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Add start index to metadata in TextSplitter (#5912)

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#### Add start index to metadata in TextSplitter

- Modified method `create_documents` to track start position of each
chunk
- The `start_index` is included in the metadata if the `add_start_index`
parameter in the class constructor is set to `True`

This enables referencing back to the original document, particularly
useful when a specific chunk is retrieved.

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#### Who can review?

Tag maintainers/contributors who might be interested:
@eyurtsev @agola11
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This commit is contained in:
felpigeon 2023-06-09 02:09:32 -04:00 committed by GitHub
parent a09a0e3511
commit 2791a753bf
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 30 additions and 7 deletions
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10
docs/modules/indexes/text_splitters/getting_started.ipynb
View File

@ -12,7 +12,8 @@
"\n",
"- `length_function`: how the length of chunks is calculated. Defaults to just counting number of characters, but it's pretty common to pass a token counter here.\n",
"- `chunk_size`: the maximum size of your chunks (as measured by the length function).\n",
"- `chunk_overlap`: the maximum overlap between chunks. It can be nice to have some overlap to maintain some continuity between chunks (eg do a sliding window)."
"- `chunk_overlap`: the maximum overlap between chunks. It can be nice to have some overlap to maintain some continuity between chunks (eg do a sliding window).\n",
"- `add_start_index` : wether to include the starting position of each chunk within the original document in the metadata. "
]
},
{
@ -49,6 +50,7 @@
" chunk_size = 100,\n",
" chunk_overlap = 20,\n",
" length_function = len,\n",
" add_start_index = True,\n",
")"
]
},
@ -62,8 +64,8 @@
"name": "stdout",
"output_type": "stream",
"text": [
"page_content='Madam Speaker, Madam Vice President, our First Lady and Second Gentleman. Members of Congress and' lookup_str='' metadata={} lookup_index=0\n",
"page_content='of Congress and the Cabinet. Justices of the Supreme Court. My fellow Americans.' lookup_str='' metadata={} lookup_index=0\n"
"page_content='Madam Speaker, Madam Vice President, our First Lady and Second Gentleman. Members of Congress and' metadata={'start_index': 0}\n",
"page_content='of Congress and the Cabinet. Justices of the Supreme Court. My fellow Americans.' metadata={'start_index': 82}\n"
]
}
],
@ -90,7 +92,7 @@
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython3",
"version": "3.9.1"
"version": "3.9.16"
},
"vscode": {
"interpreter": {

12
langchain/text_splitter.py
View File

@ -58,6 +58,7 @@ class TextSplitter(BaseDocumentTransformer, ABC):
chunk_overlap: int = 200,
length_function: Callable[[str], int] = len,
keep_separator: bool = False,
add_start_index: bool = False,
):
"""Create a new TextSplitter.
@ -66,6 +67,7 @@ class TextSplitter(BaseDocumentTransformer, ABC):
chunk_overlap: Overlap in characters between chunks
length_function: Function that measures the length of given chunks
keep_separator: Whether or not to keep the separator in the chunks
add_start_index: If `True`, includes chunk's start index in metadata
"""
if chunk_overlap > chunk_size:
raise ValueError(
@ -76,6 +78,7 @@ class TextSplitter(BaseDocumentTransformer, ABC):
self._chunk_overlap = chunk_overlap
self._length_function = length_function
self._keep_separator = keep_separator
self._add_start_index = add_start_index
@abstractmethod
def split_text(self, text: str) -> List[str]:
@ -88,10 +91,13 @@ class TextSplitter(BaseDocumentTransformer, ABC):
_metadatas = metadatas or [{}] * len(texts)
documents = []
for i, text in enumerate(texts):
index = -1
for chunk in self.split_text(text):
new_doc = Document(
page_content=chunk, metadata=copy.deepcopy(_metadatas[i])
)
metadata = copy.deepcopy(_metadatas[i])
if self._add_start_index:
index = text.find(chunk, index + 1)
metadata["start_index"] = index
new_doc = Document(page_content=chunk, metadata=metadata)
documents.append(new_doc)
return documents

15
tests/unit_tests/test_text_splitter.py
View File

@ -118,6 +118,21 @@ def test_create_documents_with_metadata() -> None:
assert docs == expected_docs
def test_create_documents_with_start_index() -> None:
"""Test create documents method."""
texts = ["foo bar baz 123"]
splitter = CharacterTextSplitter(
separator=" ", chunk_size=7, chunk_overlap=3, add_start_index=True
)
docs = splitter.create_documents(texts)
expected_docs = [
Document(page_content="foo bar", metadata={"start_index": 0}),
Document(page_content="bar baz", metadata={"start_index": 4}),
Document(page_content="baz 123", metadata={"start_index": 8}),
]
assert docs == expected_docs
def test_metadata_not_shallow() -> None:
"""Test that metadatas are not shallow."""
texts = ["foo bar"]