Forum OpenACS Q&A: todo_daily_sweep errors (trying to convert null timestamp to date)

I get the following:

ERROR:  Unable to convert null timestamp to date

whenever todo_daily_sweep occurs.  The SQL that it's using is:

select user_id from todo_user_preferences where
notification_interval>0 and
(sysdate()>=last_notification+notification_interval-0.01) or
last_notification is NULL

I assume this is a holdover from Oracle, which deals with NULL
wrong, but correct me if that's not the case.  How do I fix this
query, so I can use the todo notification system?

No it's a bug introduced in one of the PG 7.0 subversions, which
handles NULL wrong (NULLification should hold true for *all* types,
there should never be a "can't convert NULL" error).

This PG bug's fixed in PG 7.1 pre-beta, I tested it yesterday.  By
coincidence I was working on this very same problem as someone else
e-mailed me a bug report about it a few days ago.

I'll be updating the CVS tree with about a 1/2 dozen or so bug fixes
for various things that you and others have posted about recently.
I'll not get everything fixed, but some things, at least...

I'll post an announcement and list of bug fixes when I get done.