---
title: "FAISSEmbeddingRetriever"
id: faissembeddingretriever
slug: "/faissembeddingretriever"
description: "An embedding-based Retriever compatible with the FAISSDocumentStore."
---

# FAISSEmbeddingRetriever

An embedding-based Retriever compatible with the FAISSDocumentStore.

<div className="key-value-table">

|  |  |
| --- | --- |
| **Most common position in a pipeline** | 1. After a Text Embedder and before a [`PromptBuilder`](../builders/promptbuilder.mdx) in a RAG pipeline 2. The last component in a semantic search pipeline 3. After a Text Embedder and before an [`ExtractiveReader`](../readers/extractivereader.mdx) in an extractive QA pipeline |
| **Mandatory init variables**           | `document_store`: An instance of a [`FAISSDocumentStore`](../../document-stores/faissdocumentstore.mdx) |
| **Mandatory run variables**            | `query_embedding`: A vector representing the query (a list of floats) |
| **Output variables**                   | `documents`: A list of documents |
| **API reference**                      | [FAISS](/reference/integrations-faiss) |
| **GitHub link**                        | https://github.com/deepset-ai/haystack-core-integrations/tree/main/integrations/faiss |
| **Package name** | `faiss-haystack` |

</div>

## Overview

The `FAISSEmbeddingRetriever` is an embedding-based Retriever that queries a `FAISSDocumentStore`. It compares the query embedding to document embeddings stored in FAISS and returns the most similar documents.

This Retriever expects precomputed embeddings in the Document Store and a query embedding at runtime. You can generate them with a Document Embedder in your indexing pipeline and a Text Embedder in your query pipeline.

In addition to `query_embedding`, you can pass:

- `top_k`: The maximum number of documents to return.
- `filters`: Metadata filters to restrict retrieved documents.

You can also configure default filters and `filter_policy` at initialization.

## Usage

### On its own

```python
from haystack_integrations.document_stores.faiss import FAISSDocumentStore
from haystack_integrations.components.retrievers.faiss import FAISSEmbeddingRetriever

document_store = FAISSDocumentStore(embedding_dim=768)
retriever = FAISSEmbeddingRetriever(document_store=document_store, top_k=5)

# Example query embedding
result = retriever.run(query_embedding=[0.1] * 768)
print(result["documents"])
```

### In a pipeline

```python
from haystack import Document, Pipeline
from haystack.components.embedders import (
    SentenceTransformersDocumentEmbedder,
    SentenceTransformersTextEmbedder,
)
from haystack.document_stores.types import DuplicatePolicy
from haystack_integrations.document_stores.faiss import FAISSDocumentStore
from haystack_integrations.components.retrievers.faiss import FAISSEmbeddingRetriever

document_store = FAISSDocumentStore(embedding_dim=768)

documents = [
    Document(content="There are over 7,000 languages spoken around the world today."),
    Document(
        content="Elephants have been observed to behave in a way that indicates a high level of intelligence.",
    ),
    Document(
        content="In certain places, you can witness the phenomenon of bioluminescent waves.",
    ),
]

document_embedder = SentenceTransformersDocumentEmbedder()
documents_with_embeddings = document_embedder.run(documents)["documents"]
document_store.write_documents(
    documents_with_embeddings,
    policy=DuplicatePolicy.OVERWRITE,
)

query_pipeline = Pipeline()
query_pipeline.add_component("text_embedder", SentenceTransformersTextEmbedder())
query_pipeline.add_component(
    "retriever",
    FAISSEmbeddingRetriever(document_store=document_store),
)
query_pipeline.connect("text_embedder.embedding", "retriever.query_embedding")

query = "How many languages are there?"
result = query_pipeline.run({"text_embedder": {"text": query}})

print(result["retriever"]["documents"][0])
```
