refactor: simplify Summarizer, add Document Merger

docs/_src/api/pydoc/other.yml

@@ -1,7 +1,7 @@
 loaders:
   - type: python
     search_path: [../../../../haystack/nodes/other]
-    modules: ['docs2answers', 'join_docs', 'join_answers', 'route_documents']
+    modules: ['docs2answers', 'join_docs', 'join_answers', 'route_documents', 'document_merger']
     ignore_when_discovered: ['__init__']
 processors:
   - type: filter

haystack/nodes/other/document_merger.py

@@ -0,0 +1,88 @@
+import logging
+from copy import deepcopy
+from typing import Optional, List, Dict, Union, Any
+
+from haystack.schema import Document
+from haystack.nodes.base import BaseComponent
+
+logger = logging.getLogger(__name__)
+
+
+class DocumentMerger(BaseComponent):
+    """
+    A node to merge the texts of the documents.
+    """
+
+    outgoing_edges = 1
+
+    def __init__(self, separator: str = " "):
+        """
+        :param separator: The separator that appears between subsequent merged documents.
+        """
+        super().__init__()
+        self.separator = separator
+
+    def merge(self, documents: List[Document], separator: Optional[str] = None) -> List[Document]:
+        """
+        Produce a list made up of a single document, which contains all the texts of the documents provided.
+
+        :param separator: The separator that appears between subsequent merged documents.
+        :return: List of Documents
+        """
+        if len(documents) == 0:
+            raise ValueError("Document Merger needs at least one document to merge.")
+        if not all(doc.content_type == "text" for doc in documents):
+            raise ValueError(
+                "Some of the documents provided are non-textual. Document Merger only works on textual documents."
+            )
+
+        separator = separator if separator is not None else self.separator
+
+        merged_content = separator.join([doc.content for doc in documents])
+        common_meta = self._keep_common_keys([doc.meta for doc in documents])
+
+        merged_document = Document(content=merged_content, meta=common_meta)
+        return [merged_document]
+
+    def run(self, documents: List[Document], separator: Optional[str] = None):  # type: ignore
+        results: Dict = {"documents": []}
+        if documents:
+            results["documents"] = self.merge(documents=documents, separator=separator)
+        return results, "output_1"
+
+    def run_batch(  # type: ignore
+        self, documents: Union[List[Document], List[List[Document]]], separator: Optional[str] = None
+    ):
+        is_doclist_flat = isinstance(documents[0], Document)
+        if is_doclist_flat:
+            flat_result: List[Document] = self.merge(
+                documents=[doc for doc in documents if isinstance(doc, Document)], separator=separator
+            )
+            return {"documents": flat_result}, "output_1"
+        else:
+            nested_result: List[List[Document]] = [
+                self.merge(documents=docs_lst, separator=separator)
+                for docs_lst in documents
+                if isinstance(docs_lst, list)
+            ]
+            return {"documents": nested_result}, "output_1"
+
+    def _keep_common_keys(self, list_of_dicts: List[Dict[str, Any]]) -> dict:
+        merge_dictionary = deepcopy(list_of_dicts[0])
+        for key, value in list_of_dicts[0].items():
+
+            # if not all other dicts have this key, delete directly
+            if not all(key in dict.keys() for dict in list_of_dicts):
+                del merge_dictionary[key]
+
+            # if they all have it and it's a dictionary, merge recursively
+            elif isinstance(value, dict):
+                # Get all the subkeys to merge in a new list
+                list_of_subdicts = [dictionary[key] for dictionary in list_of_dicts]
+                merge_dictionary[key] = self._keep_common_keys(list_of_subdicts)
+
+            # If all dicts have this key and it's not a dictionary, delete only if the values differ
+            elif not all(value == dict[key] for dict in list_of_dicts):
+                del merge_dictionary[key]
+
+        return merge_dictionary

haystack/nodes/summarizer/base.py

@@ -19,12 +19,8 @@ def predict(self, documents: List[Document], generate_single_summary: Optional[b
         Abstract method for creating a summary.
 
         :param documents: Related documents (e.g. coming from a retriever) that the answer shall be conditioned on.
-        :param generate_single_summary: Whether to generate a single summary for all documents or one summary per document.
-                                        If set to "True", all docs will be joined to a single string that will then
-                                        be summarized.
-                                        Important: The summary will depend on the order of the supplied documents!
-        :return: List of Documents, where Document.content contains the summarization and Document.meta["context"]
-                 the original, not summarized text
+        :param generate_single_summary: This parameter is deprecated and will be removed in Haystack 1.12
+        :return: List of Documents, where Document.meta["summary"] contains the summarization
         """
         pass
 
@@ -54,7 +50,7 @@ def run_batch(  # type: ignore
     ):
 
         results = self.predict_batch(
-            documents=documents, generate_single_summary=generate_single_summary, batch_size=batch_size
+            documents=documents, batch_size=batch_size, generate_single_summary=generate_single_summary
         )
 
         return {"documents": results}, "output_1"

haystack/nodes/summarizer/transformers.py

@@ -6,7 +6,6 @@
 import torch
 from tqdm.auto import tqdm
 from transformers import pipeline
-from transformers.models.auto.modeling_auto import AutoModelForSeq2SeqLM
 
 from haystack.schema import Document
 from haystack.nodes.summarizer.base import BaseSummarizer
@@ -34,19 +33,18 @@ class TransformersSummarizer(BaseSummarizer):
     |
     |     # Summarize
     |     summary = summarizer.predict(
-    |        documents=docs,
-    |        generate_single_summary=True
-    |     )
+    |        documents=docs)
     |
-    |     # Show results (List of Documents, containing summary and original text)
+    |     # Show results (List of Documents, containing summary and original content)
     |     print(summary)
     |
     |    [
     |      {
-    |        "text": "California's largest electricity provider has turned off power to hundreds of thousands of customers.",
+    |        "content": "PGE stated it scheduled the blackouts in response to forecasts for high winds amid dry conditions. ...",
     |        ...
     |        "meta": {
-    |          "context": "PGE stated it scheduled the blackouts in response to forecasts for high winds amid dry conditions. ..."
+    |                   "summary": "California's largest electricity provider has turned off power to hundreds of thousands of customers.",
+    |                   ...
     |              },
     |        ...
     |      },
@@ -83,12 +81,9 @@ def __init__(
         :param min_length: Minimum length of summarized text
         :param use_gpu: Whether to use GPU (if available).
         :param clean_up_tokenization_spaces: Whether or not to clean up the potential extra spaces in the text output
-        :param separator_for_single_summary: If `generate_single_summary=True` in `predict()`, we need to join all docs
-                                             into a single text. This separator appears between those subsequent docs.
-        :param generate_single_summary: Whether to generate a single summary for all documents or one summary per document.
-                                        If set to "True", all docs will be joined to a single string that will then
-                                        be summarized.
-                                        Important: The summary will depend on the order of the supplied documents!
+        :param separator_for_single_summary: This parameter is deprecated and will be removed in Haystack 1.12
+        :param generate_single_summary: This parameter is deprecated and will be removed in Haystack 1.12.
+                                        To obtain single summaries from multiple documents, consider using the [DocumentMerger](https://docs.haystack.deepset.ai/docs/document_merger).
         :param batch_size: Number of documents to process at a time.
         :param progress_bar: Whether to show a progress bar.
         :param use_auth_token: The API token used to download private models from Huggingface.
@@ -103,27 +98,32 @@ def __init__(
         """
         super().__init__()
 
+        if generate_single_summary is True:
+            raise ValueError(
+                "'generate_single_summary' has been removed. Instead, you can use the Document Merger to merge documents before applying the Summarizer."
+            )
+
         self.devices, _ = initialize_device_settings(devices=devices, use_cuda=use_gpu, multi_gpu=False)
         if len(self.devices) > 1:
             logger.warning(
                 f"Multiple devices are not supported in {self.__class__.__name__} inference, "
                 f"using the first device {self.devices[0]}."
             )
 
-        # TODO AutoModelForSeq2SeqLM is only necessary with transformers==4.1.1, with newer versions use the pipeline directly
         if tokenizer is None:
             tokenizer = model_name_or_path
-        model = AutoModelForSeq2SeqLM.from_pretrained(
-            pretrained_model_name_or_path=model_name_or_path, revision=model_version, use_auth_token=use_auth_token
-        )
+
         self.summarizer = pipeline(
-            "summarization", model=model, tokenizer=tokenizer, device=self.devices[0], use_auth_token=use_auth_token
+            task="summarization",
+            model=model_name_or_path,
+            tokenizer=tokenizer,
+            revision=model_version,
+            device=self.devices[0],
+            use_auth_token=use_auth_token,
         )
         self.max_length = max_length
         self.min_length = min_length
         self.clean_up_tokenization_spaces = clean_up_tokenization_spaces
-        self.separator_for_single_summary = separator_for_single_summary
-        self.generate_single_summary = generate_single_summary
         self.print_log: Set[str] = set()
         self.batch_size = batch_size
         self.progress_bar = progress_bar
@@ -134,29 +134,23 @@ def predict(self, documents: List[Document], generate_single_summary: Optional[b
         These document can for example be retrieved via the Retriever.
 
         :param documents: Related documents (e.g. coming from a retriever) that the answer shall be conditioned on.
-        :param generate_single_summary: Whether to generate a single summary for all documents or one summary per document.
-                                        If set to "True", all docs will be joined to a single string that will then
-                                        be summarized.
-                                        Important: The summary will depend on the order of the supplied documents!
-        :return: List of Documents, where Document.text contains the summarization and Document.meta["context"]
-                 the original, not summarized text
+        :param generate_single_summary: This parameter is deprecated and will be removed in Haystack 1.12.
+                                        To obtain single summaries from multiple documents, consider using the [DocumentMerger](https://docs.haystack.deepset.ai/docs/document_merger).
+        :return: List of Documents, where Document.meta["summary"] contains the summarization
         """
+        if generate_single_summary is True:
+            raise ValueError(
+                "'generate_single_summary' has been removed. Instead, you can use the Document Merger to merge documents before applying the Summarizer."
+            )
+
         if self.min_length > self.max_length:
             raise AttributeError("min_length cannot be greater than max_length")
 
         if len(documents) == 0:
             raise AttributeError("Summarizer needs at least one document to produce a summary.")
 
-        if generate_single_summary is None:
-            generate_single_summary = self.generate_single_summary
-
         contexts: List[str] = [doc.content for doc in documents]
 
-        if generate_single_summary:
-            # Documents order is very important to produce summary.
-            # Different order of same documents produce different summary.
-            contexts = [self.separator_for_single_summary.join(contexts)]
-
         encoded_input = self.summarizer.tokenizer(contexts, verbose=False)
         for input_id in encoded_input["input_ids"]:
             tokens_count: int = len(input_id)
@@ -182,15 +176,9 @@ def predict(self, documents: List[Document], generate_single_summary: Optional[b
 
         result: List[Document] = []
 
-        if generate_single_summary:
-            for context, summarized_answer in zip(contexts, summaries):
-                cur_doc = Document(content=summarized_answer["summary_text"], meta={"context": context})
-                result.append(cur_doc)
-        else:
-            for context, summarized_answer, document in zip(contexts, summaries, documents):
-                cur_doc = Document(content=summarized_answer["summary_text"], meta=document.meta)
-                cur_doc.meta.update({"context": context})
-                result.append(cur_doc)
+        for summary, document in zip(summaries, documents):
+            document.meta.update({"summary": summary["summary_text"]})
+            result.append(document)
 
         return result
 
@@ -206,13 +194,14 @@ def predict_batch(
 
         :param documents: Single list of related documents or list of lists of related documents
                           (e.g. coming from a retriever) that the answer shall be conditioned on.
-        :param generate_single_summary: Whether to generate a single summary for each provided document list or
-                                        one summary per document.
-                                        If set to "True", all docs of a document list will be joined to a single string
-                                        that will then be summarized.
-                                        Important: The summary will depend on the order of the supplied documents!
+        :param generate_single_summary: This parameter is deprecated and will be removed in Haystack 1.12.
+                                        To obtain single summaries from multiple documents, consider using the [DocumentMerger](https://docs.haystack.deepset.ai/docs/document_merger).
         :param batch_size: Number of Documents to process at a time.
         """
+        if generate_single_summary is True:
+            raise ValueError(
+                "'generate_single_summary' has been removed. Instead, you can use the Document Merger to merge documents before applying the Summarizer."
+            )
 
         if self.min_length > self.max_length:
             raise AttributeError("min_length cannot be greater than max_length")
@@ -225,34 +214,17 @@ def predict_batch(
         if batch_size is None:
             batch_size = self.batch_size
 
-        if generate_single_summary is None:
-            generate_single_summary = self.generate_single_summary
-
-        single_doc_list = False
-        if isinstance(documents[0], Document):
-            single_doc_list = True
-
-        if single_doc_list:
+        is_doclist_flat = isinstance(documents[0], Document)
+        if is_doclist_flat:
             contexts = [doc.content for doc in documents if isinstance(doc, Document)]
         else:
             contexts = [
                 [doc.content for doc in docs if isinstance(doc, Document)]
                 for docs in documents
                 if isinstance(docs, list)
             ]
-
-        if generate_single_summary:
-            if single_doc_list:
-                contexts = [self.separator_for_single_summary.join(contexts)]
-            else:
-                contexts = [self.separator_for_single_summary.join(context_group) for context_group in contexts]
-            number_of_docs = [1 for _ in contexts]
-        else:
-            if single_doc_list:
-                number_of_docs = [1 for _ in contexts]
-            else:
-                number_of_docs = [len(context_group) for context_group in contexts]
-                contexts = list(itertools.chain.from_iterable(contexts))
+            number_of_docs = [len(context_group) for context_group in contexts]
+            contexts = list(itertools.chain.from_iterable(contexts))
 
         encoded_input = self.summarizer.tokenizer(contexts, verbose=False)
         for input_id in encoded_input["input_ids"]:
@@ -286,26 +258,30 @@ def predict_batch(
         ):
             summaries.extend(summary_batch)
 
-        # Group summaries together
-        grouped_summaries = []
-        grouped_contexts = []
-        left_idx = 0
-        right_idx = 0
-        for number in number_of_docs:
-            right_idx = left_idx + number
-            grouped_summaries.append(summaries[left_idx:right_idx])
-            grouped_contexts.append(contexts[left_idx:right_idx])
-            left_idx = right_idx
-
-        result = []
-        for summary_group, context_group in zip(grouped_summaries, grouped_contexts):
-            cur_summaries = [
-                Document(content=summary["summary_text"], meta={"context": context})
-                for summary, context in zip(summary_group, context_group)
-            ]
-            if single_doc_list:
-                result.append(cur_summaries[0])
-            else:
-                result.append(cur_summaries)  # type: ignore
-
-        return result
+        if is_doclist_flat:
+            flat_result: List[Document] = []
+            flat_doc_list: List[Document] = [doc for doc in documents if isinstance(doc, Document)]
+            for summary, document in zip(summaries, flat_doc_list):
+                document.meta.update({"summary": summary["summary_text"]})
+                flat_result.append(document)
+            return flat_result
+        else:
+            nested_result: List[List[Document]] = []
+            nested_doc_list: List[List[Document]] = [lst for lst in documents if isinstance(lst, list)]
+
+            # Group summaries together
+            grouped_summaries = []
+            left_idx = 0
+            right_idx = 0
+            for number in number_of_docs:
+                right_idx = left_idx + number
+                grouped_summaries.append(summaries[left_idx:right_idx])
+                left_idx = right_idx
+
+            for summary_group, docs_group in zip(grouped_summaries, nested_doc_list):
+                cur_summaries = []
+                for summary, document in zip(summary_group, docs_group):
+                    document.meta.update({"summary": summary["summary_text"]})
+                    cur_summaries.append(document)
+                nested_result.append(cur_summaries)
+            return nested_result