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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1669) MMapDirectory on Windows silently fails to write to a file if also open for read
Date Mon, 01 Jun 2009 00:43:07 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1669?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12714947#action_12714947
] 

Michael McCandless commented on LUCENE-1669:
--------------------------------------------

That sounds exactly like what I was hitting -- getting 0 from readLong instead of the expected
56, in the above test.  Except, my test fails even before doing the hack... so it's not the
hack that's causing it.

> MMapDirectory on Windows silently fails to write to a file if also open for read
> --------------------------------------------------------------------------------
>
>                 Key: LUCENE-1669
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1669
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Store
>            Reporter: Michael McCandless
>            Priority: Minor
>
> This is not a normal situation Lucene currently encounters, though we
> are discussing exactly this possibility in LUCENE-1313.
> I only hit it in digging down on a test failure in LUCENE-1658:
> {code}
>     [junit] Testcase: testIndexAndMerge(org.apache.lucene.index.TestDoc):	FAILED
>     [junit] junit.framework.AssertionFailedError:
>     [junit] 	at org.apache.lucene.index.FieldsWriter.addRawDocuments(FieldsWriter.java:249)
>     [junit] 	at org.apache.lucene.index.SegmentMerger.mergeFields(SegmentMerger.java:350)
>     [junit] 	at org.apache.lucene.index.SegmentMerger.merge(SegmentMerger.java:139)
>     [junit] 	at org.apache.lucene.index.SegmentMerger.merge(SegmentMerger.java:116)
>     [junit] 	at org.apache.lucene.index.TestDoc.merge(TestDoc.java:182)
>     [junit] 	at org.apache.lucene.index.TestDoc.testIndexAndMerge(TestDoc.java:117)
>     [junit] 	at org.apache.lucene.util.LuceneTestCase.runTest(LuceneTestCase.java:88)
> {code}
> That failure happens on Windows 64bit, if you use MMapDirectory, and
> the index is on a remote (CIFS) mount.
> This test opens a SegmentReader against doc store files that
> IndexWriter still has open.
> I whittled it down to this test showing the root cause:
> {code}
> public void testMMapWriteRead() throws Exception {
>     MMapDirectory dir = new MMapDirectory(new File("readwrite"), null);
>     //NIOFSDirectory dir = new NIOFSDirectory(new File("readwrite"), null);
>     //SimpleFSDirectory dir = new SimpleFSDirectory(new File("readwrite"), null);
>     IndexOutput out = dir.createOutput("one");
>     out.writeLong(17);
>     out.flush();
>     // open the same file we are writing
>     dir.openInput("one").close();
>     // write another long
>     out.writeLong(56);
>     out.close();
>     IndexInput in = dir.openInput("one");
>     assertEquals(17, in.readLong());
>     assertEquals(56, in.readLong());
>     in.close();
> }
> {code}
> NIOFSDir and SimpleFSDir pass the test fine, which is nice to know
> (for LUCENE-1313).  MMapDir passes fine on a local drive, but fails on
> a remote CIFS mount.
> I'm not sure what's going on.  It seems like it could be a JRE bug --
> behavior shouldn't change on local vs remote drive.  I've only tested
> it with java 1.6.0_11.

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