Re: [PATCH 1/3] diff histogram: intern strings

From: Phillip Wood <phillip.wood123@gmail.com>
Date: Nov 19, 2021, 10:05 UTC
Message-ID: <86d38148-7b97-76aa-148b-346cc179615a@gmail.com>
In-Reply-To: <YZZ0e7CCGW5QbQlW@coredump.intra.peff.net>

On 18/11/2021 15:42, Jeff King wrote:

Show 12 quoted lines

> 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.

Best Wishes

Phillip