---
title: "OpenSearchEmbeddingRetriever"
id: opensearchembeddingretriever
slug: "/opensearchembeddingretriever"
description: "An embedding-based Retriever compatible with the OpenSearch Document Store."
---

# OpenSearchEmbeddingRetriever

An embedding-based Retriever compatible with the OpenSearch Document Store.

<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 the 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 an [OpenSearchDocumentStore](../../document-stores/opensearch-document-store.mdx)                                                                                                                                                                              |
| **Mandatory run variables**            | `query_embedding`: A list of floats                                                                                                                                                                                                                                       |
| **Output variables**                   | `documents`: A list of documents                                                                                                                                                                                                                                          |
| **API reference**                      | [OpenSearch](/reference/integrations-opensearch)                                                                                                                                                                                                                                 |
| **GitHub link**                        | https://github.com/deepset-ai/haystack-core-integrations/tree/main/integrations/opensearch                                                                                                                                                                              |

</div>

## Overview

The `OpenSearchEmbeddingRetriever` is an embedding-based Retriever compatible with the `OpenSearchDocumentStore`. It compares the query and Document embeddings and fetches the Documents most relevant to the query from the `OpenSearchDocumentStore` based on the outcome.

When using the `OpenSearchEmbeddingRetriever` in your NLP system, make sure it has the query and Document embeddings available. You can do so by adding a Document Embedder to your indexing pipeline and a Text Embedder to your query pipeline.

In addition to the `query_embedding`, the `OpenSearchEmbeddingRetriever` accepts other optional parameters, including `top_k` (the maximum number of Documents to retrieve) and `filters` to narrow down the search space.

The `embedding_dim` for storing and retrieving embeddings must be defined when the corresponding `OpenSearchDocumentStore` is initialized.

### Setup and installation

[Install](https://opensearch.org/docs/latest/install-and-configure/install-opensearch/index/) and run an OpenSearch instance.

If you have Docker set up, we recommend pulling the Docker image and running it.

```shell
docker pull opensearchproject/opensearch:2.11.0
docker run -p 9200:9200 -p 9600:9600 -e "discovery.type=single-node" -e "ES_JAVA_OPTS=-Xms1024m -Xmx1024m" opensearchproject/opensearch:2.11.0
```

As an alternative, you can go to [OpenSearch integration GitHub](https://github.com/deepset-ai/haystack-core-integrations/tree/main/integrations/opensearch) and start a Docker container running OpenSearch using the provided `docker-compose.yml`:

```shell
docker compose up
```

Once you have a running OpenSearch instance, install the `opensearch-haystack` integration:

```shell
pip install opensearch-haystack
```

## Usage

### In a pipeline

Use this Retriever in a query Pipeline like this:

```python
from haystack_integrations.components.retrievers.opensearch import (
    OpenSearchEmbeddingRetriever,
)
from haystack_integrations.document_stores.opensearch import OpenSearchDocumentStore

from haystack.document_stores.types import DuplicatePolicy
from haystack import Document
from haystack import Pipeline
from haystack.components.embedders import (
    SentenceTransformersTextEmbedder,
    SentenceTransformersDocumentEmbedder,
)

document_store = OpenSearchDocumentStore(
    hosts="http://localhost:9200",
    use_ssl=True,
    verify_certs=False,
    http_auth=("admin", "admin"),
)

model = "sentence-transformers/all-mpnet-base-v2"

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 self-awareness, such as recognizing themselves in mirrors.",
    ),
    Document(
        content="In certain parts of the world, like the Maldives, Puerto Rico, and San Diego, you can witness the phenomenon of bioluminescent waves.",
    ),
]

document_embedder = SentenceTransformersDocumentEmbedder(model=model)
document_embedder.warm_up()
documents_with_embeddings = document_embedder.run(documents)

document_store.write_documents(
    documents_with_embeddings.get("documents"),
    policy=DuplicatePolicy.SKIP,
)

query_pipeline = Pipeline()
query_pipeline.add_component(
    "text_embedder",
    SentenceTransformersTextEmbedder(model=model),
)
query_pipeline.add_component(
    "retriever",
    OpenSearchEmbeddingRetriever(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])
```

The example output would be:

```python
Document(id=cfe93bc1c274908801e6670440bf2bbba54fad792770d57421f85ffa2a4fcc94, content: 'There are over 7,000 languages spoken around the world today.', score: 0.70026743, embedding: vector of size 768)
```

## Additional References

🧑‍🍳 Cookbook: [PDF-Based Question Answering with Amazon Bedrock and Haystack](https://haystack.deepset.ai/cookbook/amazon_bedrock_for_documentation_qa)
