Index: lucene/CHANGES.txt
===================================================================
--- lucene/CHANGES.txt	(revision 1508180)
+++ lucene/CHANGES.txt	(working copy)
@@ -95,6 +95,9 @@
 * LUCENE-5132: Spatial RecursivePrefixTree Contains predicate will throw an NPE
   when there's no indexed data and maybe in other circumstances too. (David Smiley)
 
+* LUCENE-5151: Associations FacetsAggregators could enter an infinite loop when
+  some result documents were missing category associations. (Shai Erera)
+
 API Changes
 
 * LUCENE-5094: Add ramBytesUsed() to MultiDocValues.OrdinalMap.
Index: lucene/facet/src/java/org/apache/lucene/facet/associations/SumFloatAssociationFacetsAggregator.java
===================================================================
--- lucene/facet/src/java/org/apache/lucene/facet/associations/SumFloatAssociationFacetsAggregator.java	(revision 1508180)
+++ lucene/facet/src/java/org/apache/lucene/facet/associations/SumFloatAssociationFacetsAggregator.java	(working copy)
@@ -54,23 +54,20 @@
     int doc = 0;
     while (doc < length && (doc = matchingDocs.bits.nextSetBit(doc)) != -1) {
       dv.get(doc, bytes);
-      if (bytes.length == 0) {
-        continue; // no associations for this document
+      if (bytes.length > 0) {
+        // aggreate float association values for ordinals
+        int bytesUpto = bytes.offset + bytes.length;
+        int pos = bytes.offset;
+        while (pos < bytesUpto) {
+          int ordinal = ((bytes.bytes[pos++] & 0xFF) << 24) | ((bytes.bytes[pos++] & 0xFF) << 16)
+              | ((bytes.bytes[pos++] & 0xFF) <<  8) | (bytes.bytes[pos++] & 0xFF);
+          
+          int value = ((bytes.bytes[pos++] & 0xFF) << 24) | ((bytes.bytes[pos++] & 0xFF) << 16)
+              | ((bytes.bytes[pos++] & 0xFF) <<  8) | (bytes.bytes[pos++] & 0xFF);
+          
+          values[ordinal] += Float.intBitsToFloat(value);
+        }
       }
-
-      // aggreate float association values for ordinals
-      int bytesUpto = bytes.offset + bytes.length;
-      int pos = bytes.offset;
-      while (pos < bytesUpto) {
-        int ordinal = ((bytes.bytes[pos++] & 0xFF) << 24) | ((bytes.bytes[pos++] & 0xFF) << 16)
-            | ((bytes.bytes[pos++] & 0xFF) <<  8) | (bytes.bytes[pos++] & 0xFF);
-        
-        int value = ((bytes.bytes[pos++] & 0xFF) << 24) | ((bytes.bytes[pos++] & 0xFF) << 16)
-            | ((bytes.bytes[pos++] & 0xFF) <<  8) | (bytes.bytes[pos++] & 0xFF);
-
-        values[ordinal] += Float.intBitsToFloat(value);
-      }
-      
       ++doc;
     }
   }
Index: lucene/facet/src/java/org/apache/lucene/facet/associations/SumIntAssociationFacetsAggregator.java
===================================================================
--- lucene/facet/src/java/org/apache/lucene/facet/associations/SumIntAssociationFacetsAggregator.java	(revision 1508180)
+++ lucene/facet/src/java/org/apache/lucene/facet/associations/SumIntAssociationFacetsAggregator.java	(working copy)
@@ -53,23 +53,20 @@
     int doc = 0;
     while (doc < length && (doc = matchingDocs.bits.nextSetBit(doc)) != -1) {
       dv.get(doc, bytes);
-      if (bytes.length == 0) {
-        continue; // no associations for this document
+      if (bytes.length > 0) {
+        // aggreate association values for ordinals
+        int bytesUpto = bytes.offset + bytes.length;
+        int pos = bytes.offset;
+        while (pos < bytesUpto) {
+          int ordinal = ((bytes.bytes[pos++] & 0xFF) << 24) | ((bytes.bytes[pos++] & 0xFF) << 16)
+              | ((bytes.bytes[pos++] & 0xFF) <<  8) | (bytes.bytes[pos++] & 0xFF);
+          
+          int value = ((bytes.bytes[pos++] & 0xFF) << 24) | ((bytes.bytes[pos++] & 0xFF) << 16)
+              | ((bytes.bytes[pos++] & 0xFF) <<  8) | (bytes.bytes[pos++] & 0xFF);
+          
+          values[ordinal] += value;
+        }
       }
-
-      // aggreate association values for ordinals
-      int bytesUpto = bytes.offset + bytes.length;
-      int pos = bytes.offset;
-      while (pos < bytesUpto) {
-        int ordinal = ((bytes.bytes[pos++] & 0xFF) << 24) | ((bytes.bytes[pos++] & 0xFF) << 16)
-            | ((bytes.bytes[pos++] & 0xFF) <<  8) | (bytes.bytes[pos++] & 0xFF);
-        
-        int value = ((bytes.bytes[pos++] & 0xFF) << 24) | ((bytes.bytes[pos++] & 0xFF) << 16)
-            | ((bytes.bytes[pos++] & 0xFF) <<  8) | (bytes.bytes[pos++] & 0xFF);
-
-        values[ordinal] += value;
-      }
-      
       ++doc;
     }
   }
Index: lucene/facet/src/test/org/apache/lucene/facet/associations/AssociationsFacetRequestTest.java
===================================================================
--- lucene/facet/src/test/org/apache/lucene/facet/associations/AssociationsFacetRequestTest.java	(revision 1508180)
+++ lucene/facet/src/test/org/apache/lucene/facet/associations/AssociationsFacetRequestTest.java	(working copy)
@@ -67,14 +67,18 @@
     AssociationsFacetFields assocFacetFields = new AssociationsFacetFields(taxoWriter);
     
     // index documents, 50% have only 'b' and all have 'a'
-    for (int i = 0; i < 100; i++) {
+    for (int i = 0; i < 110; i++) {
       Document doc = new Document();
       CategoryAssociationsContainer associations = new CategoryAssociationsContainer();
-      associations.setAssociation(aint, new CategoryIntAssociation(2));
-      associations.setAssociation(afloat, new CategoryFloatAssociation(0.5f));
-      if (i % 2 == 0) { // 50
-        associations.setAssociation(bint, new CategoryIntAssociation(3));
-        associations.setAssociation(bfloat, new CategoryFloatAssociation(0.2f));
+      // every 11th document is added empty, this used to cause the association
+      // aggregators to go into an infinite loop
+      if (i % 11 != 0) {
+        associations.setAssociation(aint, new CategoryIntAssociation(2));
+        associations.setAssociation(afloat, new CategoryFloatAssociation(0.5f));
+        if (i % 2 == 0) { // 50
+          associations.setAssociation(bint, new CategoryIntAssociation(3));
+          associations.setAssociation(bfloat, new CategoryFloatAssociation(0.2f));
+        }
       }
       assocFacetFields.addFields(doc, associations);
       writer.addDocument(doc);
@@ -185,6 +189,6 @@
     assertEquals("Wrong count for category 'b'!",10f, (float) res.get(3).getFacetResultNode().value, 0.00001);
     
     taxo.close();
-  }  
+  }
   
 }