Document Drafting and Material Preparation for Rail Transit Equipment: Document Parsing and Chunking

What the data for this category looks like

Rail transit equipment document data mainly comes from three sources: enterprise PLM systems, production workshop process documents, and quality inspection acceptance reports. Updates follow production batches and technical renovation projects, with completion within 1 to 3 days after new vehicle model launch or process adjustment. Documents include fixed fields: vehicle model number, component model number, material grade, torque value, dimensional tolerance. Units are mostly N·m and mm. There are single-page spare parts list Excel files, as well as dozens of pages of full vehicle assembly process PDFs. Some documents contain nested tables and technical parameter diagrams.

What constraints these characteristics impose on the document parsing and chunking step

The presence of fixed fields and specialized units requires precise identification of the binding relationship between parameters and units during parsing, to avoid separating parameters from their units after chunking. The existence of nested tables and technical diagrams will cause general parsing tools to lose inline associated table data and miss dimensional parameters from diagram annotations. The characteristic of long documents being updated by production batch requires the chunking logic to adapt to the document's chapter structure. Hard splitting by fixed character count will damage the integrity of process steps. Excel-format spare parts lists contain large volumes of structured data, and it is necessary to avoid splitting spare part information across rows, which would prevent matching complete component parameters during subsequent retrieval.

How to Set Configurations

Reference only; verify against the target FastGPT release and deployment documentation.

| chunkSplitter | Split by chapter and fixed fields | Documents have fixed chapter structures and anchor fields such as vehicle model and component numbers. Splitting by chapter avoids parameter confusion from cross-chapter splicing, and meets the retrieval needs of structured documents |

| customPdfParse | Enabled | Native parsing cannot fully extract nested tables and diagram annotation parameters. Custom parsing adapts to structured tables and technical diagrams within rail transit equipment documents |

| UPLOAD_FILE_MAX_SIZE | 500 MB | The total size of a single full vehicle assembly process PDF or multi-batch spare parts list Excel files usually does not exceed this value, preventing abnormal interruptions during upload |

| PARSE_FILE_TIMEOUT_SECONDS | 300 seconds | Large long documents require longer processing time. This duration covers the parsing process for most documents, and can be adjusted based on document scale as calibrated by actual testing |

| chunkSettingMode | Manual configuration | It is necessary to adjust chunking rules for different types of rail transit equipment documents such as process manuals and spare parts lists. Manual configuration adapts to scenario differences |

Three Common Misconfigurations

• Nested table cell content is missing in the parsing result after uploading a PDF document. The customPdfParse configuration is not enabled, and native parsing cannot recognize the nested technical table structure in rail transit equipment documents.
• After uploading an Excel-format spare parts list, only the header row is extracted with no specific component data. The chunkSplitter rule is not adjusted, and the default chunking logic skips data rows when splitting by row, or no parsing adaptation for Excel structured data is configured.
• Torque values and their units N·m are separated in the post-parsing chunked content, such as only retaining "120" while losing "N·m". The chunkSize setting is too small, splitting parameters and their bound units into different chunks, or the binding recognition logic for parameters and units is not enabled.

How to Confirm Configurations Are Correct

• Upload a typical rail transit equipment process PDF document, check if all cell content of nested tables is fully retained in the parsing result, to confirm that the customPdfParse configuration is active.
• Upload a spare parts list Excel file, verify that the extracted component data includes complete model, material, and quantity fields, to confirm that the Excel structured data parsing adaptation configuration is correct.
• Randomly select a segment of a long document, check if the chunked content retains complete process steps or parameter groups, to confirm that the chunkSize and chunkSplitter configurations match the document structure characteristics.
• Set PARSE_FILE_TIMEOUT_SECONDS to 300 seconds, upload a large document within 500 MB, to confirm that the parsing process does not trigger a timeout error.

The values provided here are common starting points, and should be evaluated against the reader's own samples.

Question material comes from public community discussions. Configuration values are common starting points and should be measured against your own samples. Verified on 2026-09-28.