diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/translator/util/ValidateUtil.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/translator/util/ValidateUtil.java
index 4b4b2b0..d5ebc6e 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/translator/util/ValidateUtil.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/translator/util/ValidateUtil.java
@@ -131,11 +131,19 @@
         } else {
             partitioningExprTypes =
                     KeyFieldTypeUtil.getKeyTypes(recType, metaRecType, partitioningExprs, keySourceIndicators);
-            for (int fidx = 0; fidx < partitioningExprTypes.size(); ++fidx) {
-                IAType fieldType = partitioningExprTypes.get(fidx);
+            for (int i = 0; i < partitioningExprs.size(); i++) {
+                List<String> partitioningExpr = partitioningExprs.get(i);
+                IAType fieldType = partitioningExprTypes.get(i);
                 if (fieldType == null) {
                     throw new CompilationException(ErrorCode.COMPILATION_FIELD_NOT_FOUND,
-                            RecordUtil.toFullyQualifiedName(partitioningExprs.get(fidx)));
+                            RecordUtil.toFullyQualifiedName(partitioningExpr));
+                }
+                boolean nullable = KeyFieldTypeUtil.chooseSource(keySourceIndicators, i, recType, metaRecType)
+                        .isSubFieldNullable(partitioningExpr);
+                if (nullable) {
+                    // key field is nullable
+                    throw new CompilationException(ErrorCode.COMPILATION_PRIMARY_KEY_CANNOT_BE_NULLABLE,
+                            RecordUtil.toFullyQualifiedName(partitioningExpr));
                 }
                 switch (fieldType.getTypeTag()) {
                     case TINYINT:
@@ -155,7 +163,7 @@
                         break;
                     case UNION:
                         throw new CompilationException(ErrorCode.COMPILATION_PRIMARY_KEY_CANNOT_BE_NULLABLE,
-                                RecordUtil.toFullyQualifiedName(partitioningExprs.get(fidx)));
+                                RecordUtil.toFullyQualifiedName(partitioningExpr));
                     default:
                         throw new CompilationException(ErrorCode.COMPILATION_ILLEGAL_PRIMARY_KEY_TYPE,
                                 fieldType.getTypeTag());
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nested-index/index-selection/rtree-secondary-index-optional/rtree-secondary-index-optional.1.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nested-index/index-selection/rtree-secondary-index-optional/rtree-secondary-index-optional.1.ddl.sqlpp
new file mode 100644
index 0000000..f650e0a
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nested-index/index-selection/rtree-secondary-index-optional/rtree-secondary-index-optional.1.ddl.sqlpp
@@ -0,0 +1,47 @@
+/*
+ * 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.
+ */
+
+drop  dataverse test if exists;
+create  dataverse test;
+
+use test;
+
+
+create type test.MyRecordtmp as
+{
+  id : bigint,
+  point : point,
+  kwds : string,
+  line1 : line,
+  line2 : line,
+  poly1 : polygon,
+  poly2 : polygon,
+  rec : rectangle
+};
+
+create type test.MyRecord as
+{
+  pid: uuid,
+  nested : MyRecordtmp?
+};
+
+create  dataset MyDatatmp(MyRecordtmp) primary key id;
+
+create  dataset MyData(MyRecord) primary key pid autogenerated;
+
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nested-index/index-selection/rtree-secondary-index-optional/rtree-secondary-index-optional.2.update.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nested-index/index-selection/rtree-secondary-index-optional/rtree-secondary-index-optional.2.update.sqlpp
new file mode 100644
index 0000000..8199dbd
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nested-index/index-selection/rtree-secondary-index-optional/rtree-secondary-index-optional.2.update.sqlpp
@@ -0,0 +1,28 @@
+/*
+ * 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.
+ */
+
+use test;
+
+
+load  dataset MyDatatmp using localfs ((`path`=`asterix_nc1://data/spatial/spatialData.json`),(`format`=`adm`));
+
+insert into MyData
+select element {'nested':c}
+from  MyDatatmp as c
+;
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nested-index/index-selection/rtree-secondary-index-optional/rtree-secondary-index-optional.3.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nested-index/index-selection/rtree-secondary-index-optional/rtree-secondary-index-optional.3.ddl.sqlpp
new file mode 100644
index 0000000..5683fe0
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nested-index/index-selection/rtree-secondary-index-optional/rtree-secondary-index-optional.3.ddl.sqlpp
@@ -0,0 +1,24 @@
+/*
+ * 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.
+ */
+
+use test;
+
+
+create  index rtree_index_point  on MyData (nested.point) type rtree;
+
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nested-index/index-selection/rtree-secondary-index-optional/rtree-secondary-index-optional.4.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nested-index/index-selection/rtree-secondary-index-optional/rtree-secondary-index-optional.4.query.sqlpp
new file mode 100644
index 0000000..93665a4
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nested-index/index-selection/rtree-secondary-index-optional/rtree-secondary-index-optional.4.query.sqlpp
@@ -0,0 +1,27 @@
+/*
+ * 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.
+ */
+
+use test;
+
+
+select element {'id':o.nested.id}
+from  MyData as o
+where test.`spatial-intersect`(o.nested.point,test.`create-polygon`([4.0,1.0,4.0,4.0,12.0,4.0,12.0,1.0]))
+order by o.nested.id
+;
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nestrecords/nested-optional-pk/nested-optional-pk.1.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nestrecords/nested-optional-pk/nested-optional-pk.1.ddl.sqlpp
new file mode 100644
index 0000000..c4af7d8
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/nestrecords/nested-optional-pk/nested-optional-pk.1.ddl.sqlpp
@@ -0,0 +1,37 @@
+/*
+ * 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.
+ */
+
+drop  dataverse test if exists;
+create  dataverse test;
+
+use test;
+
+
+create type test.MyRecordtmp as
+{
+  id : bigint,
+  point : point
+};
+
+create type test.MyRecord as
+{
+  nested : MyRecordtmp?
+};
+
+create  dataset MyData(MyRecord) primary key nested.id;
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml
index 95c059d..e545c3b 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml
@@ -4399,6 +4399,11 @@
           <output-dir compare="Text">rtree-secondary-index-open</output-dir>
         </compilation-unit>
       </test-case>
+      <test-case FilePath="nested-index/index-selection">
+        <compilation-unit name="rtree-secondary-index-optional">
+          <output-dir compare="Text">rtree-secondary-index-open</output-dir>
+        </compilation-unit>
+      </test-case>
     </test-group>
     <test-group name="nested-index/external-indexing">
       <test-case FilePath="nested-index/external-indexing">
@@ -4581,6 +4586,12 @@
         <output-dir compare="Text">nestrecord</output-dir>
       </compilation-unit>
     </test-case>
+    <test-case FilePath="nestrecords">
+      <compilation-unit name="nested-optional-pk">
+        <output-dir compare="Text">nested-optional-pk</output-dir>
+        <expected-error>ASX1021: The primary key field "nested.id" cannot be nullable</expected-error>
+      </compilation-unit>
+    </test-case>
   </test-group>
   <test-group name="null-missing">
     <test-case FilePath="null-missing">
diff --git a/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/entities/Index.java b/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/entities/Index.java
index bf19b03..3159030 100644
--- a/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/entities/Index.java
+++ b/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/entities/Index.java
@@ -22,6 +22,7 @@
 import java.util.List;
 
 import org.apache.asterix.common.config.DatasetConfig.IndexType;
+import org.apache.asterix.common.exceptions.AsterixException;
 import org.apache.asterix.common.exceptions.CompilationException;
 import org.apache.asterix.common.exceptions.ErrorCode;
 import org.apache.asterix.common.transactions.IRecoveryManager.ResourceType;
@@ -153,8 +154,18 @@
             ARecordType recType) throws AlgebricksException {
         Pair<IAType, Boolean> keyPairType = null;
         IAType subType = recType;
+        boolean nullable = false;
         for (int i = 0; i < fieldName.size(); i++) {
-            subType = ((ARecordType) subType).getFieldType(fieldName.get(i));
+            if (subType instanceof AUnionType) {
+                nullable = nullable || ((AUnionType) subType).isUnknownableType();
+                subType = ((AUnionType) subType).getActualType();
+            }
+            if (subType instanceof ARecordType) {
+                subType = ((ARecordType) subType).getFieldType(fieldName.get(i));
+            } else {
+                throw AsterixException.create(ErrorCode.COMPILATION_ILLEGAL_STATE, "Unexpected type " + fieldType);
+            }
+
             if (subType == null) {
                 keyPairType = Index.getNonNullableType(fieldType);
                 break;
@@ -163,13 +174,16 @@
         if (subType != null) {
             keyPairType = Index.getNonNullableKeyFieldType(fieldName, recType);
         }
+        keyPairType.second = keyPairType.second || nullable;
         return keyPairType;
     }
 
     public static Pair<IAType, Boolean> getNonNullableKeyFieldType(List<String> expr, ARecordType recType)
             throws AlgebricksException {
         IAType keyType = Index.keyFieldType(expr, recType);
-        return getNonNullableType(keyType);
+        Pair<IAType, Boolean> pair = getNonNullableType(keyType);
+        pair.second = pair.second || recType.isSubFieldNullable(expr);
+        return pair;
     }
 
     private static IAType keyFieldType(List<String> expr, ARecordType recType) throws AlgebricksException {
diff --git a/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/types/ARecordType.java b/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/types/ARecordType.java
index baaed59..26cbf1f 100644
--- a/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/types/ARecordType.java
+++ b/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/types/ARecordType.java
@@ -28,7 +28,10 @@
 
 import org.apache.asterix.common.annotations.IRecordTypeAnnotation;
 import org.apache.asterix.common.exceptions.AsterixException;
+import org.apache.asterix.common.exceptions.CompilationException;
+import org.apache.asterix.common.exceptions.ErrorCode;
 import org.apache.asterix.om.base.IAObject;
+import org.apache.asterix.om.utils.NonTaggedFormatUtil;
 import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -226,6 +229,39 @@
     }
 
     /**
+     *
+     * @param subFieldName
+     *            The full pathname of the field
+     * @return The nullability of the field
+     * @throws AlgebricksException
+     */
+    public boolean isSubFieldNullable(List<String> subFieldName) throws AlgebricksException {
+        IAType subRecordType = getFieldType(subFieldName.get(0));
+        for (int i = 1; i < subFieldName.size(); i++) {
+            if (subRecordType == null) {
+                // open field is nullable
+                return true;
+            }
+            if (subRecordType.getTypeTag().equals(ATypeTag.UNION)) {
+                if (NonTaggedFormatUtil.isOptional(subRecordType)) {
+                    return true;
+                }
+                subRecordType = ((AUnionType) subRecordType).getActualType();
+                if (subRecordType.getTypeTag() != ATypeTag.OBJECT) {
+                    throw new AsterixException(
+                            "Field accessor is not defined for values of type " + subRecordType.getTypeTag());
+                }
+            }
+            if (!(subRecordType instanceof ARecordType)) {
+                throw CompilationException.create(ErrorCode.COMPILATION_ILLEGAL_STATE,
+                        "Illegal field type " + subRecordType.getTypeTag() + " when checking field nullability");
+            }
+            subRecordType = ((ARecordType) subRecordType).getFieldType(subFieldName.get(i));
+        }
+        return subRecordType == null || NonTaggedFormatUtil.isOptional(subRecordType);
+    }
+
+    /**
      * Returns the field type of the field name if it exists, otherwise null.
      *
      * @param fieldName