Haystack docs home page


The Classifier Node is a transformer based classification model used to create predictions that can be attached to retrieved documents as metadata. For example, by using a sentiment model, you can label each document as being either positive or negative in sentiment. Through a tight integration with the HuggingFace model hub, you can easily load any classification model by simply supplying the model name.


Note that the Classifier is different from the Query Classifier. While the Query Classifier categorizes incoming queries in order to route them to different parts of the pipeline, the Classifier is used to create classification labels that can be attached to retrieved documents as metadata.


Initialize it as follows:

from haystack.classifier import FARMClassifier
classifier_model = 'textattack/bert-base-uncased-imdb'
classifier = FARMClassifier(model_name_or_path=classifier_model)

It slotted into a pipeline as follows:

pipeline = Pipeline()
pipeline.add_node(component=retriever, name="Retriever", inputs=["Query"])
pipeline.add_node(component=classifier, name='Classifier', inputs=['Retriever'])

It can also be run in isolation:

documents = classifier.predict(
documents = [doc1, doc2, doc3, ...]