Fix duplicate node positions when identical text appears multiple times in document #20050
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…es in document When parsing nodes, the _postprocess_parsed_nodes method was using parent_doc.text.find() to locate node content in the parent document. This always returns the FIRST occurrence, causing nodes with identical text from different parts of the document to be assigned the same start/end positions. This led to downstream issues where: - Multiple nodes appeared at the same position - Position-based operations (sorting, merging) behaved incorrectly - Node verification logic failed to properly handle sequential chunks Fix: Track search position per document and search from the last found position. Since _parse_nodes returns nodes in document order, this ensures each node is assigned to the correct occurrence of its text. Example bug scenario before fix: Document: 'Chapter 1\nSummary here.\nChapter 2\nSummary here.' Node 1 text: 'Summary here.' -> start_idx=10 ✓ Node 2 text: 'Summary here.' -> start_idx=10 ✗ (should be 33) After fix: Node 1 text: 'Summary here.' -> start_idx=10 ✓ Node 2 text: 'Summary here.' -> start_idx=33 ✓
Three test cases verify that: 1. Nodes with identical text get assigned to different positions 2. Mixed duplicate and unique text is handled correctly 3. Position tracking is independent per document All tests pass with the fix in _postprocess_parsed_nodes.
dosubot
bot
added
the
size:L
- Reduce test file from 251 to 70 lines - Add comprehensive validation function checking: * Valid bounds and no negative lengths * Text matches document positions * No duplicate positions for same text * Sequential ordering - Keep 3 focused test cases covering main scenarios - Tests validate the fix works correctly across different parsers
AstraBert
reviewed
Oct 10, 2025
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| # update start/end char idx | ||
| if start_char_idx >= 0 and isinstance(node, TextNode): | ||
| node.start_char_idx = start_char_idx |
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Seems like the introduced change, reflected here, causes this test failure:
FAILED tests/text_splitter/test_sentence_splitter.py::test_start_end_char_idx - AssertionError: assert None is not None
+ where None = TextNode(id_='458cccbc-ce17-498c-84d4-5b765ce44b5f', embedding=None, metadata={}, excluded_embed_metadata_keys=[], exc...t/plain', start_char_idx=None, end_char_idx=None, metadata_seperator='\n', text_template='{metadata_str}\n\n{content}').start_char_idx
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Thanks for catching that! The issue was with overlapping chunks - my initial implementation tracked search position to the end of each node, which skipped over overlapping content when chunk_overlap > 0.
I've updated the fix to track start_char_idx + 1 instead of end_char_idx, which allows overlapping chunks to be found while still fixing the duplicate text bug.
All tests now pass, including test_start_end_char_idx.
The previous implementation tracked search position to the END of each node, which broke overlapping chunks (e.g., with chunk_overlap>0). Now we track from start+1 instead of end, allowing overlaps while still fixing duplicates. Fixes test_start_end_char_idx failure.
…sitions-on-identical-text
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Bug Fix: Duplicate Node Positions for Identical Text
Problem
When parsing documents,
_postprocess_parsed_nodes()usesparent_doc.text.find()to locate each node's content in the parent document. This method always returns the first occurrence, causing nodes with identical text from different document sections to be assigned the samestart_char_idxandend_char_idx.Impact
node_info["start"]andnode_info["end"]failsExample Scenario
Document:
Chapter 1: Introduction
This is important.
Chapter 2: Methods
This is important.
Before Fix:
text="This is important.",start=24✓text="This is important.",start=24❌ (should be 63)After Fix:
text="This is important.",start=24✓text="This is important.",start=63✓Solution
Track a search cursor per document (
doc_search_positions) and search from the last found position. Since_parse_nodes()returns nodes in document order, this ensures each node is assigned to the correct sequential occurrence.Changes
llama-index-core/llama_index/core/node_parser/interface.pyllama-index-core/tests/node_parser/test_duplicate_text_positions.pyTesting
Three test cases verify:
All tests pass ✅
Files Changed
llama-index-core/llama_index/core/node_parser/interface.py- Bug fix implementationllama-index-core/tests/node_parser/test_duplicate_text_positions.py- Test suite