diff --git a/hyracks-fullstack/hyracks/hyracks-util/pom.xml b/hyracks-fullstack/hyracks/hyracks-util/pom.xml
index b69d509..4993443 100644
--- a/hyracks-fullstack/hyracks/hyracks-util/pom.xml
+++ b/hyracks-fullstack/hyracks/hyracks-util/pom.xml
@@ -99,6 +99,10 @@
       <groupId>com.google.guava</groupId>
       <artifactId>guava</artifactId>
     </dependency>
+    <dependency>
+      <groupId>it.unimi.dsi</groupId>
+      <artifactId>fastutil</artifactId>
+    </dependency>
   </dependencies>
 
 </project>
diff --git a/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/fastutil/Collectors.java b/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/fastutil/Collectors.java
new file mode 100644
index 0000000..b15154b
--- /dev/null
+++ b/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/fastutil/Collectors.java
@@ -0,0 +1,131 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.hyracks.util.fastutil;
+
+import java.util.Collections;
+import java.util.Objects;
+import java.util.Set;
+import java.util.function.BiConsumer;
+import java.util.function.BinaryOperator;
+import java.util.function.Function;
+import java.util.function.Supplier;
+import java.util.stream.Collector;
+import java.util.stream.Collector.Characteristics;
+
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
+import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
+
+public class Collectors {
+
+    private static final Set<Characteristics> IDENTITY_CHARACTERISTICS =
+            Collections.singleton(Characteristics.IDENTITY_FINISH);
+
+    private Collectors() {
+        throw new AssertionError("do not instantiate");
+    }
+
+    public static <T> Collector<Int2ObjectMap.Entry<T>, Int2ObjectMap<T>, Int2ObjectMap<T>> toInt2ObjectMap() {
+        return new Collector<Int2ObjectMap.Entry<T>, Int2ObjectMap<T>, Int2ObjectMap<T>>() {
+            @Override
+            public Supplier<Int2ObjectMap<T>> supplier() {
+                return Int2ObjectOpenHashMap::new;
+            }
+
+            @Override
+            public BiConsumer<Int2ObjectMap<T>, Int2ObjectMap.Entry<T>> accumulator() {
+                return (map, element) -> {
+                    int key = element.getIntKey();
+                    T value = Objects.requireNonNull(element.getValue());
+                    T oldValue = map.putIfAbsent(key, value);
+                    if (oldValue != null)
+                        throw duplicateKey(key, oldValue, value);
+                };
+            }
+
+            @Override
+            public BinaryOperator<Int2ObjectMap<T>> combiner() {
+                return (map1, map2) -> {
+                    for (Int2ObjectMap.Entry<T> e : map2.int2ObjectEntrySet()) {
+                        accumulator().accept(map1, e);
+                    }
+                    return map1;
+                };
+            }
+
+            @Override
+            public Function<Int2ObjectMap<T>, Int2ObjectMap<T>> finisher() {
+                return Function.identity();
+            }
+
+            @Override
+            public Set<Characteristics> characteristics() {
+                return IDENTITY_CHARACTERISTICS;
+            }
+
+        };
+    }
+
+    public static <T> Collector<Long2ObjectMap.Entry<T>, Long2ObjectMap<T>, Long2ObjectMap<T>> toLong2ObjectMap() {
+        return new Collector<Long2ObjectMap.Entry<T>, Long2ObjectMap<T>, Long2ObjectMap<T>>() {
+            @Override
+            public Supplier<Long2ObjectMap<T>> supplier() {
+                return Long2ObjectOpenHashMap::new;
+            }
+
+            @Override
+            public BiConsumer<Long2ObjectMap<T>, Long2ObjectMap.Entry<T>> accumulator() {
+                return (map, element) -> {
+                    long key = element.getLongKey();
+                    T value = Objects.requireNonNull(element.getValue());
+                    T oldValue = map.putIfAbsent(key, value);
+                    if (oldValue != null)
+                        throw duplicateKey(key, oldValue, value);
+                };
+            }
+
+            @Override
+            public BinaryOperator<Long2ObjectMap<T>> combiner() {
+                return (map1, map2) -> {
+                    for (Long2ObjectMap.Entry<T> e : map2.long2ObjectEntrySet()) {
+                        accumulator().accept(map1, e);
+                    }
+                    return map1;
+                };
+            }
+
+            @Override
+            public Function<Long2ObjectMap<T>, Long2ObjectMap<T>> finisher() {
+                return Function.identity();
+            }
+
+            @Override
+            public Set<Characteristics> characteristics() {
+                return IDENTITY_CHARACTERISTICS;
+            }
+
+        };
+    }
+
+    private static IllegalStateException duplicateKey(Object key, Object oldValue, Object newValue) {
+        return new IllegalStateException("Duplicate key " + key + " (old: " + oldValue + ", new: " + newValue + ")");
+    }
+
+}