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  1. Derby
  2. DERBY-7099

DELETE skips a row matching the WHERE clause (single delete by PK)

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    • Bug
    • Status: Open
    • Critical
    • Resolution: Unresolved
    • None
    • SQL
    • None
    • Looks like environment-independent bug - reproduced in multiple environments (prod/test, win/linux, different Java and Derby versions).
    • Normal
    • Repro attached
    • Data corruption, Seen in production


      We came across a bug in Derby when a DELETE by primary key actually does not delete the row (although it exists).

      • We found the issue in a delete-reinsert use case when the reinsert was failing with a "duplicate key" error.
      • Note: The attached app to reproduce the issue follows this reinsert pattern.

      To reproduce the issue, a SELECT (by PK) is required before the DELETE (by PK).

      • SELECT => SELECT => DELETE => RE-INSERT => duplicate key error.
      • The DELETE works OK if no or just 1 SELECT is executed before.
      • The "failed" DELETE correctly reports "0 rows affected".
      • Retrying the DELETE makes the delete really happen.
      • The behavior is the same both for autocommit and manual commit mode.
      • The behavior is 100% reproducible in the attached demo app.
        However, it is not reproducible from DBeaver (using the same queries).

      Notes regarding the attached database + demo app to reproduce the issue:

      • The app takes 3 arguments: path to the database (string), how many times to execute the initial SELECT (int) and an optional "retry" string to retry the DELETE statement.
      • Use "test_app.bat" => there are several execution scenarios, uncomment the one you intend to test.
      • With 0-1 SELECTs, the demo app works without any issues.
      • With 2+ SELECTs, the demo app fails on "duplicate key" when trying to reinsert the deleted row. The app reports that the DELETE affected 0 rows.
      • In the "retry" mode, you can see that 2nd DELETE is successful (even for 3+ SELECTs).

      Further notes

      • The issue persists even after a successful delete-reinsert.
      • Check for corruption (SYSCS_CHECK_TABLE) indicates that the table is healthy.
      • Full rebuild of the affected table (SYSCS_COMPRESS_TABLE) resolves the issue but - there is no way to tell whether a tables needs rebuild to avoid this kind of issue...


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            Unassigned Unassigned
            obouda@gk-software.com Ondrej Bouda




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