@Override
    public boolean evaluate(Tuple tuple, ImmutableBytesWritable ptr) {
        Object[] elements = new Object[children.size()];
        for (int i = 0; i < children.size(); i++) {
            Expression child = children.get(i);
            if (!child.evaluate(tuple, ptr)) {
                return false;
            } else {
                elements[i] = baseType.toObject(ptr, child.getDataType(), child.getColumnModifier());
            }
        }
        PhoenixArray array = PArrayDataType.instantiatePhoenixArray(baseType, elements);
        return true;
    }
See my code.. This is done. But I get a failure after this step where we try to build the array using the toObject
     java.nio.BufferUnderflowException
	at java.nio.Buffer.nextGetIndex(Unknown Source)
	at java.nio.HeapByteBuffer.getInt(Unknown Source)
	at com.salesforce.phoenix.schema.PArrayDataType.createPhoenixArray(PArrayDataType.java:313)
	at com.salesforce.phoenix.schema.PArrayDataType.toObject(PArrayDataType.java:146)
	at com.salesforce.phoenix.schema.PDataType$25.toObject(PDataType.java:3502)
	at com.salesforce.phoenix.schema.PDataType.toObject(PDataType.java:6863)
	at com.salesforce.phoenix.compile.ExpressionProjector.getValue(ExpressionProjector.java:86)
	at com.salesforce.phoenix.jdbc.PhoenixResultSet.getArray(PhoenixResultSet.java:176)
	at com.salesforce.phoenix.end2end.ArrayTest.testUpsertSelectWithSelectAsSubQuery2(ArrayTest.java:447)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)