Re: Sparse bit set data structure

On Wed, Mar 13, 2019 at 3:18 PM Heikki Linnakangas <hlinnaka@iki.fi> wrote:
> I started to consider rewriting the data structure into something more
> like B-tree. Then I remembered that I wrote a data structure pretty much
> like that last year already! We discussed that on the "Vacuum: allow
> usage of more than 1GB of work mem" thread [2], to replace the current
> huge array that holds the dead TIDs during vacuum.
>
> So I dusted off that patch, and made it more general, so that it can be
> used to store arbitrary 64-bit integers, rather than ItemPointers or
> BlockNumbers. I then added a rudimentary form of compression to the leaf
> pages, so that clusters of nearby values can be stored as an array of
> 32-bit integers, or as a bitmap. That would perhaps be overkill, if it
> was just to conserve some memory in GiST vacuum, but I think this will
> turn out to be a useful general-purpose facility.

Yeah, that sounds pretty cool.

-- 
Robert Haas
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