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From "Shai Erera (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1703) Add a waitForMerges() method to IndexWriter
Date Sat, 20 Jun 2009 17:58:07 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1703?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12722231#action_12722231
] 

Shai Erera commented on LUCENE-1703:
------------------------------------

bq. Though we have a migration challenge (if we want to swap the default). Or we add a matchVersion.

If we change the default to not wait, then I don't think matchVersion will matter. Since I'll
need to update my code anyway, I don't think I'd care whether I call waitForMerges(), or matchVersion,
even though the latter is called only once and the change is required in just one place. matchVersion,
IMO, is required in more complicated cases, like that ACRONYM issue, which my code really
has no control over.

> Add a waitForMerges() method to IndexWriter
> -------------------------------------------
>
>                 Key: LUCENE-1703
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1703
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>    Affects Versions: 2.4
>            Reporter: Tim Smith
>         Attachments: IndexWriter.java.diff, IndexWriter.java.diff
>
>
> It would be very useful to have a waitForMerges() method on the IndexWriter.
> Right now, the only way i can see to achieve this is to call IndexWriter.close()
> ideally, there would be a method on the IndexWriter to wait for merges without actually
closing the index.
> This would make it so that background merges (or optimize) can be waited for without
closing the IndexWriter, and then reopening a new IndexWriter
> the close() reopen IndexWriter method can be problematic if the close() fails as the
write lock won't be released
> this could then result in the following sequence:
> * close() - fails
> * force unlock the write lock (per close() documentation)
> * new IndexWriter() (acquires write lock)
> * finalize() on old IndexWriter releases the write lock
> * Index is now not locked, and another IndexWriter pointing to the same directory could
be opened
> If you don't force unlock the write lock, opening a new IndexWriter will fail until garbage
collection calls finalize() the old IndexWriter
> If the waitForMerges() method is available, i would likely never need to close() the
IndexWriter until right before the process being shutdown, so this issue would not occur (worst
case scenario, the waitForMerges() fails)

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