DocumentLanguageClassifier

Classify documents by language and add the language to the document's metadata.

Key Features

• Detects the language of each document using the langdetect library
• Adds a language metadata field with the ISO language code to each document
• Supports all languages available in langdetect
• Marks documents in languages not included in the configured list as unmatched
• Defaults to English (en) when no languages are specified
• Works well with MetadataRouter for language-based document routing

Configuration

1. Drag the DocumentLanguageClassifier component onto the canvas from the Component Library.
2. Click the component to open the configuration panel.
3. Configure the parameters as needed. Pass a list of ISO language codes you want the component to classify your documents by. If a language is not included in the list, documents in that language are classified as unmatched.

Connections

DocumentLanguageClassifier accepts a list of documents as input. It outputs the same documents with an added language metadata field. It typically receives documents from converters such as TextFileToDocument and sends classified documents to MetadataRouter, which routes them further down the pipeline based on their language. It can also connect to any component that outputs or accepts documents.

Usage Example

Using the Component in an Index

In this index, DocumentLanguageClassifier sends classified documents to MetadataRouter. MetadataRouter then routes English documents to a different document store than the German documents.

components:
  DocumentLanguageClassifier:
    type: haystack.components.classifiers.document_language_classifier.DocumentLanguageClassifier
    init_parameters:
      languages:
  TextFileToDocument:
    type: haystack.components.converters.txt.TextFileToDocument
    init_parameters:
      encoding: utf-8
      store_full_path: false
  MetadataRouter:
    type: haystack.components.routers.metadata_router.MetadataRouter
    init_parameters:
      rules:
        english:
          operator: OR
          conditions:
          - field: language
            operator: ==
            value: en
        german:
          operator: OR
          conditions:
          - field: language
            operator: ==
            value: de
  DocumentWriter_English:
    type: haystack.components.writers.document_writer.DocumentWriter
    init_parameters:
      policy: NONE
      document_store:
        type: haystack_integrations.document_stores.opensearch.document_store.OpenSearchDocumentStore
        init_parameters:
          hosts:
          index: ''
          max_chunk_bytes: 104857600
          embedding_dim: 768
          return_embedding: false
          method:
          mappings:
          settings:
          create_index: true
          http_auth:
          use_ssl:
          verify_certs:
          timeout:
  DocumentWriter_German:
    type: haystack.components.writers.document_writer.DocumentWriter
    init_parameters:
      policy: NONE
      document_store:
        type: haystack.document_stores.in_memory.document_store.InMemoryDocumentStore
        init_parameters:
          bm25_tokenization_regex: (?u)\b\w\w+\b
          bm25_algorithm: BM25L
          bm25_parameters:
          embedding_similarity_function: dot_product
          index: ''
          async_executor:

connections:  # Defines how the components are connected
- sender: TextFileToDocument.documents
  receiver: DocumentLanguageClassifier.documents
- sender: DocumentLanguageClassifier.documents
  receiver: MetadataRouter.documents
- sender: MetadataRouter.english
  receiver: DocumentWriter_English.documents
- sender: MetadataRouter.german
  receiver: DocumentWriter_German.documents

inputs:  # Define the inputs for your pipeline
  files:
  - TextFileToDocument.sources

max_runs_per_component: 100

metadata: {}

Parameters

Inputs

Parameter	Type	Default	Description
documents	List[Document]		A list of documents for language classification.

Outputs

Parameter	Type	Default	Description
documents	List[Document]		A list of documents with an added language metadata field.

Init Parameters

These are the parameters you can configure in Pipeline Builder:

Parameter	Type	Default	Description
languages	Optional[List[str]]	None	A list of ISO language codes you want to classify your documents by. For a list of supported languages, see the langdetect documentation. If not specified, defaults to ["en"].

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 for language classification.