incremental index construction

[joshua-gould]

I would like the option to build an index incrementally. Thanks.

[lmcinnes]

This would certainly be a good thing. I believe that this is potentially possible, but it will definitely be slower than a bulk/batch build. I'm not sure when I or other contributors will have time to implement such a thing unfortunately -- thanks for reporting the issue though, this would definitely be a useful feature to have,