Index: lucene/CHANGES.txt
===================================================================
--- lucene/CHANGES.txt	(revision 1133885)
+++ lucene/CHANGES.txt	(working copy)
@@ -468,6 +468,11 @@
 * LUCENE-3102: CachingCollector.replay was failing to call setScorer
   per-segment (Martijn van Groningen via Mike McCandless)
 
+* LUCENE-3183: Fix rare corner case where seeking to empty term
+  (field="", term="") with terms index interval 1 could hit
+  ArrayIndexOutOfBoundsException (selckin, Robert Muir, Mike
+  McCandless)
+
 New Features
 
 * LUCENE-3140: Added experimental FST implementation to Lucene.
Index: lucene/src/test/org/apache/lucene/index/TestIndexWriter.java
===================================================================
--- lucene/src/test/org/apache/lucene/index/TestIndexWriter.java	(revision 1133885)
+++ lucene/src/test/org/apache/lucene/index/TestIndexWriter.java	(working copy)
@@ -73,6 +73,7 @@
 import org.apache.lucene.util.ThreadInterruptedException;
 import org.apache.lucene.util.UnicodeUtil;
 import org.apache.lucene.util._TestUtil;
+import org.apache.lucene.index.codecs.preflexrw.PreFlexRWCodec;
 
 public class TestIndexWriter extends LuceneTestCase {
 
@@ -1763,4 +1764,19 @@
     reader.close();
     dir.close();
   }
+
+  // LUCENE-3183
+  public void testEmptyFieldNameTIIOne() throws IOException {
+    Directory dir = newDirectory();
+    IndexWriterConfig iwc = newIndexWriterConfig(TEST_VERSION_CURRENT, new MockAnalyzer(random))
+      .setCodecProvider(_TestUtil.alwaysCodec(new PreFlexRWCodec()));
+    iwc.setTermIndexInterval(1);
+    iwc.setReaderTermsIndexDivisor(1);
+    IndexWriter writer = new IndexWriter(dir, iwc);
+    Document doc = new Document();
+    doc.add(newField("", "a b c", Field.Store.NO, Field.Index.ANALYZED));
+    writer.addDocument(doc);
+    writer.close();
+    dir.close();
+  }
 }
Index: lucene/src/java/org/apache/lucene/index/codecs/preflex/SegmentTermEnum.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/codecs/preflex/SegmentTermEnum.java	(revision 1133885)
+++ lucene/src/java/org/apache/lucene/index/codecs/preflex/SegmentTermEnum.java	(working copy)
@@ -153,8 +153,12 @@
     return true;
   }
 
-  /** Optimized scan, without allocating new terms. 
-   *  Return number of invocations to next(). */
+  /* Optimized scan, without allocating new terms. 
+   *  Return number of invocations to next().
+   *
+   * NOTE: LUCENE-3183: if you pass Term("", "") here then this
+   * will incorrectly return before positioning the enum,
+   * and position will be -1; caller must detect this. */
   final int scanTo(Term term) throws IOException {
     scanBuffer.set(term);
     int count = 0;
Index: lucene/src/java/org/apache/lucene/index/codecs/preflex/TermInfosReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/codecs/preflex/TermInfosReader.java	(revision 1133885)
+++ lucene/src/java/org/apache/lucene/index/codecs/preflex/TermInfosReader.java	(working copy)
@@ -57,6 +57,7 @@
     final long termOrd;
     public TermInfoAndOrd(TermInfo ti, long termOrd) {
       super(ti);
+      assert termOrd >= 0;
       this.termOrd = termOrd;
     }
   }
@@ -306,7 +307,13 @@
       ti = enumerator.termInfo;
       if (tiOrd == null) {
         if (useCache) {
-          termsCache.put(new CloneableTerm(term), new TermInfoAndOrd(ti, enumerator.position));
+          // LUCENE-3183: it's possible, if term is Term("",
+          // ""), for the STE to be incorrectly un-positioned
+          // after scan-to; work around this by not caching in
+          // this case:
+          if (enumerator.position >= 0) {
+            termsCache.put(new CloneableTerm(term), new TermInfoAndOrd(ti, enumerator.position));
+          }
         }
       } else {
         assert sameTermInfo(ti, tiOrd, enumerator);