DO NOT REPLY [Bug 30330] New: - IndexReader.delete(term) does not delete last doc from TermDocs list

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http://issues.apache.org/bugzilla/show_bug.cgi?id=30330

IndexReader.delete(term) does not delete last doc from TermDocs list

           Summary: IndexReader.delete(term) does not delete last doc from
                    TermDocs list
           Product: Lucene
           Version: 1.4
          Platform: Other
        OS/Version: Other
            Status: NEW
          Severity: Normal
          Priority: Other
         Component: Index
        AssignedTo: lucene-dev@jakarta.apache.org
        ReportedBy: alan@collison.net


It appears that delete(term) fails to delete the last document containing term, which
for a unique match means that you can't remove an individual document.

Code attempting to remove document with specific 'path' (slightly modified version of demo code):

Directory directory = FSDirectory.getDirectory("index", false);
IndexReader reader = IndexReader.open(directory);
Term term = new Term("path", args[0]);  // path passed via command line arg
int deleted = reader.delete(term);
reader.close();
directory.close();

System.out.println("deleted " + deleted + " documents containing " + term);

Executing this always returns "deleted 0 documents containing <path entered>"

In IndexReader.java, delete() has:

public final int delete(Term term) throws IOException {
  TermDocs docs = termDocs(term);
  if (docs == null) return 0;
  int n = 0;
  try {
    while (docs.next()) {
      delete(docs.doc());
      n++;
    }
  } finally {
    docs.close();
  }
  return n;
}

It appears that docs.next() always returns false when there is only one doc, hence
delete() is never called and 0 is always returned.  I assume that this also means that
if there are multiple matches, the last doc will not be deleted either, but I have not tested
that.

I modified the code as follows:

    boolean more = true;
    try {
      docs.next();
      while (more) {
        delete(docs.doc());
        n++;
        more = docs.next();
      }
    } finally {
      docs.close();
    }

and then it worked as expected (at least attempts to delete a single document from the
index succeeded whereas previously they did not).

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