{
  "id": 7369175,
  "title": "My coverage check did arithmetic instead of looking. All 23 pointers were wrong.",
  "url": "https://urgent.news/2026/09/14/my-coverage-check-did-arithmetic-instead-of-looking-all-23-pointers",
  "topic": "tech",
  "section": "Tech",
  "published": "2026-09-14T18:03:19.000Z",
  "source": {
    "name": "Dev.to",
    "slug": "dev-to",
    "url": "https://dev.to/mahirhir/my-coverage-check-did-arithmetic-instead-of-looking-all-23-pointers-were-wrong-502e"
  },
  "original_language": "en",
  "account": "A table in a document contains pointers to other sources. Each of the 24 rows lists a pointer indicating where the referenced information is located, enabling readers to verify the data. The coverage check for this table consistently reported success. However, the process comprised an arithmetic calculation: subtracting the number of rows with incorrect pointers from the total number of rows (24 - 23 = 1). This resulted in a false sense of completeness.\n\nThe check overlooked the actual content referenced by the pointers. Some pointers might reference non-existent lines, wrong lines, or deleted lines, yet the arithmetic still yielded zero. Once identified, all 23 pointers were found to be inaccurate, either by one or two lines. This uniform mistake across rows does not signify gradual drift but rather an inherent error from the source's creation. To resolve this issue, one must re-point the pointers and incorporate a freshness check.\n\nIn four separate instances within a week, four different readers inadvertently joined two tables incorrectly, based solely on row order. As each insertion invalidated the row order, the joins became inaccurate. Neither type of join could fail or report missing data; they could only produce incorrect results.\n\nTo address this issue, each row should now store the pointer along with a verbatim quote of the pointed content. Coverage should measure the count of rows where the quote matches the actual bytes at that location, providing a more accurate representation of the table's state. Retired rows should be excluded from the denominator, and the check should no longer merely count rows but assess the real-world state of the data. This approach enables a more effective diagnosis of errors and ensures the correctness of the reported coverage.",
  "summary": "A table in one document points into another. Each of its 24 rows carries a source pointer saying where the thing it describes actually lives, so a reader can go and check. The coverage check for that table reported complete, always. Here is what it did: rows in the table 24 rows carrying a pointer 23 rows that are a vessel 1 24 - 23 - 1 = 0 uncovered -> complete That is arithmetic over counts. It…",
  "key_points": [
    "Coverage check reported success despite arithmetic error",
    "23 pointers found inaccurate, not 1 as calculated",
    "Solution involves storing quotes with pointers and freshness check"
  ],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}