On Fri, Nov 19, 2021 at 10:05:32AM +0000, Phillip Wood wrote: > On 18/11/2021 15:42, Jeff King wrote: > > On Thu, Nov 18, 2021 at 04:35:48PM +0100, Johannes Schindelin wrote: > > > > > I think the really important thing to point out is that > > > `xdl_classify_record()` ensures that the `ha` attribute is different for > > > different text. AFAIR it even "linearizes" the `ha` values, i.e. they > > > won't be all over the place but start at 0 (or 1). > > > > > > So no, I'm not worried about collisions. That would be a bug in > > > `xdl_classify_record()` and I think we would have caught this bug by now. > > > > Ah, thanks for that explanation. That addresses my collision concern from > > earlier in the thread completely. > > Yes, thanks for clarifying I should have been clearer in my reply to Stolee. > The reason I was waffling on about file sizes is that there can only be a > collision if there are more than 2^32 unique lines. I think the minimum file > size where that happens is just below 10GB when one side of the diff has > 2^31 lines and the other has 2^31 + 1 lines and all the lines are unique. Right, that makes more sense (and we are not likely to lift the 1GB limit anytime soon; there are tons of 32-bit variables and potential integer overflows all through the xdiff code). It's probably worth explaining this a bit in the commit message. I also, FWIW, found the subject confusing. I expected "intern" to refer to keeping a single copy of some strings. Maybe: Subject: diff histogram: skip xdl_recmatch for comparing records or something? -Peff
