Peter Geoghegan <p...@heroku.com> writes:
> On Thu, Jul 17, 2014 at 7:47 AM, Alvaro Herrera
> <alvhe...@2ndquadrant.com> wrote:
>> I don't understand the point of having these GIN_EXCLUSIVE / GIN_SHARED
>> symbols. It's not like we could do anything different than
>> BUFFER_LOCK_EXCLUSIVE etc instead. It there was a GinLockBuffer() it
>> might make more sense to have specialized symbols, but as it is it seems
>> pointless.
> It's a pattern common to the index AMs. I think it's kind of pointless
> myself, but as long as we're doing it we might as well be consistent.
I think that to the extent that these symbols are used in APIs above the
direct buffer-access layer, they are useful --- for example using
BT_READ/BT_WRITE in _bt_search calls seems like a useful increment of
readability. GIN seems to have less of that than some of the other AMs,
but I do see GIN_SHARE being used that way in some calls.
BTW, there's one direct usage of BUFFER_LOCK_EXCLUSIVE in the GIST code
as well, which should probably be replaced with GIST_EXCLUSIVE if we're
trying to be consistent.
regards, tom lane
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