Re: SP-GiST bug.

> The point I'm making is that the scenario your test case exposes is not
> an infinite loop of picksplits, but an infinite loop of choose calls.

Thank you, now I see what I missed before. After some brainstorming, it's
possible to use '\0' only as end of string marker. The idea is: when we split
allthesame tuple to upper/lower we copy node label to upper tuple instead of set
it to '\0'. Node labels of lower tuple will be unchanged but should be ignored
for reconstructionValue - and they are ignored because of allTheSame flag. See
attached patch.

Unfortunately, it will break on-disk compatibility. Although it will not cause a
panic/error/coredump allTheSame approach will not find tuples. Users should
recreate spgist indexes over text column.

> It's certainly possible that we could/should change what checkAllTheSame
> is doing --- on re-reading the comment, I'm not really sure that the
> scenario it's concerned about can happen. However, that will not fix

I rewrited a patch to fix missed way - allTheSame result of picksplit and tooBig
is set. I believe this patch is still needed because it could make a tree more
efficient as it was demonstrated for quad tree.

this patch doesn't break on-disk compatibility, although index recreation is
recommended.

--
Teodor Sigaev E-mail: teodor(at)sigaev(dot)ru
WWW: http://www.sigaev.ru/