On Mon, Aug 15, 2022 at 12:39 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> On Fri, Jul 22, 2022 at 10:43 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> >
> > On Tue, Jul 19, 2022 at 1:30 PM John Naylor
> > <john.naylor@enterprisedb.com> wrote:
> > >
> > >
> > >
> > > On Tue, Jul 19, 2022 at 9:11 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > >
> > > > I’d like to keep the first version simple. We can improve it and add
> > > > more optimizations later. Using radix tree for vacuum TID storage
> > > > would still be a big win comparing to using a flat array, even without
> > > > all these optimizations. In terms of single-value leaves method, I'm
> > > > also concerned about an extra pointer traversal and extra memory
> > > > allocation. It's most flexible but multi-value leaves method is also
> > > > flexible enough for many use cases. Using the single-value method
> > > > seems to be too much as the first step for me.
> > > >
> > > > Overall, using 64-bit keys and 64-bit values would be a reasonable
> > > > choice for me as the first step . It can cover wider use cases
> > > > including vacuum TID use cases. And possibly it can cover use cases by
> > > > combining a hash table or using tree of tree, for example.
> > >
> > > These two aspects would also bring it closer to Andres' prototype, which 1) makes review easier and 2) easier to
preserveoptimization work already done, so +1 from me.
> >
> > Thanks.
> >
> > I've updated the patch. It now implements 64-bit keys, 64-bit values,
> > and the multi-value leaves method. I've tried to remove duplicated
> > codes but we might find a better way to do that.
> >
>
> With the recent changes related to simd, I'm going to split the patch
> into at least two parts: introduce other simd optimized functions used
> by the radix tree and the radix tree implementation. Particularly we
> need two functions for radix tree: a function like pg_lfind32 but for
> 8 bits integers and return the index, and a function that returns the
> index of the first element that is >= key.
I recommend looking at
https://www.postgresql.org/message-id/CAFBsxsESLUyJ5spfOSyPrOvKUEYYNqsBosue9SV1j8ecgNXSKA%40mail.gmail.com
since I did the work just now for searching bytes and returning a
bool, buth = and <=. Should be pretty close. Also, i believe if you
left this for last as a possible refactoring, it might save some work.
In any case, I'll take a look at the latest patch next month.
--
John Naylor
EDB: http://www.enterprisedb.com
