Fast incremental update with occasional reindexing

[npip99]

I'm not sure if I'm missing something in the documentation, but how do we periodically reindex new embeddings? Having a diskann index makes "INSERT" incredibly slow.

This is the behavior that I observe:

Initial Index

CREATE INDEX ix_chunk_embedding
    ON chunk
    USING diskann (embedding)
    WHERE (indexed = true)

(The indexed = true condition is for easily bringing rows into and out of the index.)

Fresh Index

SELECT pg_size_pretty(pg_relation_size('ix_chunk_embedding')) AS index_size;
 index_size 
------------
 24 kB
(1 row)

Add rows to index

UPDATE chunk
SET indexed = true
WHERE id IN [... 500 ids ...];

This takes 4.1 seconds. The only reason why i'm doing indexed = true, is so that appending rows to the database doesn't take forever.

Check Index size again

SELECT pg_size_pretty(pg_relation_size('ix_chunk_embedding')) AS index_size;
 index_size 
------------
 4024 kB
(1 row)

Reindex

REINDEX INDEX ix_chunk_embedding;

This runs almost instantly (<100ms?)

SELECT pg_size_pretty(pg_relation_size('ix_chunk_embedding')) AS index_size;
 index_size 
------------
 352 kB
(1 row)

And it's over 10x smaller.

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My issue is that incremental updates are both incredibly slow, and also not space efficient. Is there a way to disable incremental indexing altogether? I don't mind if incrementally indexed rows don't show up in recall, because I can just do SET indexed = true and then follow-up with a REINDEX CONCURRENTLY. Right now, I have no efficient way to do this.

Theoretically, there should be ways to make updates should be more efficient (MSFT advertises 1000 QPS and sub-ms latency for inserts https://youtu.be/BnYNdSIKibQ?t=352), but even then a SET LOCAL diskann_suppress_indexing = on; to disable INSERT/UPDATE indexing would still be useful. Drop+Recreate doesn't work because then queries stop working.