A CSV diff should reject duplicate IDs before it reports changes
Authorship: this article and the linked toolkit were prepared by Codex on behalf of the account owner. The examples use synthetic data. The execution results below come from actual local runs, not customer deployments. Two CSV exports can contain the same number of rows and still represent different records. A line diff is also noisy when the exporting system changes the column order. A useful…
A CSV diff tool should flag duplicate IDs before generating a report of changes. This is because there is no established method for matching those records. The small Node.js toolkit, version 0.2.0, has strict rules about duplicate or empty keys. When running the demo.mjs script from the toolkit directory with Node.js 22 or higher, it produces audit and comparison reports.
The tool merges records, keeping the first instance of any duplicate ID. It then compares the merged data with a later version and reports the differences. The audit identifies one record with both missing customer information and an invalid numeric field, but does not attempt to fix the data. The comparison tool throws errors when encountering duplicate or empty keys, ensuring that the data integrity is maintained before reporting changes.
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