[FEATURE] support vector and FTS indexes in lancedb connector

[badmonster0]

What is the use case?
support vector and FTS indexes in lancedb connector

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[georgeh0]

Created #1358. During test, noticed LanceDB's LTS support is for Cloud and Enterprise edition only. Nevertheless, we can checkin this feature first and waiting for users response to see if there's any problems.

[badmonster0]

thanks @georgeh0 !! cc @prrao87

[prrao87]

Thank you! Will try it out in some workflows and raise issues if they arise.

[prrao87]

Hi @georgeh0, I think the current implementation of FTS indexes (specifically, this statement) is incorrect. LanceDB OSS does support FTS - but this is totally our fault (it's poorly documented, and I'm fixing that part here.

Basically, when working with a LanceDB AsyncTable and using an async API, which is what CocoIndex defaults to, we need to avoid using create_fts_index and instead use the more general method create_index, as defined in this async test in our test suite. The documentation issue arose on our end because an older API relied on tantivy (a full-text search engine in the Rust ecosystem), before we had an async Python API, but we then migrated to a native Lance format-supported FTS index to support async tables more fully.

This minimal example should show how to interface with the FTS index in LanceDB open source (no need for enterprise edition).

import asyncio
import lancedb
import polars as pl
from lancedb.index import FTS

data = pl.DataFrame(
    {
        "id": [1, 2],
        "text": ["His first language is spanish", "Her first language is english"],
    }
)

async def main(data: pl.DataFrame):
    uri = "ex_lancedb"
    db = await lancedb.connect_async(uri)
    tbl = await db.create_table("my_text", data=data, mode="overwrite")

    await tbl.create_index("text", config=FTS(language="English"))

    response = await tbl.search("spanish", query_type="fts")

    result = await response.limit(1).to_polars()
    print(result)


if __name__ == "__main__":
    asyncio.run(main(data))

Should output:

shape: (1, 3)
┌─────┬───────────────────────────────┬──────────┐
│ id  ┆ text                          ┆ _score   │
│ --- ┆ ---                           ┆ ---      │
│ i64 ┆ str                           ┆ f32      │
╞═════╪═══════════════════════════════╪══════════╡
│ 1   ┆ His first language is spanish ┆ 0.693147 │
└─────┴───────────────────────────────┴──────────┘

Hope this can be addressed inside cocoindex! For immediate reference, the test suite in test_index.py should contain all the async tests for index creation, and it's designed so the relevant index and their parameters can be passed in a more general way. For now, I think just a regular FTS index that accepts its relevant parameters, and an IVF_PQ index that also accepts its relevant parameters should be sufficient.

Thanks!

[badmonster0]

Thanks for keeping us informed @prrao87 , we will take a look! cc @georgeh0