a basic level, you're suggesting I need to take out this NULL check in InputFunctionCall to get the capability I'm looking for? Any idea why the input functions were designed this way? For users migrating from other RDBMs, if no one else, being able to return NULL from an input function seems to be a valuable feature. I might use this hacked functionality to return NULL for '0000-00-00' dates which MySQL foolishly accepts. Maybe it's only useful to former MySQL users thanks, Dave
