First of all, thank you again for this spec. I would recommend anyone else curious about ALP (or wanting to read a well written technical spec) to read Prateek's document -- it is really nice.
I would like to raise two more items (I am not sure the spec needs to be changed to accommodate them, but I do think we should discuss them): 1) Interleaving the bitpacked values (this was suggested by Peter Boncz). Specifically, I recommend we consider the technique described in the FASTLANES paper[1] (figure 1) that interleaves bit-packed values in a pattern that enables decoding multiple values using a single SIMD instruction and is GPU friendly. To be clear we don't need to implement all of the techniques described in that paper, but I think the interleaving is worth considering. It seems like the current prototype uses linear bitpacking[2] 2) The layout for exceptions, specifically making sure that the spec allows other potential layouts in the future to make them more GPU friendly. One proposal is in the G-ALP[3] paper, but it comes with tradeoffs (e.g. it requires additional storage overhead). Andrew [1]: https://www.vldb.org/pvldb/vol16/p2132-afroozeh.pdf [2]: https://github.com/apache/arrow/pull/48345/changes#diff-f9ab708cab94060b4067fff0a6739e9c3751b450422115663b2bd0badfcc748bR801 [3]: https://dl.acm.org/doi/10.1145/3736227.3736242 On Wed, Jan 14, 2026 at 3:21 PM Andrew Lamb <[email protected]> wrote: > Here is a PR that turns Prateek's document into markdown in the > parquet-format repo > - https://github.com/apache/parquet-format/pull/548 > > I am a little worried we will have two set of parallel comments (one in > the google doc and one in the PR) > > However, the spec is of sufficient quality (thanks, again Prateek) that it > would be possible for another language implementation to be attempted. > > Andrew > > > > On Wed, Jan 14, 2026 at 8:54 AM Andrew Lamb <[email protected]> > wrote: > >> I plan to help turn the document into a PR to parquet-format later today >> >> And again thank you Prateek and everyone for helping make this happen >> >> Andrew >> >> On Wed, Jan 14, 2026 at 6:34 AM Antoine Pitrou <[email protected]> >> wrote: >> >>> >>> Yes, I'd really rather comment on the final spec, rather than a Google >>> doc. >>> >>> (also, Google Doc comments are not terrific for non-trivial discussions) >>> >>> >>> Le 14/01/2026 à 10:37, Gang Wu a écrit : >>> > Is it better to create a PR against >>> https://github.com/apache/parquet-format >>> > so >>> > it can become the single source of truth of the Parquet-ALP spec? >>> > >>> > On Wed, Jan 14, 2026 at 9:34 AM Julien Le Dem <[email protected]> >>> wrote: >>> > >>> >> Thank you Micah for the detailed review! >>> >> Who else needs to do a round of reviews on the spec before we can >>> finalize >>> >> it? >>> >>> >>>
