Re: Is a heads-up in 9.1 in order regarding the XML-related changes in 9.2?

Hi

As it stands, we're going to release 9.1, knowing that 9.2 will change the
behavior of XPATH. This brings forth the question whether we should somehow
warn about that in either the release notes or the documentation of 9.1

If we don't, then applications developed on 9.1 might contain workarounds for
the deficiencies of XPATH in that version (like for example manually escaping
its output), which make them break on 9.2. That seems a bit unfriendly.

OTOH, had we committed the changes to 9.2 a month or two from now, than
9.1 certainly couldn't have warned about them. So maybe it shouldn't thus
warn now, either.

Is there an establishes practice for situations like this, i.e. a behavior-
changing bug-fix committed to X.Y+1 before X.Y is released?

best regards,
Florian Pflug

Florian Pflug <fgp(at)phlo(dot)org> writes:
> Is there an establishes practice for situations like this, i.e. a behavior-
> changing bug-fix committed to X.Y+1 before X.Y is released?

Generally, we do nothing. It's a bit premature (in fact a lot
premature) to assume that the current behavior of HEAD is exactly what
will be released in 9.2, but putting statements about it into 9.1 docs
would amount to assuming that. It's the job of the 9.2 release notes
to point out incompatibilities, not the job of the 9.1 docs to guess
what will happen in the future.

If you think that the incompatibilities in question are so earth-shaking
as to require retroactive advance warnings, maybe we should reconsider
whether they're a good thing to do at all.

regards, tom lane

On Jul28, 2011, at 01:28 , Tom Lane wrote:
> Florian Pflug <fgp(at)phlo(dot)org> writes:
>> Is there an establishes practice for situations like this, i.e. a behavior-
>> changing bug-fix committed to X.Y+1 before X.Y is released?
>
> Generally, we do nothing. It's a bit premature (in fact a lot
> premature) to assume that the current behavior of HEAD is exactly what
> will be released in 9.2, but putting statements about it into 9.1 docs
> would amount to assuming that. It's the job of the 9.2 release notes
> to point out incompatibilities, not the job of the 9.1 docs to guess
> what will happen in the future.

Fair enough.

> If you think that the incompatibilities in question are so earth-shaking
> as to require retroactive advance warnings, maybe we should reconsider
> whether they're a good thing to do at all.

Certainly not earth-shaking, no. Also an obvious improvement, and probably
equally likely to fix existing applications as they are to break them. So
let's by all means not revert them.

I simply though that putting a warning about XPATH() escaping deficiencies
might save some people the trouble of (a) finding out about that the hard
way and (b) developing work-arounds which are bound to be broken by 9.2.

I'm not saying we must absolutely do so - heck, I'm not even totally
convinced myself that we even should do so. I simply happened to realize
today that the timing was a bit unfortunate, figured it wouldn't hurt to
get additional opinions on this, and thus asked.

best regards,
Florian Pflug