You might not need a CRDT

Re:You might not need a CRDT by lewisjoe on Monday December 05, 2022 @08:45PM (#33874788)

Yes, offline edits tend to generate larger units of delta. The larger the deltas, the more difficult or even impossible it is to merge with a sensible outcome for all parties. Falling back to manual merging will be an useful feature.

But wouldn't this mean the CRDT will be an evergrowing set like git? Is this even practical like when say, working with a thousand page book? To me it looks like it breaks the possibility of garbage collecting portions of CRDT which will make it harder to adopt in real-world apps.

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Re:You might not need a CRDT by josephg on Monday December 05, 2022 @08:56PM (#33874874)

> Is this even practical like when say, working with a thousand page book?

Remarkably, yeah its fine in practice. I've done a lot of work on this recently, doing crazy optimized bit packing for text CRDT data. The numbers are wild - all the metadata (insert positions, versions, etc) ends up only accounting for a few % of the final file size. Almost all of the final file size is the inserted characters themselves. And this is still true for files with complex editing histories (eg reconstructed from git repositories).

Diamond types does LZ4 compression of the inserted text data. In most of my examples, I save more bytes on disk by LZ4 compressing the text than I spend storing all the CRDT metadata. So the file on disk (with full history and change tracking) often ends up smaller than the final document.

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