Re: [COMMITTERS] pgsql: Code cleanup in the wake of recent LWLock refactoring.

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Wed, Feb 10, 2016 at 11:08 AM, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
>> (Sorry if this was discussed already, I haven't been paying attention)
>>
>> LWLockAssign() is used by extensions. Are we OK with just breaking them,
>> requiring them to change LWLockAssign() with the new mechanism, with #ifdefs
>> to support multiple server versions? Seems like it shouldn't be too hard to
>> keep LWLockAssign() around for the benefit of extensions, so it seems a bit
>> inconsiderate to remove it.

> If there's a strong feeling that we should keep the old APIs around,
> we can do that, but I think that (1) if we don't remove them now, we
> probably never will and (2) they are vile APIs. Allocating the number
> of add-in lwlocks that are requested or a minimum of 3 is just awful.
> If somebody allocates a different number than they request it
> sometimes works, except when combined with some other extension, when
> it maybe doesn't work. This way, you ask for an LWLock under a given
> name and then get it under that name, so if an extension does it
> wrong, it is that extension that breaks rather than some other one. I
> think that's enough benefit to justify requiring a small code change
> on the part of extension authors that use LWLocks, but that's
> obviously biased by my experience maintaining EDB's extensions, and
> other people may well feel differently.

FWIW, I wasn't paying attention either, but I'm convinced by Robert's
argument. Avoiding coupling between extensions is worth an API break.

regards, tom lane