litesearch

Fast hybrid search (text + vectors), automatically reranked.

NB If you’re reading this in GitHub readme, I recommend you read the more nicely formatted documentation format of this tutorial.

Litesearch is a lightweight library to set up a fastlite database with FTS5 and vector search capabilities using usearch.

Litesearch uses usearch sqlite extensions to provide fast vector search capabilities and combines it with sqlite’s FTS5 capabilities to provide hybrid search. - Litesearch uses fastlite, which is a lightweight wrapper around SQLite that makes SQLite database management delightful. It uses apsw rather than sqlite3 and provides best practices OOB. - Usearch is a cross-language package which provides vector search capabilities. We’re using its sqlite extensions here to provide fast vector search capabilities.

Lite search provides a simple way to setup this database using the database() method. You get a store with FTS5 and vector search capabilities using the get_store() method and you can search through the contents using the search() method.

Litesearch also provides document and code manipulation tools as part of the data module and onnx based text encoders as part of the utils module. - litesearch extends pymupdf Document and Page classes to extract texts, images and links easily. - litesearch provides onnx based text encoders which can be used to generate embeddings for documents and queries. - litesearch provides a quick code parsing utility to parse python files into code chunks for ingestion.

Get Started

fastlite and usearch will be installed automatically with litesearch if you do not have it already.

!pip install litesearch -qq

Litesearch only adds dependencies it needs, so you can use import * from litesearch without worrying about heavy dependencies. > First time import will try to setup usearch extensions and installing libsqlite3 if you do not have it already. mac also needs an extra step to add libsqlite3 into it’s LC_PATH. Check postfix.py for details.

from litesearch import *

database

db = database()
db.q('select sqlite_version() as sqlite_version')
[{'sqlite_version': '3.51.1'}]

Let’s try some of usearch’s distance functions

import numpy as np
embs = dict(
    v1=np.ones((100,),dtype=np.float32).tobytes(),      # vector of ones
    v2=np.zeros((100,),dtype=np.float32).tobytes(),     # vector of zeros
    v3=np.full((100,),0.25,dtype=np.float32).tobytes()  # vector of 0.25s
)
def dist_q(metric):
    return db.q(f'''
        select
            distance_{metric}_f32(:v1,:v2) as {metric}_v1_v2,
            distance_{metric}_f32(:v1,:v3) as {metric}_v1_v3,
            distance_{metric}_f32(:v2,:v3) as {metric}_v2_v3
    ''', embs)

for fn in ['sqeuclidean', 'divergence', 'inner', 'cosine']: print(dist_q(fn))
[{'sqeuclidean_v1_v2': 100.0, 'sqeuclidean_v1_v3': 56.25, 'sqeuclidean_v2_v3': 6.25}]
[{'divergence_v1_v2': 34.657352447509766, 'divergence_v1_v3': 12.046551704406738, 'divergence_v2_v3': 8.66433334350586}]
[{'inner_v1_v2': 1.0, 'inner_v1_v3': -24.0, 'inner_v2_v3': 1.0}]
[{'cosine_v1_v2': 1.0, 'cosine_v1_v3': 0.0, 'cosine_v2_v3': 1.0}]

store

A store is a table with FTS5 and vector search capabilities.

store = db.get_store()
store.schema
'CREATE TABLE [store] (\n   [content] TEXT NOT NULL,\n   [embedding] BLOB,\n   [metadata] TEXT,\n   [uploaded_at] FLOAT DEFAULT CURRENT_TIMESTAMP,\n   [id] INTEGER PRIMARY KEY\n)'

Let’s use a naive embedder for testing. > Checkout FastEncode in utils module for onnx based text encoders. > Check the examples folder for usage.

from sklearn.feature_extraction.text import TfidfVectorizer
txts, q = ['this is a text', "I'm hungry", "Let's play! shall we?"], 'playing hungry'
# this is naive vectoriser intended to showcase litesearch. In practice, use a proper text encoder.
def embed_texts(texts): return TfidfVectorizer(max_features=20000, stop_words='english').fit_transform(texts).toarray().astype(np.float16)
embs = embed_texts(txts + [q])  # last one is query
embs
array([[0.   , 0.   , 0.   , 0.   , 0.   , 1.   ],
       [1.   , 0.   , 0.   , 0.   , 0.   , 0.   ],
       [0.   , 0.577, 0.577, 0.   , 0.577, 0.   ],
       [0.619, 0.   , 0.   , 0.785, 0.   , 0.   ]], dtype=float16)

usearch also works with json embeddings, but using bytes leverages simd well.

rows = [dict(content=t, embedding=e.ravel().tobytes()) for t,e in zip(txts,embs[:-1])]
store.insert_all(rows)
<Table store (content, embedding, metadata, uploaded_at, id)>

Next steps

  • Check out the data module for document and code parsing utilities.
  • Check out the utils module for onnx based text encoders.
  • Check out the examples folder for complete examples.