MetadataRouter

Route documents or byte streams to different pipeline branches based on their metadata fields.

Key Features

• Routes documents or byte streams based on metadata filtering rules.
• Supports complex conditions using Haystack's metadata filtering syntax (AND, OR, and comparison operators).
• Routes unmatched items to a dedicated unmatched output.
• Can handle both Document and ByteStream objects in the same configuration.

Configuration

1. Drag the MetadataRouter component onto the canvas from the Component Library.
2. Click on the component to open the configuration panel.
3. On the General tab:
   • Set the Rules dictionary. Keys are output connection names and values are metadata filtering expressions. Items matching a rule go to that named output. Items not matching any rule go to unmatched.
   • Set the Output Type to documents or byte_streams depending on what you're routing (default is documents).

Connections

MetadataRouter receives either a List[Document] or a List[ByteStream] depending on the configured output type. For each rule you define, it creates a named output connection. Items that don't match any rule go to the unmatched output. Connect each named output to the appropriate downstream component.

Source Code

To check this component's source code, open metadata_router.py in the Haystack repository.

Usage Examples

Basic Configuration

  MetadataRouter:
    type: components.routers.metadata_router.MetadataRouter
    init_parameters:
      output_type: documents
      rules:
        edge_1:
          operator: AND
          conditions:
          - field: meta.created_at
            operator: '>='
            value: '2023-01-01'
          - field: meta.created_at
            operator: <
            value: '2023-04-01'

components:
  MetadataRouter:
    type: components.routers.metadata_router.MetadataRouter
    init_parameters:
      output_type: documents  # or byte_streams
      rules:
        edge_1:
          operator: AND
          conditions:
          - field: meta.created_at
            operator: ">="
            value: "2023-01-01"
          - field: meta.created_at
            operator: "<"
            value: "2023-04-01"

Parameters

Inputs

Parameter	Type	Description
documents	List[Document]	A list of documents to route.
byte_streams	List[ByteStream]	A list of byte streams to route.

Outputs

Parameter	Type	Description
(per rule name)	List[Document] or List[ByteStream]	Items matching the corresponding rule.
unmatched	List[Document] or List[ByteStream]	Items that don't match any rule.

Init Parameters

These are the parameters you can configure in Pipeline Builder:

Parameter	Type	Default	Description
rules	Dict[str, Dict]		A dictionary defining routing rules. Keys are output connection names and values are metadata filtering expressions. For example: {"edge_1": {"operator": "AND", "conditions": [{"field": "meta.created_at", "operator": ">=", "value": "2023-01-01"}]}}. Items not matching any rule go to unmatched.
output_type	Optional[str]	documents	The type of objects to route. Can be documents or byte_streams.

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
documents	List[Document]		A list of documents to route.
byte_streams	List[ByteStream]		A list of byte streams to route.