## What problem does this PR solve?
Closes#15874
Both the `POST /api/v1/datasets/<dataset_id>/chunks` (re-parse) and
`DELETE /api/v1/datasets/<dataset_id>/chunks` (stop-parsing) handlers
called `settings.docStoreConn.delete` unconditionally. When the
tenant/dataset index has not been created yet — fresh dataset, first
parse interrupted before any chunks were indexed, or index manually
removed — the delete call throws and the handler returns HTTP 500
**after** the document state was already mutated (RUNNING with zeroed
counters for the parse path; CANCEL with zeroed counters for the stop
path), leaving the document in an inconsistent state.
The newer `parse_documents` path in `document_api.py` already uses
`index_exist` before deleting:
## How to fix?
Apply the same `index_exist` guard to both call sites in `chunk_api.py`:
- **`parse`** (POST path, line ~192): guard the delete before
`TaskService.filter_delete`.
- **`stop_parsing`** (DELETE path, line ~242): guard the delete after
`DocumentService.update_by_id`.
Both sites already have the correct `search.index_name(tenant_id)` and
`dataset_id` parameters; the guard is a one-line addition at each site.
## Type of change
- [x] Bug fix (non-breaking change which fixes an issue)
---------
Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: Wang Qi <wangq8@outlook.com>
### What problem does this PR solve?
Python implementation of the Go-based model_provider API suite.
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
---------
Co-authored-by: bill <yibie_jingnian@163.com>
### What problem does this PR solve?
Refactor: speed up ragflow server, save startup memory, saved 200MiB,
and 5-9 seconds start time.
##### Before
1241292 | | \_ python3 api/ragflow_server.py
RAGFlow server is ready after 25.61845850944519s initialization.
##### After
1019968 | | \_ python3 api/ragflow_server.py
RAGFlow server is ready after 16.205134391784668s initialization.
### Type of change
- [x] Refactoring
