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Rerank processor

The rerank search request processor intercepts search results and passes them to a cross-encoder model to be reranked. The model reranks the results, taking into account the scoring context. Then the processor orders documents in the search results based on their new scores.

Request fields

The following table lists all available request fields.

The ml_opensearch reranker type

The ml_opensearch reranker type is designed to work with the cross-encoder model provided by OpenSearch. For this reranker type, specify the following fields.

Example

The following example demonstrates using a search pipeline with a rerank processor.

Creating a search pipeline

The following request creates a search pipeline with a rerank response processor:

PUT /_search/pipeline/rerank_pipeline
{
  "response_processors": [
    {
      "rerank": {
        "ml_opensearch": {
          "model_id": "gnDIbI0BfUsSoeNT_jAw"
        },
        "context": {
          "document_fields": [ "title", "text_representation"]
        }
      }
    }
  ]
}

Using a search pipeline

Combine an OpenSearch query with an ext object that contains the query context for the large language model (LLM). Provide the query_text that will be used to rerank the results:

POST /_search?search_pipeline=rerank_pipeline
{
  "query": {
    "match": {
      "text_representation": "Where is Albuquerque?"
    }
  },
  "ext": {
    "rerank": {
      "query_context": {
        "query_text": "Where is Albuquerque?"
      }
    }
  }
}

Instead of specifying query_text, you can provide a full path to the field containing text to use for reranking. For example, if you specify a subfield query in the text_representation object, specify its path in the query_text_path parameter:

POST /_search?search_pipeline=rerank_pipeline
{
  "query": {
    "match": {
      "text_representation": {
        "query": "Where is Albuquerque?"
      }
    }
  },
  "ext": {
    "rerank": {
      "query_context": {
        "query_text_path": "query.match.text_representation.query"
      }
    }
  }
}

The query_context object contains the following fields.

For more information about setting up reranking, see Reranking search results.