Re: Crash in gist insertion on pathological box data

>>>>> "Teodor" == Teodor Sigaev <teodor(at)sigaev(dot)ru> writes:

>> even further. And what confidence do you have that this change
>> eliminates all forms of the problem, anyway?

Teodor> Yes, I think. Because that part of code ( if (IS_BADRATIO)
Teodor> {...} ) is a corner case itself. In example from Andrew, all
Teodor> boxes are placed to one page because of floating-point
Teodor> rounding.

Yes, it's a corner case, but it arose in real-world data (the test
data set is contrived, but that's simply because it was the easiest
way to demonstrate the bug without access to the real data, which
had a much larger variation in box sizes).

Teodor> We could check IS_BADRATIO again and if it's just put one
Teodor> half of all boxes on one page and another half to the another
Teodor> page as it does if all boxes are equal. But FPeq() seemed to
Teodor> me a simpler solution and FP* comparisons are widely used in
Teodor> geometry.

I think that not only does there need to be another IS_BADRATIO check,
but also there needs to be some sort of backstop in gistSplit or
gistUserPicksplit to either recover or (as a last resort) error out
cleanly rather than crash the entire db in cases that would result in
infinite recursion.

--
Andrew (irc:RhodiumToad)