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From "Michael Busch (JIRA)" <>
Subject [jira] Created: (LUCENE-720) Unit tests TestBackwardsCompatibility and TestIndexFileDeleter might fail depending on JVM
Date Mon, 20 Nov 2006 23:28:02 GMT
Unit tests TestBackwardsCompatibility and TestIndexFileDeleter might fail depending on JVM

                 Key: LUCENE-720
             Project: Lucene - Java
          Issue Type: Bug
          Components: Index
    Affects Versions: 2.1
            Reporter: Michael Busch
         Assigned To: Michael McCandless
            Priority: Minor

In the two units tests TestBackwardsCompatibility and TestIndexFileDeleter several index file
names are hardcoded. For example, in TestBackwardsCompatibility.testExactFileNames() it is
tested if the index directory contains exactly the expected files after several operations
like addDocument(), deleteDocument() and setNorm() have been performed. Apparently the unit
tests pass on the nightly build machine, but in my environment (Windows XP, IBM JVM 1.5) they
fail for the following reason:

When IndexReader.setNorm() is called a new norm file for the specified field is created with
the file  ending .sx, where x is the number of the field. The problem is that the SegmentMerger
can not guarantee to keep the order of the fields, in other words after a merge took place
a field can have a different field number. This specific testcase fails, because it expects
the file ending .s0, but the file has the ending .s1.

The reason why the field numbers can be different on different JVMs is the use of HashSet
in SegmentReader.getFieldNames(). Depending on the HashSet implementation an iterator might
not iterate over the entries in insertion order. When I change HashSet to LinkedHashSet, the
two testcases pass.

However, even with a LinkedHashSet the order of the field numbers might change during a merge,
because the order in which the SegmentMerger merges the FieldInfos depends on the field options
like TERMVECTOR, INDEXED... (see SegmentMerger.mergeFields() for details). 

So I think we should not use LinkedHashSet but rather change the problematic testcases. Furthermore
I'm not sure if we should have hardcoded filenames in the tests anyway, because if we change
the index format or file names in the future these test cases would fail without modification.

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