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https://issues.apache.org/jira/browse/LUCENE-2386?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12855277#action_12855277
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Shai Erera commented on LUCENE-2386:
------------------------------------
Apparently, there are more tests that fail ... lost count but easy fixing. I
tried writing the following test:
{code}
public void testNoCommits() throws Exception {
// Tests that if we don't call commit(), the directory has 0 commits. This
has
// changed since LUCENE-2386, where before IW would always commit on a fresh
// new index.
Directory dir = new RAMDirectory();
IndexWriter writer = new IndexWriter(dir, new
IndexWriterConfig(TEST_VERSION_CURRENT, new
WhitespaceAnalyzer(TEST_VERSION_CURRENT)));
assertEquals("expected 0 commits!", 0, IndexReader.listCommits(dir).size());
// No changes still should generate a commit, because it's a new index.
writer.close();
assertEquals("expected 1 commits!", 0, IndexReader.listCommits(dir).size());
}
{code}
Simple test - validates that no commits are present following a freshly new
index creation, w/o closing or committing. However, IndexReader.listCommits
fails w/ the following exception:
{code}
java.io.FileNotFoundException: no segments* file found in
org.apache.lucene.store.ramdirect...@2d262d26: files: []
at
org.apache.lucene.index.SegmentInfos$FindSegmentsFile.run(SegmentInfos.java:652)
at
org.apache.lucene.index.SegmentInfos$FindSegmentsFile.run(SegmentInfos.java:535)
at org.apache.lucene.index.SegmentInfos.read(SegmentInfos.java:323)
at
org.apache.lucene.index.DirectoryReader.listCommits(DirectoryReader.java:1033)
at
org.apache.lucene.index.DirectoryReader.listCommits(DirectoryReader.java:1023)
at
org.apache.lucene.index.IndexReader.listCommits(IndexReader.java:1341)
at
org.apache.lucene.index.TestIndexWriter.testNoCommits(TestIndexWriter.java:4966)
....
{code}
The failure occurs when SegmentInfos attempts to find segments.gen and fails.
So I wonder if I should fix DirectoryReader to catch that exception and simply
return an empty Collection .. or I should fix SegmentInfos at this point --
notice the "files: []" at the end - I think that by adding a check to the
following code (SegmentInfos, line 652) which validates that there were any
files before throwing the exception, it'll still work properly and safely (i.e.
to detect a problematic Directory). Will need probably to break away from the
while loop and I guess fix some other things in upper layers ... therefore I'm
not sure if I should not simply catch that exception in
DirectoryReader.listCommits w/ proper documentation and be done w/ it. After
all, it's not supposed to be called ... ever? or hardly ever?
{code}
if (gen == -1) {
// Neither approach found a generation
throw new FileNotFoundException("no segments* file found in " +
directory + ": files: " + Arrays.toString(files));
}
{code}
> IndexWriter commits unnecessarily on fresh Directory
> ----------------------------------------------------
>
> Key: LUCENE-2386
> URL: https://issues.apache.org/jira/browse/LUCENE-2386
> Project: Lucene - Java
> Issue Type: Bug
> Components: Index
> Reporter: Shai Erera
> Assignee: Shai Erera
> Fix For: 3.1
>
> Attachments: LUCENE-2386.patch
>
>
> I've noticed IndexWriter's ctor commits a first commit (empty one) if a fresh
> Directory is passed, w/ OpenMode.CREATE or CREATE_OR_APPEND. This seems
> unnecessarily, and kind of brings back an autoCommit mode, in a strange way
> ... why do we need that commit? Do we really expect people to open an
> IndexReader on an empty Directory which they just passed to an IW w/
> create=true? If they want, they can simply call commit() right away on the IW
> they created.
> I ran into this when writing a test which committed N times, then compared
> the number of commits (via IndexReader.listCommits) and was surprised to see
> N+1 commits.
> Tried to change doCommit to false in IW ctor, but it got IndexFileDeleter
> jumping on me .. so the change might not be that simple. But I think it's
> manageable, so I'll try to attack it (and IFD specifically !) back :).
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