Re: [HACKERS] WAL logging problem in 9.4.3?

On Thu, Jul 12, 2018 at 05:12:21PM +0300, Heikki Linnakangas wrote:
> Doesn't have to be a trigger, could be a CHECK constraint, datatype input
> function, etc. Admittedly, having a datatype input function that inserts to
> the table is worth a "huh?", but I'm feeling very confident that we can
> catch all such cases, and some of them might even be sensible.

Sure, but do we want to be that invasive? Triggers are easy enough to
block because those are available directly within cstate so you would
know if those are triggered. CHECK constraint can be also easily looked
after by looking at the Relation information, and actually as DEFAULT
values could have an expression we'd want to block them, no? The input
datatype is well, more tricky to deal with as there is no actual way to
know if the INSERT is happening within the context of a COPY and this
could be just C code. One way to tackle that would be to enforce the
optimization to not be used if a non-system data type is used when doing
COPY...

Disabling entirely the optimization for any relation which has a CHECK
constraint or DEFAULT expression basically applies to a hell lot of
them, which makes the optimization, at least it seems to me, useless
because it is never going to apply to most real-world cases.
--
Michael