[jira] [Created] (DERBY-7099) DELETE skips a row matching the WHERE clause (single delete by PK)

["Ondrej Bouda (Jira)" <ji...@apache.org>]

Ondrej Bouda created DERBY-7099:
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             Summary: DELETE skips a row matching the WHERE clause (single delete by PK)
                 Key: DERBY-7099
                 URL: https://issues.apache.org/jira/browse/DERBY-7099
             Project: Derby
          Issue Type: Bug
          Components: SQL
    Affects Versions: 10.15.2.0, 10.14.2.0
         Environment: Looks like environment-independent bug - reproduced in multiple environments (prod/test, win/linux, different Java and Derby versions).
            Reporter: Ondrej Bouda
         Attachments: repro.zip

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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