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## Summary
PDF files often contain a bookmark/outline tree (table of contents built
into the file by the authoring tool). RAGFlow's `pdf_parser.outlines`
already extracts these `(title, depth)` tuples via pypdf, but they are
used ephemerally during chunking (`manual` parser uses them for
hierarchy detection) and then discarded.
This PR persists the outline as `doc.meta_fields["outline"]` — a JSON
array of `{"title": str, "depth": int}` objects — so downstream features
can use the structural information.
### Why this matters
- **Complementary to `toc_extraction`** — the existing `toc_extraction`
feature uses LLM calls to generate a TOC and only works for the `naive`
parser. The raw PDF outline is free (already extracted by pypdf), works
for all parsers, and captures the author's original document structure.
- **Document navigation** — frontends can render a clickable TOC from
the outline
- **Entity extraction** — the outline provides a structural map for
identifying document sections and key topics
- **Search result context** — knowing which section a chunk belongs to
helps users evaluate relevance
### Changes
| File | Change | LOC |
|------|--------|-----|
| `rag/app/naive.py` | Attach `pdf_parser.outlines` as `__outline__` on
first chunk dict | ~7 |
| `rag/app/manual.py` | Same for the manual parser | ~5 |
| `rag/svr/task_executor.py` | Extract `__outline__`, persist via
`DocMetadataService.update_document_metadata()` | ~12 |
### Design decisions
- **Transient key pattern**: The outline is passed from parser →
task_executor via `__outline__` on the first chunk dict, then removed
before indexing. This follows the same pattern as `metadata_obj` for
LLM-generated metadata.
- **No schema changes**: Uses the existing `meta_fields` JSON column on
the document table.
- **Graceful degradation**: If a PDF has no outline (common for scanned
docs), nothing is stored. If persistence fails, it logs a warning and
continues — parsing is not interrupted.
### Backward compatibility
- **Fully backward compatible** — no existing fields, behavior, or
schemas changed
- PDFs without outlines are unaffected
- Existing `meta_fields` data is preserved (merged, not overwritten)
## Test plan
- [ ] Parse a PDF with bookmarks (e.g. any multi-chapter document),
verify `meta_fields["outline"]` is populated
- [ ] Parse a PDF without bookmarks, verify no errors and no outline key
in meta_fields
- [ ] Verify existing `meta_fields` data is preserved (not overwritten)
when outline is added
- [ ] Verify `manual` parser also persists outlines
- [ ] Verify outline JSON structure: `[{"title": "Chapter 1", "depth":
0}, ...]`
Related: #9921 (Deterministic Document Access Layer)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: yuch85 <yuch85.1@gmail.com>
Co-authored-by: Wang Qi <wangq8@outlook.com>