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https://issues.apache.org/jira/browse/LUCENE-743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12538743
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Michael McCandless commented on LUCENE-743:
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OK I think this patch is very close! I finished reviewing it --
here's some more feedback:
- In multiple places you catch an IOException and undo the attempted
re-open, but shouldn't this be a try/finally instead so you also
clean up on hitting any unchecked exceptions?
- I think you need an explicit refCount for the Norm class in
SegmentReader.
.
Say I've done a chain of 10 re-opens for SegmentReader and each
time only the segment's norms has changed. I've closed all but
the last SegmentReader. At this point all 10 SegmentReaders are
still alive (RC > 0) and holding open all file handles for their
copies of the norms. So this will leak file handles/RAM with each
reopen?
.
To fix this, I think you just need to add refCount into Norm class
& set refCount to 1 in the constructor. Then, each each
SegmentReader calls Norm.decRef(), not Norm.close(), when it's
done. When refCount hits 0 then the Norm closes itself. Finally,
during re-open you should share a Norm instance (rather than open
a new one) if it had not changed from the previous SegmentReader.
.
For singleNormStream, I think each reopened SegmentReader should
always re-open this descriptor and then we can forcefully close
this stream when the SegmentReader is closed (what you are doing
now). Ie the SegmentReader fully owns singleNormStream.
- If you have a long series of reopens, then, all SegmentReaders in
the chain will remain alive. So this is a [small] memory leak
with time. I think if you changed referencedSegmentReader to
always be the *starting* SegmentReader then this chain is broken
and after 10 reopens only the original SegmentReader and the most
recent one will remain alive (assuming I closed all SegmentReaders
but the most recent one).
> IndexReader.reopen()
> --------------------
>
> Key: LUCENE-743
> URL: https://issues.apache.org/jira/browse/LUCENE-743
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Index
> Reporter: Otis Gospodnetic
> Assignee: Michael Busch
> Priority: Minor
> Fix For: 2.3
>
> Attachments: IndexReaderUtils.java, lucene-743-take2.patch,
> lucene-743-take3.patch, lucene-743.patch, lucene-743.patch, lucene-743.patch,
> MyMultiReader.java, MySegmentReader.java,
> varient-no-isCloneSupported.BROKEN.patch
>
>
> This is Robert Engels' implementation of IndexReader.reopen() functionality,
> as a set of 3 new classes (this was easier for him to implement, but should
> probably be folded into the core, if this looks good).
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