db-derby-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4849) Re-compilation may cause duplicate entries in the XPLAIN table
Date Tue, 02 Nov 2010 09:12:29 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12927335#action_12927335
] 

Knut Anders Hatlen commented on DERBY-4849:
-------------------------------------------

As to the NO_WAIT+retry option, if I've understood correctly, I don't think that alone would
solve the deadlock issue. The transaction will still hold the locks that it has already acquired,
and the other thread(s) involved in the deadlock will still be blocked, so the retry will
just run into the same deadlock again. It may work if the transaction releases the locks before
retrying, but I think syscs_update_statistics does all its work in the user transaction, and
we need to use nested transactions if we want to release exclusive locks in the middle of
a user transaction. We'd also need to decide how many times we should retry before giving
up, and perhaps also how long to wait between each retry.

> Re-compilation may cause duplicate entries in the XPLAIN table
> --------------------------------------------------------------
>
>                 Key: DERBY-4849
>                 URL: https://issues.apache.org/jira/browse/DERBY-4849
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.6.2.1, 10.7.1.0
>            Reporter: Kristian Waagan
>            Assignee: Kristian Waagan
>            Priority: Minor
>         Attachments: derby-4849-1a-narrow_fix.diff, derby-4849-2a-broad_fix.diff, derby-4849-2b-broad_fix_with_test.diff,
derby-4849-2b-broad_fix_with_test.stat, derby-4849-2c-broad_fix_with_test.diff, derby-4849-xplain_duplicate_stacktrace.txt
>
>
> If happening at the right moment, a re-compilation request may cause duplicate entries
in the XPLAIN statement tables.
> I have only confirmed this for the SYSXPLAIN_STATEMENTS table, and I do not know if the
other XPLAIN tables are affected.
> The error is highly intermittent, and so far I have only been able to trigger it when
testing the automatic index statistics update prototype.
> See the attached stack-trace for some more details.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message