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From "Tim Smith (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1703) Add a waitForMerges() method to IndexWriter
Date Mon, 22 Jun 2009 20:59:07 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1703?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12722819#action_12722819
] 

Tim Smith commented on LUCENE-1703:
-----------------------------------

I also noticed that at least on expungeDeletes() these methods may only wait for merges that
the method itself initiated

the waitForMerges() method would wait for all merges regardless of who initiated the merge.

so:
{code}
try {
  expungeDeletes(false);
} finally {
  waitForMerges();
}
{code}

would not be the same as
{code}
expungeDeletes(true);
{code}

as the later would only wait for the merges actually caused by the expungeDeletes() method

This would indicate that the waitForMerges=true/false variants of different methods should
remain

> 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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