> On Mon, Mar 14, 2022 at 11:02:16AM -0400, Robert Haas wrote:
> On Mon, Mar 14, 2022 at 10:57 AM Dmitry Dolgov <9erthalion6@gmail.com> wrote:
> > Well, yeah, the commit message is somewhat clumsy in this regard. It
> > works almost in the way you've described, except if the list is all
> > constants and long enough to satisfy the threshold then *first N
> > elements (where N == threshold) will be jumbled -- to leave at least
> > some traces of it in pgss.
>
> But that seems to me to be a thing we would not want. Why do you think
> otherwise?
Hm. Well, if the whole list would be not jumbled, the transformation
would look like this, right?
WHERE x in (1, 2, 3, 4, 5) -> WHERE x in (...)
Leaving some number of original elements in place gives some clue for
the reader about at least what type of data the array has contained.
Which hopefully makes it a bit easier to identify even in the collapsed
form:
WHERE x in (1, 2, 3, 4, 5) -> WHERE x in (1, 2, ...)
> > I'm not sure if I follow the last point. WHERE x in (1,3) and x =
> > any(array[1,3]) are two different things for sure, but in which way are
> > they going to be mixed together because of this change? My goal was to
> > make only the following transformation, without leaving any uncertainty:
> >
> > WHERE x in (1, 2, 3, 4, 5) -> WHERE x in (1, 2, ...)
> > WHERE x = any(array[1, 2, 3, 4, 5]) -> WHERE x = any(array[1, 2, ...])
>
> I understand. I think it might be OK to transform both of those
> things, but I don't think it's very clear either from the comments or
> the nonexistent documentation that both of those cases are affected --
> and I think that needs to be clear. Not sure exactly how to do that,
> just saying that we can't add behavior unless it will be clear to
> users what the behavior is.
Yep, got it.