Watsonx Reranker

This reranker uses the IBM watsonx.ai text rerank API to reorder search results. Pass WatsonxReranker() to the rerank() method on a query. Credentials come from the WATSONX_API_KEY and WATSONX_PROJECT_ID (or WATSONX_SPACE_ID) environment variables, or can be passed explicitly as arguments.

Note: Supported query types – Hybrid, Vector, and FTS.

pip install ibm-watsonx-ai

Accepted Arguments

Argument	Type	Default	Description
`model_name`	`str`	`"cross-encoder/ms-marco-minilm-l-12-v2"`	The rerank model ID. See supported rerank models.
`column`	`str`	`"text"`	The name of the table column to use as document input.
`top_n`	`int`	`None`	The number of results to return. If `None`, all results are returned.
`return_score`	`str`	`"relevance"`	Options are `"relevance"` or `"all"`. Controls which score columns are kept on the result.
`api_key`	`str`	`None`	IBM Cloud API key. Falls back to the `WATSONX_API_KEY` environment variable.
`project_id`	`str`	`None`	watsonx.ai project ID. Falls back to `WATSONX_PROJECT_ID`. Mutually exclusive with `space_id`.
`space_id`	`str`	`None`	watsonx.ai deployment space ID. Falls back to `WATSONX_SPACE_ID`. Mutually exclusive with `project_id`.
`url`	`str`	`"https://us-south.ml.cloud.ibm.com"`	watsonx.ai service URL.
`truncate_input_tokens`	`int`	`None`	Truncate each document to this many tokens before scoring.

You must supply exactly one of project_id or space_id (either as an argument or via its environment variable). Setting both, or neither, raises a ValueError.

Supported scores for each query type

You can specify the type of scores you want the reranker to return. The following are the supported scores for each query type:

Hybrid Search

`return_score`	Status	Description
`relevance`	✅ Supported	Results only have the `_relevance_score` column.
`all`	❌ Not Supported	Results have vector(`_distance`) and FTS(`score`) along with Hybrid Search score(`_relevance_score`).

Vector Search

`return_score`	Status	Description
`relevance`	✅ Supported	Results only have the `_relevance_score` column.
`all`	✅ Supported	Results have vector(`_distance`) along with Hybrid Search score(`_relevance_score`).

FTS Search

`return_score`	Status	Description
`relevance`	✅ Supported	Results only have the `_relevance_score` column.
`all`	✅ Supported	Results have FTS(`score`) along with Hybrid Search score(`_relevance_score`).

​Watsonx Reranker

​Accepted Arguments

​Supported scores for each query type

​Hybrid Search

​Vector Search

​FTS Search

Watsonx Reranker

Accepted Arguments

Supported scores for each query type

Hybrid Search

Vector Search

FTS Search