Re: WIP fix proposal for bug #6123

Tom Lane <tgl@sss.pgh.pa.us> wrote:
> "Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
>> At any rate, I think we might want to apply Tom's patch for this
>> while 9.3 is still early in development, to see what else might
>> shake out from it while there is still plenty of time to fix any
>> issues.  It's now looking good from my perspective.
> 
> I just re-read the thread to refresh my memory.  It seems that we
> pretty much had consensus on throwing an error if any operation
> fired by a BEFORE UPDATE/DELETE trigger changes the target row,
> unless the trigger returns NULL to skip the update/delete.  It is
> not clear to me however whether we had consensus about what to do
> with SELECT FOR UPDATE locking cases.  The last patch posted in
> the thread was here:
> 
> http://archives.postgresql.org/pgsql-hackers/2012-01/msg01241.php
> 
> That message includes an example of the FOR UPDATE problem case
> and says that fixing it would require significantly more work.  Do
> we want to worry about tackling that now, or shall we be satisfied
> with fixing the trigger cases?
As you said in the referenced message, the FOR UPDATE issue seems
orthogonal and should probably be addressed separately.
> Also, it doesn't appear that we ever got around to preparing
> documentation updates, but I think we definitely need some if
> we're going to start throwing errors for things that used to be
> allowed.  Since Kevin has the most field experience with this
> problem, I'd like to nominate him to write some docs ...
OK, will do.  The "redo the DELETE and RETURN NULL" workaround is
not at all obvious; we should definitely include an example of that.
-Kevin