Hi Junjie, Thanks for the update and also for your endruance in going through this tedious process in order to add bloom filtering to Parquet.
I understand that your proposal is to go forward with xxHash instead of the eralier murmur3, which you suggest to deprecate. Since the murmur3 hash was never released, I think it could be completely removed from the spec instead of just getting deprecated. What is your opinion on this? Thanks, Zoltan On Wed, Jul 3, 2019 at 3:31 PM 俊杰陈 <[email protected]> wrote: > I see, thanks for guiding on this. > > Per discussion in this thread and some investigation about changes on > current java and c++ implementation, and I think that is not hard to > handle. So I propose to use xxHash (the XXH64 version) as the default > hash strategy and deprecate previous murmur3 hash. > > I will update vote thread as well to make it clearer to all. > > > On Wed, Jul 3, 2019 at 6:08 PM Zoltan Ivanfi <[email protected]> > wrote: > > > > Hi Junjie, > > > > I think the vote is ambigous in its current form (can people vote on one > > option only or can they vote on both?) and has a low chance of getting > > votes in general because it's not a yes/no question but a > > choose-an-approach question instead. I think most contributors would > accept > > the hash chosen based on a community discussion but would be reluctant to > > make that choice themselves in the form a vote because it requires a much > > deeper dive into the technical intricacies involved. The committers are > > experienced in the parquet code base but may not be as experienced in > bloom > > filters as you are. > > > > In my opinion, to get bloom filtering into parquet-mr, you should > convince > > the committers that the proposal is viable by addressing their concerns > > (which I believe you have done), and not by delegating the task of making > > choices to them. I would suggest that you propose which one (or both) of > > the hashes should be included, summarize your motivations in this thread > > and if you don't get any objections for a day or two, call a YES/NO vote > > for that specific proposal in a separate thread. > > > > Thanks, > > > > Zoltan > > > > On Tue, Jul 2, 2019 at 3:52 AM 俊杰陈 <[email protected]> wrote: > > > > > Any thoughts from other committers and developers? > > > > > > I 'd like to start a vote firstly, you could either provide your input > here > > > or on vote thread. > > > > > > > > > > > > On Mon, Jul 1, 2019 at 8:20 PM Zoltan Ivanfi <[email protected]> > > > wrote: > > > > > > > Hi, > > > > > > > > I would like to clarify one point of my previous e-mail: While I > reasoned > > > > that for compressions and encodings we should avoid picking > algorithms > > > > superseded by better ones, I also reasoned that for bloom filters we > do > > > not > > > > necessarily have to be as strict, because a reader with missing > > > > implementation will still be able to read data from files that > contain > > > > unsupported bloom filter data structures. > > > > > > > > Personally I'm fine with moving forward with the current hash > proposal, > > > > even if the chosen algorithm is not considered to be the best of its > > > class. > > > > > > > > Br, > > > > > > > > Zoltan > > > > > > > > On Sun, Jun 30, 2019 at 11:02 PM Jim Apple <[email protected]> > wrote: > > > > > > > > > On 2019/06/28 16:43:23, Ryan Blue <[email protected]> > wrote: > > > > > > I agree with Zoltan. Since we want to ensure compatibility, it > would > > > be > > > > > > better to choose the best option now instead of making everyone > > > support > > > > > two > > > > > > options forever. > > > > > > > > > > I'd guess there probably isn't a single best option. I suspect > there's > > > a > > > > > tradeoff between ease of implementation and speed, for instance, > since > > > I > > > > > expect it's easy to find an MD5 library in most programming > languages > > > and > > > > > operating systems, yet MD5 is very slow compared to > non-cryptographic > > > > hash > > > > > functions designed for speed like xxhash. > > > > > > > > > > There's also a significant amount of variability across processor > > > > families > > > > > (64-bit multiply-shift in ARM vs x86-64) or even different > versions of > > > > the > > > > > same processor family (CLHash in Haswell vs. Sandy Lake). There are > > > also > > > > > quality tradeoffs that depend on the average bye length of the > input > > > (FNV > > > > > vs vhash) or how much L1 cache the user wants to use for the hash > > > > function > > > > > (tabulation hashing vs. multiply-shift). > > > > > > > > > > To deal with this level of ambiguity, I'd suggest that v1 should > > > include > > > > a > > > > > hash function that works well for certain common environments. As > far > > > as > > > > I > > > > > know, murmur and xxhash would both fit that bill. > > > > > > > > > > > > > > > > > > -- > > > Thanks & Best Regards > > > > > > > -- > Thanks & Best Regards >
