SQLite create_storage_provider() is slow when database has data already

[gvanrossum]

What is it doing? I have a db with ~2500 messages and create_storage_provider() took 230 seconds! Something must be quadratic or doing too many small db queries or going out to an embedding server?

[gvanrossum]

The time spent is almost all in SqliteRelatedTermsFuzzy.

[gvanrossum]

Adding (key, embedding) pairs to the vector base one at a time is quadratic. Updated the signature of VectorBase.add_embeddings() to allow passing in keys, and used that to pass all keys at once. This makes the time spent in SqliteRelatedTermsFuzzy go away -- now we only have to worry about SqliteMessageTextIndex which needs a similar update.