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import lancedb
import os
import gradio as gr
from sentence_transformers import SentenceTransformer
from transformers import AutoTokenizer, AutoModelForSequenceClassification
import torch
import time
db = lancedb.connect(".lancedb")
TABLE = db.open_table(os.getenv("TABLE_NAME"))
VECTOR_COLUMN = os.getenv("VECTOR_COLUMN", "vector")
TEXT_COLUMN = os.getenv("TEXT_COLUMN", "text")
BATCH_SIZE = int(os.getenv("BATCH_SIZE", 32))
CROSS_ENCODER = os.getenv("CROSS_ENCODER")
retriever = SentenceTransformer(os.getenv("EMB_MODEL"))
cross_encoder = AutoModelForSequenceClassification.from_pretrained(CROSS_ENCODER)
cross_encoder.eval()
cross_encoder_tokenizer = AutoTokenizer.from_pretrained(CROSS_ENCODER)
def rerank(query, documents, k):
"""Use cross-encoder to rerank documents retrieved from the retriever."""
tokens = cross_encoder_tokenizer([query] * len(documents), documents, padding=True, truncation=True, return_tensors="pt")
with torch.no_grad():
logits = cross_encoder(**tokens).logits
scores = logits.reshape(-1).tolist()
documents = sorted(zip(documents, scores), key=lambda x: x[1], reverse=True)
return [doc[0] for doc in documents[:k]]
def retrieve(query, top_k_retriever=25, use_reranking=True, top_k_reranker=5):
query_vec = retriever.encode(query)
try:
documents = TABLE.search(query_vec, vector_column_name=VECTOR_COLUMN).limit(top_k_retriever).to_list()
documents = [doc[TEXT_COLUMN] for doc in documents]
if use_reranking:
documents = rerank(query, documents, top_k_reranker)
return documents
except Exception as e:
raise gr.Error(str(e))
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