diff --git a/asterix-app/src/test/resources/runtimets/queries/custord/order_q_04.aql b/asterix-app/src/test/resources/runtimets/queries/custord/order_q_04.aql
index b2d55d9..e2fd5b6 100644
--- a/asterix-app/src/test/resources/runtimets/queries/custord/order_q_04.aql
+++ b/asterix-app/src/test/resources/runtimets/queries/custord/order_q_04.aql
@@ -26,4 +26,4 @@
 let $c2 := {{ $o.orderstatus, $o.clerk}}
 let $c3 := [$o.heList, $o.openlist, $o.loc, $o.line, $o.poly, $o.lastorder]
 let $c4 := [$o.heList, $o.openlist, $o.loc, $o.line, $o.poly, $o.lastorder]
-return { "orderid": $o.oid, "ordertot":$o.total, "list": $c3, "item1": $c3[0], "item1": $c3[?], "item2": $c3[1], "item5": $c3[5], "item10": $c3[10]}
+return { "orderid": $o.oid, "ordertot":$o.total, "list": $c3, "item1": $c3[0], "item2": $c3[1], "item5": $c3[5], "item10": $c3[10]}
diff --git a/asterix-app/src/test/resources/runtimets/queries/custord/order_q_05.aql b/asterix-app/src/test/resources/runtimets/queries/custord/order_q_05.aql
index 5693312..481c1fd 100644
--- a/asterix-app/src/test/resources/runtimets/queries/custord/order_q_05.aql
+++ b/asterix-app/src/test/resources/runtimets/queries/custord/order_q_05.aql
@@ -24,4 +24,4 @@
 for $o in dataset('Orders')
 let $c1 := []
 let $c2 := {{}}
-return { "orderid": $o.oid, "ordertot":$o.total, "emptyorderedlist": $c1, "emptyunorderedlist": $c2, "olist_item1": $c1[0], "olist_item1": $c1[?], "olist_item5": $c1[4], "ulist_item1": $c2[?]}
+return { "orderid": $o.oid, "ordertot":$o.total, "emptyorderedlist": $c1, "emptyunorderedlist": $c2, "olist_item1": $c1[0], "olist_item5": $c1[4], "ulist_item1": $c2[?]}
diff --git a/asterix-app/src/test/resources/runtimets/results/custord/order_q_04.adm b/asterix-app/src/test/resources/runtimets/results/custord/order_q_04.adm
index f22ea7f..3992f7d 100644
--- a/asterix-app/src/test/resources/runtimets/results/custord/order_q_04.adm
+++ b/asterix-app/src/test/resources/runtimets/results/custord/order_q_04.adm
@@ -1,4 +1,4 @@
-{ "orderid": 1000, "ordertot": 97.20656f, "list": [ [ "1.0f", "yassser" ], [ 11, 14, "yasir", 1.6f ], point("10.1,11.1"), line("10.1,11.1 10.2,11.2"), polygon("1.2,1.3 2.1,2.5 3.5,3.6 4.6,4.8"), null ], "item1": [ "1.0f", "yassser" ], "item1": [ "1.0f", "yassser" ], "item2": [ 11, 14, "yasir", 1.6f ], "item5": null, "item10": null }
-{ "orderid": 10, "ordertot": 7.206f, "list": [ [ 1.0f, "5.2f", "60" ], [ 13231, "foo", null, 13.25d, 13.2f ], point("10.1,11.1"), line("10.1,11.1 10.2,11.2"), polygon("1.2,1.3 2.1,2.5 3.5,3.6 4.6,4.8"), null ], "item1": [ 1.0f, "5.2f", "60" ], "item1": [ 1.0f, "5.2f", "60" ], "item2": [ 13231, "foo", null, 13.25d, 13.2f ], "item5": null, "item10": null }
-{ "orderid": 100, "ordertot": 124.26f, "list": [ [ 1.3f, 5.2f, "60", 12.32f ], [ 10, 2.0f, 3.0d, 40 ], point("10.1,11.1"), line("10.1,11.1 10.2,11.2"), polygon("1.2,1.3 2.1,2.5 3.5,3.6 4.6,4.8"), null ], "item1": [ 1.3f, 5.2f, "60", 12.32f ], "item1": [ 1.3f, 5.2f, "60", 12.32f ], "item2": [ 10, 2.0f, 3.0d, 40 ], "item5": null, "item10": null }
-{ "orderid": 10, "ordertot": 14.2326f, "list": [ [ 2.4f, "15" ], [ 110 ], point("10.1,11.1"), line("10.1,11.1 10.2,11.2"), polygon("1.2,1.3 2.1,2.5 3.5,3.6 4.6,4.8"), { "oid": 75, "total": 87.61863f } ], "item1": [ 2.4f, "15" ], "item1": [ 2.4f, "15" ], "item2": [ 110 ], "item5": { "oid": 75, "total": 87.61863f }, "item10": null }
+{ "orderid": 1000, "ordertot": 97.20656f, "list": [ [ "1.0f", "yassser" ], [ 11, 14, "yasir", 1.6f ], point("10.1,11.1"), line("10.1,11.1 10.2,11.2"), polygon("1.2,1.3 2.1,2.5 3.5,3.6 4.6,4.8"), null ], "item1": [ "1.0f", "yassser" ], "item2": [ 11, 14, "yasir", 1.6f ], "item5": null, "item10": null }
+{ "orderid": 10, "ordertot": 7.206f, "list": [ [ 1.0f, "5.2f", "60" ], [ 13231, "foo", null, 13.25d, 13.2f ], point("10.1,11.1"), line("10.1,11.1 10.2,11.2"), polygon("1.2,1.3 2.1,2.5 3.5,3.6 4.6,4.8"), null ], "item1": [ 1.0f, "5.2f", "60" ], "item2": [ 13231, "foo", null, 13.25d, 13.2f ], "item5": null, "item10": null }
+{ "orderid": 100, "ordertot": 124.26f, "list": [ [ 1.3f, 5.2f, "60", 12.32f ], [ 10, 2.0f, 3.0d, 40 ], point("10.1,11.1"), line("10.1,11.1 10.2,11.2"), polygon("1.2,1.3 2.1,2.5 3.5,3.6 4.6,4.8"), null ], "item1": [ 1.3f, 5.2f, "60", 12.32f ], "item2": [ 10, 2.0f, 3.0d, 40 ], "item5": null, "item10": null }
+{ "orderid": 10, "ordertot": 14.2326f, "list": [ [ 2.4f, "15" ], [ 110 ], point("10.1,11.1"), line("10.1,11.1 10.2,11.2"), polygon("1.2,1.3 2.1,2.5 3.5,3.6 4.6,4.8"), { "oid": 75, "total": 87.61863f } ], "item1": [ 2.4f, "15" ], "item2": [ 110 ], "item5": { "oid": 75, "total": 87.61863f }, "item10": null }
diff --git a/asterix-app/src/test/resources/runtimets/results/custord/order_q_05.adm b/asterix-app/src/test/resources/runtimets/results/custord/order_q_05.adm
index dd3420e..4d8b37c 100644
--- a/asterix-app/src/test/resources/runtimets/results/custord/order_q_05.adm
+++ b/asterix-app/src/test/resources/runtimets/results/custord/order_q_05.adm
@@ -1,4 +1,4 @@
-{ "orderid": 1000, "ordertot": 97.20656f, "emptyorderedlist": [  ], "emptyunorderedlist": {{  }}, "olist_item1": null, "olist_item1": null, "olist_item5": null, "ulist_item1": null }
-{ "orderid": 10, "ordertot": 7.206f, "emptyorderedlist": [  ], "emptyunorderedlist": {{  }}, "olist_item1": null, "olist_item1": null, "olist_item5": null, "ulist_item1": null }
-{ "orderid": 100, "ordertot": 124.26f, "emptyorderedlist": [  ], "emptyunorderedlist": {{  }}, "olist_item1": null, "olist_item1": null, "olist_item5": null, "ulist_item1": null }
-{ "orderid": 10, "ordertot": 14.2326f, "emptyorderedlist": [  ], "emptyunorderedlist": {{  }}, "olist_item1": null, "olist_item1": null, "olist_item5": null, "ulist_item1": null }
+{ "orderid": 1000, "ordertot": 97.20656f, "emptyorderedlist": [  ], "emptyunorderedlist": {{  }}, "olist_item1": null, "olist_item5": null, "ulist_item1": null }
+{ "orderid": 10, "ordertot": 7.206f, "emptyorderedlist": [  ], "emptyunorderedlist": {{  }}, "olist_item1": null, "olist_item5": null, "ulist_item1": null }
+{ "orderid": 100, "ordertot": 124.26f, "emptyorderedlist": [  ], "emptyunorderedlist": {{  }}, "olist_item1": null, "olist_item5": null, "ulist_item1": null }
+{ "orderid": 10, "ordertot": 14.2326f, "emptyorderedlist": [  ], "emptyunorderedlist": {{  }}, "olist_item1": null, "olist_item5": null, "ulist_item1": null }
diff --git a/asterix-om/src/main/java/edu/uci/ics/asterix/builders/IARecordBuilder.java b/asterix-om/src/main/java/edu/uci/ics/asterix/builders/IARecordBuilder.java
index 544b532..cb7f902 100644
--- a/asterix-om/src/main/java/edu/uci/ics/asterix/builders/IARecordBuilder.java
+++ b/asterix-om/src/main/java/edu/uci/ics/asterix/builders/IARecordBuilder.java
@@ -18,7 +18,9 @@
 import java.io.DataOutput;
 import java.io.IOException;
 
+import edu.uci.ics.asterix.common.exceptions.AsterixException;
 import edu.uci.ics.asterix.om.types.ARecordType;
+import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
 import edu.uci.ics.hyracks.data.std.api.IValueReference;
 
 /**
@@ -59,8 +61,9 @@
      *            Whether to write a typetag as part of the record's serialized
      *            representation.
      * @throws IOException
+     * @throws AsterixException
      */
-    public void write(DataOutput out, boolean writeTypeTag) throws IOException;
+    public void write(DataOutput out, boolean writeTypeTag) throws IOException, HyracksDataException;
 
     public int getFieldId(String fieldName);
 
diff --git a/asterix-om/src/main/java/edu/uci/ics/asterix/builders/RecordBuilder.java b/asterix-om/src/main/java/edu/uci/ics/asterix/builders/RecordBuilder.java
index 03f0e20..92c03b1 100644
--- a/asterix-om/src/main/java/edu/uci/ics/asterix/builders/RecordBuilder.java
+++ b/asterix-om/src/main/java/edu/uci/ics/asterix/builders/RecordBuilder.java
@@ -1,6 +1,8 @@
 package edu.uci.ics.asterix.builders;
 
+import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
+import java.io.DataInputStream;
 import java.io.DataOutput;
 import java.io.IOException;
 import java.util.Arrays;
@@ -9,32 +11,21 @@
 import edu.uci.ics.asterix.om.types.ARecordType;
 import edu.uci.ics.asterix.om.types.ATypeTag;
 import edu.uci.ics.asterix.om.util.NonTaggedFormatUtil;
+import edu.uci.ics.hyracks.api.dataflow.value.IBinaryComparator;
 import edu.uci.ics.hyracks.api.dataflow.value.IBinaryHashFunction;
+import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
+import edu.uci.ics.hyracks.data.std.accessors.PointableBinaryComparatorFactory;
 import edu.uci.ics.hyracks.data.std.accessors.PointableBinaryHashFunctionFactory;
 import edu.uci.ics.hyracks.data.std.api.IValueReference;
 import edu.uci.ics.hyracks.data.std.primitive.UTF8StringPointable;
+import edu.uci.ics.hyracks.data.std.util.ByteArrayAccessibleOutputStream;
+import edu.uci.ics.hyracks.dataflow.common.data.marshalling.UTF8StringSerializerDeserializer;
 
 public class RecordBuilder implements IARecordBuilder {
-    private int openPartOffset;
+    private final static int DEFAULT_NUM_OPEN_FIELDS = 10;
+    private final static byte SER_NULL_TYPE_TAG = ATypeTag.NULL.serialize();
+    private final static byte RECORD_TYPE_TAG = ATypeTag.RECORD.serialize();
 
-    private ARecordType recType;
-
-    private ByteArrayOutputStream closedPartOutputStream;
-    private int[] closedPartOffsets;
-    private int numberOfClosedFields;
-    private byte[] nullBitMap;
-    private int nullBitMapSize;
-
-    private ByteArrayOutputStream openPartOutputStream;
-    private long[] openPartOffsets;
-    private long[] tempOpenPartOffsets;
-
-    private int numberOfOpenFields;
-
-    private int fieldNameHashCode;
-    private final IBinaryHashFunction utf8HashFunction;
-
-    // for write()
     private int openPartOffsetArraySize;
     private byte[] openPartOffsetArray;
     private int offsetPosition;
@@ -42,25 +33,40 @@
     private boolean isOpen;
     private boolean isNullable;
     private int numberOfSchemaFields;
-    private final static byte SER_NULL_TYPE_TAG = ATypeTag.NULL.serialize();
-    private final static byte RECORD_TYPE_TAG = ATypeTag.RECORD.serialize();
+
+    private int openPartOffset;
+    private ARecordType recType;
+
+    private final IBinaryHashFunction utf8HashFunction;
+    private final IBinaryComparator utf8Comparator;
+
+    private final ByteArrayOutputStream closedPartOutputStream;
+    private int[] closedPartOffsets;
+    private int numberOfClosedFields;
+    private byte[] nullBitMap;
+    private int nullBitMapSize;
+
+    private final ByteArrayAccessibleOutputStream openPartOutputStream;
+    private long[] openPartOffsets;
+    private int[] openFieldNameLengths;
+
+    private int numberOfOpenFields;
 
     public RecordBuilder() {
 
         this.closedPartOutputStream = new ByteArrayOutputStream();
         this.numberOfClosedFields = 0;
 
-        this.openPartOutputStream = new ByteArrayOutputStream();
-        this.openPartOffsets = new long[20];
-        this.tempOpenPartOffsets = new long[20];
-
+        this.openPartOutputStream = new ByteArrayAccessibleOutputStream();
+        this.openPartOffsets = new long[DEFAULT_NUM_OPEN_FIELDS];
+        this.openFieldNameLengths = new int[DEFAULT_NUM_OPEN_FIELDS];
         this.numberOfOpenFields = 0;
 
-        this.fieldNameHashCode = 0;
         this.utf8HashFunction = new PointableBinaryHashFunctionFactory(UTF8StringPointable.FACTORY)
                 .createBinaryHashFunction();
+        this.utf8Comparator = new PointableBinaryComparatorFactory(UTF8StringPointable.FACTORY)
+                .createBinaryComparator();
 
-        // for write()
         this.openPartOffsetArray = null;
         this.openPartOffsetArraySize = 0;
         this.offsetPosition = 0;
@@ -137,21 +143,21 @@
     @Override
     public void addField(IValueReference name, IValueReference value) {
         if (numberOfOpenFields == openPartOffsets.length) {
-            tempOpenPartOffsets = openPartOffsets;
-            openPartOffsets = new long[numberOfOpenFields + 20];
-            for (int i = 0; i < tempOpenPartOffsets.length; i++)
-                openPartOffsets[i] = tempOpenPartOffsets[i];
+            openPartOffsets = Arrays.copyOf(openPartOffsets, openPartOffsets.length + DEFAULT_NUM_OPEN_FIELDS);
+            openFieldNameLengths = Arrays.copyOf(openFieldNameLengths, openFieldNameLengths.length
+                    + DEFAULT_NUM_OPEN_FIELDS);
         }
-        fieldNameHashCode = utf8HashFunction.hash(name.getByteArray(), name.getStartOffset() + 1, name.getLength());
+        int fieldNameHashCode = utf8HashFunction.hash(name.getByteArray(), name.getStartOffset() + 1, name.getLength());
         openPartOffsets[this.numberOfOpenFields] = fieldNameHashCode;
         openPartOffsets[this.numberOfOpenFields] = (openPartOffsets[numberOfOpenFields] << 32);
-        openPartOffsets[numberOfOpenFields++] += openPartOutputStream.size();
+        openPartOffsets[numberOfOpenFields] += openPartOutputStream.size();
+        openFieldNameLengths[numberOfOpenFields++] = name.getLength() - 1;
         openPartOutputStream.write(name.getByteArray(), name.getStartOffset() + 1, name.getLength() - 1);
         openPartOutputStream.write(value.getByteArray(), value.getStartOffset(), value.getLength());
     }
 
     @Override
-    public void write(DataOutput out, boolean writeTypeTag) throws IOException {
+    public void write(DataOutput out, boolean writeTypeTag) throws HyracksDataException, IOException {
         int h = headerSize;
         int recordLength;
         // prepare the open part
@@ -163,13 +169,27 @@
                 openPartOffsetArray = new byte[openPartOffsetArraySize];
 
             Arrays.sort(this.openPartOffsets, 0, numberOfOpenFields);
+            if (numberOfOpenFields > 1) {
+                byte[] openBytes = openPartOutputStream.getByteArray();
+                for (int i = 1; i < numberOfOpenFields; i++) {
+                    if (utf8Comparator.compare(openBytes, (int) openPartOffsets[i - 1], openFieldNameLengths[i - 1],
+                            openBytes, (int) openPartOffsets[i], openFieldNameLengths[i]) == 0) {
+                        String field = UTF8StringSerializerDeserializer.INSTANCE
+                                .deserialize(new DataInputStream(new ByteArrayInputStream(openBytes,
+                                        (int) openPartOffsets[i], openFieldNameLengths[i])));
+                        throw new HyracksDataException("Open fields " + (i - 1) + " and " + i
+                                + " have the same field name \"" + field + "\"");
+                    }
+                }
+            }
 
             openPartOffset = h + numberOfSchemaFields * 4 + closedPartOutputStream.size();
+            int fieldNameHashCode;
             for (int i = 0; i < numberOfOpenFields; i++) {
                 fieldNameHashCode = (int) (openPartOffsets[i] >> 32);
                 SerializerDeserializerUtil.writeIntToByteArray(openPartOffsetArray, (int) fieldNameHashCode,
                         offsetPosition);
-                int fieldOffset = (int) ((openPartOffsets[i] << 64) >> 64);
+                int fieldOffset = (int) openPartOffsets[i];
                 SerializerDeserializerUtil.writeIntToByteArray(openPartOffsetArray, fieldOffset + openPartOffset + 4
                         + openPartOffsetArraySize, offsetPosition + 4);
                 offsetPosition += 8;