AnswerJoiner

Merge multiple lists of Answer objects into a single list.

Basic Information

• Type: haystack.components.joiners.answer_joiner.AnswerJoiner
• Components it can connect with:
  • AnswerBuilder: Receives answers from multiple answer builders to combine their outputs.
  • Output: Sends the merged answers to the Output component.

Inputs

Parameter	Type	Default	Description
answers	Variadic[List[AnswerType]]		Nested list of Answers to be merged.
top_k	Optional[int]	None	The maximum number of Answers to return. Overrides the instance's top_k if provided.

Outputs

Parameter	Type	Default	Description
answers	List[AnswerType]		A dictionary with the following keys: - answers: Merged list of Answers

Overview

AnswerJoiner merges multiple lists of Answer objects into a single list. Use this component to combine answers from different generators into a unified output.

Currently, the component supports the CONCATENATE join mode, which concatenates multiple lists of answers into a single list.

Usage Example

This example shows a pipeline that generates answers from multiple sources and joins them.

components:
  PromptBuilder1:
    type: haystack.components.builders.prompt_builder.PromptBuilder
    init_parameters:
      template: "Answer this question briefly: {{ query }}"
  PromptBuilder2:
    type: haystack.components.builders.prompt_builder.PromptBuilder
    init_parameters:
      template: "Provide a detailed answer to: {{ query }}"
  Generator1:
    type: haystack.components.generators.openai.OpenAIGenerator
    init_parameters:
      api_key:
        type: env_var
        env_vars:
        - OPENAI_API_KEY
        strict: false
      model: gpt-4o-mini
  Generator2:
    type: haystack.components.generators.openai.OpenAIGenerator
    init_parameters:
      api_key:
        type: env_var
        env_vars:
        - OPENAI_API_KEY
        strict: false
      model: gpt-4o-mini
  AnswerBuilder1:
    type: haystack.components.builders.answer_builder.AnswerBuilder
    init_parameters:
      pattern:
      reference_pattern:
      last_message_only: false
      return_only_referenced_documents: true
  AnswerBuilder2:
    type: haystack.components.builders.answer_builder.AnswerBuilder
    init_parameters:
      pattern:
      reference_pattern:
      last_message_only: false
      return_only_referenced_documents: true
  AnswerJoiner:
    type: haystack.components.joiners.answer_joiner.AnswerJoiner
    init_parameters:
      join_mode: concatenate
      sort_by_score: false

connections:
- sender: PromptBuilder1.prompt
  receiver: Generator1.prompt
- sender: PromptBuilder2.prompt
  receiver: Generator2.prompt
- sender: Generator1.replies
  receiver: AnswerBuilder1.replies
- sender: Generator2.replies
  receiver: AnswerBuilder2.replies
- sender: AnswerBuilder1.answers
  receiver: AnswerJoiner.answers
- sender: AnswerBuilder2.answers
  receiver: AnswerJoiner.answers

max_runs_per_component: 100

metadata: {}

inputs:
  query:
  - PromptBuilder1.query
  - PromptBuilder2.query
  - AnswerBuilder1.query
  - AnswerBuilder2.query

outputs:
  answers: AnswerJoiner.answers

Parameters

Init Parameters

These are the parameters you can configure in Pipeline Builder:

Parameter	Type	Default	Description
join_mode	Union[str, JoinMode]	JoinMode.CONCATENATE	Specifies the join mode to use. Available modes: - concatenate: Concatenates multiple lists of Answers into a single list.
top_k	Optional[int]	None	The maximum number of Answers to return.
sort_by_score	bool	False	If True, sorts the documents by score in descending order. If a document has no score, it is handled as if its score is -infinity.

Run Method Parameters

These are the parameters you can configure for the component's run() method. This means you can pass these parameters at query time through the API, in Playground, or when running a job. For details, see Modify Pipeline Parameters at Query Time.

Parameter	Type	Default	Description
answers	Variadic[List[AnswerType]]		Nested list of Answers to be merged.
top_k	Optional[int]	None	The maximum number of Answers to return. Overrides the instance's top_k if provided.