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

["Richard N. Hillegas (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DERBY-7099?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17286745#comment-17286745 ] 

Richard N. Hillegas commented on DERBY-7099:
--------------------------------------------

You appear to have a corrupted database. There are a lot of bugs associated with table compression. See https://issues.apache.org/jira/browse/DERBY-5876. Have you been compressing tables?

If you have lost confidence in the integrity of your database, you may want to dump and reload it using one of the following techniques:

* SYSCS_UTIL.SYSCS_EXPORT_TABLE commands followed by TRUNCATE TABLE commands followed by SYSCS_UTIL.SYSCS_IMPORT_TABLE commands. See the "Built-in system procedures" topic in https://db.apache.org/derby/docs/10.15/ref/index.html
* Recreating an empty schema and then populating the tables using the foreignViews optional tool described in https://db.apache.org/derby/docs/10.15/tools/index.html

> 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: 10.14.2.0, 10.15.2.0
>         Environment: Looks like environment-independent bug - reproduced in multiple environments (prod/test, win/linux, different Java and Derby versions).
>            Reporter: Ondrej Bouda
>            Priority: Critical
>         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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