To extend the existing index

[kerkathy]

Hi,
Tks for this awesome repo beforehand!
I'm performing some data augmentation to the Wiki corpus, and hope to build a dense index using faiss for it.
Is the best solution to simply re-index the whole corpus (original+augmented), or is there a way to just index the augmented corpus, then combine it with the index you provided already?
Reading docs/usage-index.md, there seems to be a functionality of combining indices built from different shards, so I suppose there's a way (or even a hack :P) of combining two indices? but I'm not sure how to do so...

Any suggestion will be appreciated!

[kerkathy]

As a follow-up, I figured out that for Faiss we can use sth like

python -m pyserini.index.merge_faiss_indexes \
    --prefix faiss_index/ \
    --shard-num 2

but what about lucene index? is there anything similar?