FAISS and ElasticSearch enables searching for examples in a dataset. This can be useful when you want to retrieve specific examples from a dataset that are relevant to your NLP task. For example, if you are working on a Open Domain Question Answering task, you may want to only return examples that are relevant to answering your question.
This guide will show you how to build an index for your dataset that will allow you to search it.
FAISS retrieves documents based on the similarity of their vector representations. In this example, you will generate the vector representations with the DPR model.
>>> from transformers import DPRContextEncoder, DPRContextEncoderTokenizer
>>> import torch
>>> torch.set_grad_enabled(False)
>>> ctx_encoder = DPRContextEncoder.from_pretrained("facebook/dpr-ctx_encoder-single-nq-base")
>>> ctx_tokenizer = DPRContextEncoderTokenizer.from_pretrained("facebook/dpr-ctx_encoder-single-nq-base")
>>> from datasets import load_dataset
>>> ds = load_dataset('crime_and_punish', split='train[:100]')
>>> ds_with_embeddings = ds.map(lambda example: {'embeddings': ctx_encoder(**ctx_tokenizer(example["line"], return_tensors="pt"))[0][0].numpy()})
>>> ds_with_embeddings.add_faiss_index(column='embeddings')
embeddings
index. Load the DPR Question Encoder, and search for a question with Dataset.get_nearest_examples():>>> from transformers import DPRQuestionEncoder, DPRQuestionEncoderTokenizer
>>> q_encoder = DPRQuestionEncoder.from_pretrained("facebook/dpr-question_encoder-single-nq-base")
>>> q_tokenizer = DPRQuestionEncoderTokenizer.from_pretrained("facebook/dpr-question_encoder-single-nq-base")
>>> question = "Is it serious ?"
>>> question_embedding = q_encoder(**q_tokenizer(question, return_tensors="pt"))[0][0].numpy()
>>> scores, retrieved_examples = ds_with_embeddings.get_nearest_examples('embeddings', question_embedding, k=10)
>>> retrieved_examples["line"][0]
'_that_ serious? It is not serious at all. It’s simply a fantasy to amuse\r\n'
range_search
:>>> faiss_index = ds_with_embeddings.get_index('embeddings').faiss_index
>>> limits, distances, indices = faiss_index.range_search(x=question_embedding.reshape(1, -1), thresh=0.95)
>>> ds_with_embeddings.save_faiss_index('embeddings', 'my_index.faiss')
>>> ds = load_dataset('crime_and_punish', split='train[:100]')
>>> ds.load_faiss_index('embeddings', 'my_index.faiss')
Unlike FAISS, ElasticSearch retrieves documents based on exact matches.
Start ElasticSearch on your machine, or see the ElasticSearch installation guide if you don’t already have it installed.
>>> from datasets import load_dataset
>>> squad = load_dataset('squad', split='validation')
>>> squad.add_elasticsearch_index("context", host="localhost", port="9200")
context
index with Dataset.get_nearest_examples():>>> query = "machine"
>>> scores, retrieved_examples = squad.get_nearest_examples("context", query, k=10)
>>> retrieved_examples["title"][0]
'Computational_complexity_theory'
es_index_name
parameter when you build the index:>>> from datasets import load_dataset
>>> squad = load_dataset('squad', split='validation')
>>> squad.add_elasticsearch_index("context", host="localhost", port="9200", es_index_name="hf_squad_val_context")
>>> squad.get_index("context").es_index_name
hf_squad_val_context
>>> from datasets import load_dataset
>>> squad = load_dataset('squad', split='validation')
>>> squad.load_elasticsearch_index("context", host="localhost", port="9200", es_index_name="hf_squad_val_context")
>>> query = "machine"
>>> scores, retrieved_examples = squad.get_nearest_examples("context", query, k=10)
For more advanced ElasticSearch usage, you can specify your own configuration with custom settings:
>>> import elasticsearch as es
>>> import elasticsearch.helpers
>>> from elasticsearch import Elasticsearch
>>> es_client = Elasticsearch([{"host": "localhost", "port": "9200"}]) # default client
>>> es_config = {
... "settings": {
... "number_of_shards": 1,
... "analysis": {"analyzer": {"stop_standard": {"type": "standard", " stopwords": "_english_"}}},
... },
... "mappings": {"properties": {"text": {"type": "text", "analyzer": "standard", "similarity": "BM25"}}},
... } # default config
>>> es_index_name = "hf_squad_context" # name of the index in ElasticSearch
>>> squad.add_elasticsearch_index("context", es_client=es_client, es_config=es_config, es_index_name=es_index_name)