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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4771) Continue investigation of automatic creation/update of index statistics
Date Thu, 25 Nov 2010 22:12:13 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12935889#action_12935889

Dag H. Wanvik commented on DERBY-4771:

Some comments on the tests first (started with those). Looks good, as
far as I can understand the tests do test the auto-update feature in
many aspects, and the MT test stresses it with concurrent drop/create
of the table in question. Without the rest of the patch, the
AutomaticIndexStatisticsTest fail as expected;
AutomaticIndexStatisticsTest also hung waiting for three stat entries,
that's ok I guess.

AutomaticIndexStatisticsMultiTest worked also without the rest of the
patch, but it still adds value since we know auto-update happens now,
so the code paths exercised is different.

Some comments on AutomaticIndexStatisticsTest:

  * hard-coded use of "system" & "system/wombat" should be avoided
  * Is 500ms wait for daemon to update stats enough/stable
    enough for the tests? Have you measured how long it
    typically takes?
  * Does testStatsCreatedOnGrowth add any value compared to
  * hardwired constant string "masterDb"
  * Not safe to copy db without freezing source db?
    (post-commit could do writes?)
  * I guess testDropWhileScanningThenDelete doesn't really know
    for sure whether it exercised to logic to stop scan (based
    on timing), so just passing isn't proof the right thing
    happened. Probably hard to improve on that though? Maybe you
    could start with one statistics and assert that its still
    same date after shutting down & rebooting?
  * // We expect three stats objects: base table, index and
    third is ? Would be nice with explanation in comment here.
  * dumpLocks isn't used, so could be commented out or removed.

More when I have looked into the implementation.

> Continue investigation of automatic creation/update of index statistics
> -----------------------------------------------------------------------
>                 Key: DERBY-4771
>                 URL: https://issues.apache.org/jira/browse/DERBY-4771
>             Project: Derby
>          Issue Type: Task
>          Components: SQL, Store
>    Affects Versions:
>            Reporter: Kristian Waagan
>            Assignee: Kristian Waagan
>         Attachments: autoindexstats.html, derby-4771-1a-prototype_code_dump.diff, derby-4771-1a-prototype_code_dump.stat,
derby-4771-1b-prototype_code_dump.diff, derby-4771-2a-prototype_lcc_code_dump.diff, derby-4771-2b-prototype_lcc_code_dump.diff,
derby-4771-2c-prototype_lcc_code_dump.diff, derby-4771-2d-prototype_lcc_code_dump.diff, derby-4771-2e-prototype_lcc_code_dump.diff,
derby.log, error-stacktrace.out, rjall.out, rjall.out, rjall.out, rjall.rar, rjone.out
> Work was started to improve Derby's handling of index statistics. This issue tracks further
discussion and work for this task.

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