diff --git a/presto-main/src/main/java/com/facebook/presto/metadata/PolymorphicScalarFunction.java b/presto-main/src/main/java/com/facebook/presto/metadata/PolymorphicScalarFunction.java
index d8ef8cb8c95d..08d92bf5bf52 100644
--- a/presto-main/src/main/java/com/facebook/presto/metadata/PolymorphicScalarFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/metadata/PolymorphicScalarFunction.java
@@ -34,7 +34,6 @@
 import static com.facebook.presto.operator.scalar.ScalarFunctionImplementation.NullConvention.USE_BOXED_TYPE;
 import static com.facebook.presto.operator.scalar.ScalarFunctionImplementation.NullConvention.USE_NULL_FLAG;
 import static com.facebook.presto.type.TypeUtils.resolveTypes;
-import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkState;
 import static java.util.Collections.emptyList;
 import static java.util.Objects.requireNonNull;
@@ -186,7 +185,6 @@ private static Class<?> getNullAwareContainerType(Class<?> clazz, boolean nullab
         if (nullable) {
             return Primitives.wrap(clazz);
         }
-        checkArgument(clazz != void.class);
         return clazz;
     }
 }
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/AbstractMinMaxAggregationFunction.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/AbstractMinMaxAggregationFunction.java
index 996d99b92586..722b3697ee9a 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/AbstractMinMaxAggregationFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/AbstractMinMaxAggregationFunction.java
@@ -55,20 +55,17 @@
 public abstract class AbstractMinMaxAggregationFunction
         extends SqlAggregationFunction
 {
-    private static final MethodHandle UNKNOWN_INPUT_FUNCTION = methodHandle(AbstractMinMaxAggregationFunction.class, "input", AccumulatorState.class, Block.class, int.class);
     private static final MethodHandle LONG_INPUT_FUNCTION = methodHandle(AbstractMinMaxAggregationFunction.class, "input", MethodHandle.class, NullableLongState.class, long.class);
     private static final MethodHandle DOUBLE_INPUT_FUNCTION = methodHandle(AbstractMinMaxAggregationFunction.class, "input", MethodHandle.class, NullableDoubleState.class, double.class);
     private static final MethodHandle BOOLEAN_INPUT_FUNCTION = methodHandle(AbstractMinMaxAggregationFunction.class, "input", MethodHandle.class, NullableBooleanState.class, boolean.class);
     private static final MethodHandle BLOCK_POSITION_MIN_INPUT_FUNCTION = methodHandle(AbstractMinMaxAggregationFunction.class, "minInput", Type.class, BlockPositionState.class, Block.class, int.class);
     private static final MethodHandle BLOCK_POSITION_MAX_INPUT_FUNCTION = methodHandle(AbstractMinMaxAggregationFunction.class, "maxInput", Type.class, BlockPositionState.class, Block.class, int.class);
 
-    private static final MethodHandle UNKNOWN_OUTPUT_FUNCTION = methodHandle(AbstractMinMaxAggregationFunction.class, "writeNull", AccumulatorState.class, BlockBuilder.class);
     private static final MethodHandle LONG_OUTPUT_FUNCTION = methodHandle(NullableLongState.class, "write", Type.class, NullableLongState.class, BlockBuilder.class);
     private static final MethodHandle DOUBLE_OUTPUT_FUNCTION = methodHandle(NullableDoubleState.class, "write", Type.class, NullableDoubleState.class, BlockBuilder.class);
     private static final MethodHandle BOOLEAN_OUTPUT_FUNCTION = methodHandle(NullableBooleanState.class, "write", Type.class, NullableBooleanState.class, BlockBuilder.class);
     private static final MethodHandle BLOCK_POSITION_OUTPUT_FUNCTION = methodHandle(BlockPositionState.class, "write", Type.class, BlockPositionState.class, BlockBuilder.class);
 
-    private static final MethodHandle UNKNOWN_COMBINE_FUNCTION = methodHandle(AbstractMinMaxAggregationFunction.class, "combine", AccumulatorState.class, AccumulatorState.class);
     private static final MethodHandle LONG_COMBINE_FUNCTION = methodHandle(AbstractMinMaxAggregationFunction.class, "combine", MethodHandle.class, NullableLongState.class, NullableLongState.class);
     private static final MethodHandle DOUBLE_COMBINE_FUNCTION = methodHandle(AbstractMinMaxAggregationFunction.class, "combine", MethodHandle.class, NullableDoubleState.class, NullableDoubleState.class);
     private static final MethodHandle BOOLEAN_COMBINE_FUNCTION = methodHandle(AbstractMinMaxAggregationFunction.class, "combine", MethodHandle.class, NullableBooleanState.class, NullableBooleanState.class);
@@ -109,14 +106,7 @@ protected InternalAggregationFunction generateAggregation(Type type, MethodHandl
         Class<? extends AccumulatorState> stateInterface;
         AccumulatorStateSerializer<?> stateSerializer;
 
-        if (type.getJavaType() == void.class) {
-            stateInterface = AccumulatorState.class;
-            stateSerializer = StateCompiler.generateStateSerializer(stateInterface, classLoader);
-            inputFunction = UNKNOWN_INPUT_FUNCTION;
-            combineFunction = UNKNOWN_COMBINE_FUNCTION;
-            outputFunction = UNKNOWN_OUTPUT_FUNCTION;
-        }
-        else if (type.getJavaType() == long.class) {
+        if (type.getJavaType() == long.class) {
             stateInterface = NullableLongState.class;
             stateSerializer = StateCompiler.generateStateSerializer(stateInterface, classLoader);
             inputFunction = LONG_INPUT_FUNCTION.bindTo(compareMethodHandle);
@@ -166,7 +156,7 @@ else if (type.getJavaType() == boolean.class) {
 
     private static List<ParameterMetadata> createParameterMetadata(Type type)
     {
-        if (type.getJavaType().isPrimitive() && type.getJavaType() != void.class) {
+        if (type.getJavaType().isPrimitive()) {
             return ImmutableList.of(
                     new ParameterMetadata(STATE),
                     new ParameterMetadata(INPUT_CHANNEL, type));
@@ -179,11 +169,6 @@ private static List<ParameterMetadata> createParameterMetadata(Type type)
         }
     }
 
-    public static void input(AccumulatorState state, Block block, int position)
-    {
-        // Do nothing
-    }
-
     public static void input(MethodHandle methodHandle, NullableDoubleState state, double value)
     {
         compareAndUpdateState(methodHandle, state, value);
@@ -215,11 +200,6 @@ public static void maxInput(Type type, BlockPositionState state, Block block, in
         }
     }
 
-    public static void combine(AccumulatorState state, AccumulatorState otherState)
-    {
-        // Do nothing
-    }
-
     public static void combine(MethodHandle methodHandle, NullableLongState state, NullableLongState otherState)
     {
         compareAndUpdateState(methodHandle, state, otherState.getLong());
@@ -251,11 +231,6 @@ public static void maxCombine(Type type, BlockPositionState state, BlockPosition
         }
     }
 
-    public static void writeNull(AccumulatorState state, BlockBuilder out)
-    {
-        out.appendNull();
-    }
-
     private static void compareAndUpdateState(MethodHandle methodHandle, NullableLongState state, long value)
     {
         if (state.isNull()) {
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/BlockUnknownState.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/BlockUnknownState.java
deleted file mode 100644
index 149fcdf2bc2d..000000000000
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/BlockUnknownState.java
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * Licensed 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 com.facebook.presto.operator.aggregation.minmaxby;
-
-import com.facebook.presto.spi.block.Block;
-
-public interface BlockUnknownState
-        extends TwoNullableValueState
-{
-    Block getFirst();
-
-    void setFirst(Block first);
-
-    // Second state is void and will always be null
-}
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/BooleanUnknownState.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/BooleanUnknownState.java
deleted file mode 100644
index c2b095032eda..000000000000
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/BooleanUnknownState.java
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Licensed 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 com.facebook.presto.operator.aggregation.minmaxby;
-
-public interface BooleanUnknownState
-        extends TwoNullableValueState
-{
-    boolean getFirst();
-
-    void setFirst(boolean first);
-
-    // Second state is void and will always be null
-}
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/DoubleUnknownState.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/DoubleUnknownState.java
deleted file mode 100644
index 348359c2ebf3..000000000000
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/DoubleUnknownState.java
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Licensed 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 com.facebook.presto.operator.aggregation.minmaxby;
-
-public interface DoubleUnknownState
-        extends TwoNullableValueState
-{
-    double getFirst();
-
-    void setFirst(double first);
-
-    // Second state is void and will always be null
-}
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/LongUnknownState.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/LongUnknownState.java
deleted file mode 100644
index e1a613148bfb..000000000000
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/LongUnknownState.java
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Licensed 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 com.facebook.presto.operator.aggregation.minmaxby;
-
-public interface LongUnknownState
-        extends TwoNullableValueState
-{
-    long getFirst();
-
-    void setFirst(long first);
-
-    // Second state is void and will always be null
-}
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/SliceUnknownState.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/SliceUnknownState.java
deleted file mode 100644
index 373a2894bc39..000000000000
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/SliceUnknownState.java
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * Licensed 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 com.facebook.presto.operator.aggregation.minmaxby;
-
-import io.airlift.slice.Slice;
-
-public interface SliceUnknownState
-        extends TwoNullableValueState
-{
-    Slice getFirst();
-
-    void setFirst(Slice first);
-
-    // Second state is void and will always be null
-}
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/TwoNullableValueStateMapping.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/TwoNullableValueStateMapping.java
index 37d401433cfe..3cc061402bd0 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/TwoNullableValueStateMapping.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/TwoNullableValueStateMapping.java
@@ -40,37 +40,26 @@ private TwoNullableValueStateMapping() {}
                 .put(ImmutableList.of(boolean.class, double.class), BooleanDoubleState.class)
                 .put(ImmutableList.of(boolean.class, long.class), BooleanLongState.class)
                 .put(ImmutableList.of(boolean.class, Slice.class), BooleanAndBlockPositionValueState.class)
-                .put(ImmutableList.of(boolean.class, void.class), BooleanUnknownState.class)
                 .put(ImmutableList.of(double.class, boolean.class), DoubleBooleanState.class)
                 .put(ImmutableList.of(double.class, Block.class), DoubleAndBlockPositionValueState.class)
                 .put(ImmutableList.of(double.class, double.class), DoubleDoubleState.class)
                 .put(ImmutableList.of(double.class, long.class), DoubleLongState.class)
                 .put(ImmutableList.of(double.class, Slice.class), DoubleAndBlockPositionValueState.class)
-                .put(ImmutableList.of(double.class, void.class), DoubleUnknownState.class)
                 .put(ImmutableList.of(long.class, Block.class), LongAndBlockPositionValueState.class)
                 .put(ImmutableList.of(long.class, boolean.class), LongBooleanState.class)
                 .put(ImmutableList.of(long.class, double.class), LongDoubleState.class)
                 .put(ImmutableList.of(long.class, long.class), LongLongState.class)
                 .put(ImmutableList.of(long.class, Slice.class), LongAndBlockPositionValueState.class)
-                .put(ImmutableList.of(long.class, void.class), LongUnknownState.class)
                 .put(ImmutableList.of(Slice.class, boolean.class), SliceBooleanState.class)
                 .put(ImmutableList.of(Slice.class, Block.class), SliceAndBlockPositionValueState.class)
                 .put(ImmutableList.of(Slice.class, double.class), SliceDoubleState.class)
                 .put(ImmutableList.of(Slice.class, long.class), SliceLongState.class)
                 .put(ImmutableList.of(Slice.class, Slice.class), SliceAndBlockPositionValueState.class)
-                .put(ImmutableList.of(Slice.class, void.class), SliceUnknownState.class)
                 .put(ImmutableList.of(Block.class, boolean.class), BlockBooleanState.class)
                 .put(ImmutableList.of(Block.class, Block.class), BlockAndBlockPositionValueState.class)
                 .put(ImmutableList.of(Block.class, double.class), BlockDoubleState.class)
                 .put(ImmutableList.of(Block.class, long.class), BlockLongState.class)
                 .put(ImmutableList.of(Block.class, Slice.class), BlockAndBlockPositionValueState.class)
-                .put(ImmutableList.of(Block.class, void.class), BlockUnknownState.class)
-                .put(ImmutableList.of(void.class, void.class), TwoNullableValueState.class)
-                .put(ImmutableList.of(void.class, Block.class), KeyAndBlockPositionValueState.class)  // no need to specify the first field if it is unknown
-                .put(ImmutableList.of(void.class, boolean.class), UnknownBooleanState.class)
-                .put(ImmutableList.of(void.class, double.class), UnknownDoubleState.class)
-                .put(ImmutableList.of(void.class, long.class), UnknownLongState.class)
-                .put(ImmutableList.of(void.class, Slice.class), KeyAndBlockPositionValueState.class)  // no need to specify the first field if it is unknown
                 .build();
     }
 
@@ -105,9 +94,6 @@ public static AccumulatorStateSerializer<?> getStateSerializer(Type firstType, T
         if (firstJavaType == Block.class) {
             return new BlockAndBlockPositionStateSerializer(firstType, secondType);
         }
-        if (firstJavaType == void.class) {
-            return new UnknownAndBlockPositionStateSerializer(firstType, secondType);
-        }
         throw new IllegalArgumentException(format("Unsupported state type combination: (%s, %s)", firstJavaType.getName(), secondJavaType.getName()));
     }
 }
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/UnknownAndBlockPositionStateSerializer.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/UnknownAndBlockPositionStateSerializer.java
deleted file mode 100644
index 955907faa599..000000000000
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/UnknownAndBlockPositionStateSerializer.java
+++ /dev/null
@@ -1,39 +0,0 @@
-/*
- * Licensed 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 com.facebook.presto.operator.aggregation.minmaxby;
-
-import com.facebook.presto.spi.block.Block;
-import com.facebook.presto.spi.block.BlockBuilder;
-import com.facebook.presto.spi.type.Type;
-
-class UnknownAndBlockPositionStateSerializer
-        extends KeyAndBlockPositionValueStateSerializer<KeyAndBlockPositionValueState>
-{
-    UnknownAndBlockPositionStateSerializer(Type firstType, Type secondType)
-    {
-        super(firstType, secondType);
-    }
-
-    @Override
-    void readFirstField(Block block, int position, KeyAndBlockPositionValueState state)
-    {
-        throw new UnsupportedOperationException("UnknownAndBlockPositionStateSerializer does not support readFirstField");
-    }
-
-    @Override
-    void writeFirstField(BlockBuilder out, KeyAndBlockPositionValueState state)
-    {
-        throw new UnsupportedOperationException("UnknownAndBlockPositionStateSerializer does not support writeFirstField");
-    }
-}
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/UnknownBooleanState.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/UnknownBooleanState.java
deleted file mode 100644
index 0c303e4959da..000000000000
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/UnknownBooleanState.java
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Licensed 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 com.facebook.presto.operator.aggregation.minmaxby;
-
-public interface UnknownBooleanState
-        extends TwoNullableValueState
-{
-    // First state is void and will always be null
-
-    boolean getSecond();
-
-    void setSecond(boolean second);
-}
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/UnknownDoubleState.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/UnknownDoubleState.java
deleted file mode 100644
index e20a0d253e72..000000000000
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/UnknownDoubleState.java
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Licensed 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 com.facebook.presto.operator.aggregation.minmaxby;
-
-public interface UnknownDoubleState
-        extends TwoNullableValueState
-{
-    // First state is void and will always be null
-
-    double getSecond();
-
-    void setSecond(double second);
-}
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/UnknownLongState.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/UnknownLongState.java
deleted file mode 100644
index 0e18dbbc081f..000000000000
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/minmaxby/UnknownLongState.java
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Licensed 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 com.facebook.presto.operator.aggregation.minmaxby;
-
-public interface UnknownLongState
-        extends TwoNullableValueState
-{
-    // First state is void and will always be null
-
-    long getSecond();
-
-    void setSecond(long second);
-}
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayConstructor.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayConstructor.java
index 97e2d4c19a2f..067e5829d640 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayConstructor.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayConstructor.java
@@ -167,17 +167,12 @@ private static Class<?> generateArrayConstructor(List<Class<?>> stackTypes, Type
         body.append(createBlockBuilder);
 
         for (int i = 0; i < stackTypes.size(); i++) {
-            if (elementType.getJavaType() == void.class) {
-                body.append(blockBuilderVariable.invoke("appendNull", BlockBuilder.class));
-            }
-            else {
-                Variable argument = scope.getVariable("arg" + i);
-                IfStatement ifStatement = new IfStatement()
-                        .condition(equal(argument, constantNull(stackTypes.get(i))))
-                        .ifTrue(blockBuilderVariable.invoke("appendNull", BlockBuilder.class).pop())
-                        .ifFalse(constantType(binder, elementType).writeValue(blockBuilderVariable, argument.cast(elementType.getJavaType())));
-                body.append(ifStatement);
-            }
+            Variable argument = scope.getVariable("arg" + i);
+            IfStatement ifStatement = new IfStatement()
+                    .condition(equal(argument, constantNull(stackTypes.get(i))))
+                    .ifTrue(blockBuilderVariable.invoke("appendNull", BlockBuilder.class).pop())
+                    .ifFalse(constantType(binder, elementType).writeValue(blockBuilderVariable, argument.cast(elementType.getJavaType())));
+            body.append(ifStatement);
         }
 
         body.append(blockBuilderVariable.invoke("build", Block.class).ret());
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayContains.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayContains.java
index 28df3028d9ff..6fb0062334e0 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayContains.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayContains.java
@@ -35,13 +35,6 @@ public final class ArrayContains
 {
     private ArrayContains() {}
 
-    @SqlType(StandardTypes.BOOLEAN)
-    @SqlNullable
-    public static Boolean arrayWithUnknownType(@SqlType("array(unknown)") Block arrayBlock, @SqlNullable @SqlType("unknown") Void value)
-    {
-        return null;
-    }
-
     @TypeParameter("T")
     @SqlType(StandardTypes.BOOLEAN)
     @SqlNullable
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayElementAtFunction.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayElementAtFunction.java
index dabc7b82dd92..55274614e45c 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayElementAtFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayElementAtFunction.java
@@ -32,15 +32,6 @@ public final class ArrayElementAtFunction
 {
     private ArrayElementAtFunction() {}
 
-    @TypeParameter("E")
-    @SqlNullable
-    @SqlType("E")
-    public static Void voidElementAt(@SqlType("array(E)") Block array, @SqlType("bigint") long index)
-    {
-        checkedIndexToBlockPosition(array, index);
-        return null;
-    }
-
     @TypeParameter("E")
     @SqlNullable
     @SqlType("E")
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayFilterFunction.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayFilterFunction.java
index 3af0bdf92cc6..e2507d9cd0e9 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayFilterFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayFilterFunction.java
@@ -152,25 +152,6 @@ public static Block filterBlock(
         return resultBuilder.build();
     }
 
-    @TypeParameter("T")
-    @TypeParameterSpecialization(name = "T", nativeContainerType = void.class)
-    @SqlType("array(T)")
-    public static Block filterVoid(
-            @TypeParameter("T") Type elementType,
-            @SqlType("array(T)") Block arrayBlock,
-            @SqlType("function(T, boolean)") FilterVoidLambda function)
-    {
-        int positionCount = arrayBlock.getPositionCount();
-        BlockBuilder resultBuilder = elementType.createBlockBuilder(null, positionCount);
-        for (int position = 0; position < positionCount; position++) {
-            Boolean keep = function.apply(null);
-            if (TRUE.equals(keep)) {
-                resultBuilder.appendNull();
-            }
-        }
-        return resultBuilder.build();
-    }
-
     @FunctionalInterface
     public interface FilterLongLambda
             extends LambdaFunctionInterface
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayMaxFunction.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayMaxFunction.java
index 14018ad53acf..5dff5eb634ca 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayMaxFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayMaxFunction.java
@@ -39,16 +39,6 @@ public final class ArrayMaxFunction
 {
     private ArrayMaxFunction() {}
 
-    @TypeParameter("T")
-    @SqlType("T")
-    @SqlNullable
-    public static Void arrayWithUnknownType(
-            @OperatorDependency(operator = GREATER_THAN, returnType = StandardTypes.BOOLEAN, argumentTypes = {"T", "T"}) MethodHandle compareMethodHandle,
-            @SqlType("array(T)") Block block)
-    {
-        return null;
-    }
-
     @TypeParameter("T")
     @SqlType("T")
     @SqlNullable
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayMinFunction.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayMinFunction.java
index f606d640c3f9..e3bb12be369c 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayMinFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayMinFunction.java
@@ -39,16 +39,6 @@ public final class ArrayMinFunction
 {
     private ArrayMinFunction() {}
 
-    @TypeParameter("T")
-    @SqlType("T")
-    @SqlNullable
-    public static Void arrayWithUnknownType(
-            @OperatorDependency(operator = LESS_THAN, returnType = StandardTypes.BOOLEAN, argumentTypes = {"T", "T"}) MethodHandle compareMethodHandle,
-            @SqlType("array(T)") Block block)
-    {
-        return null;
-    }
-
     @TypeParameter("T")
     @SqlType("T")
     @SqlNullable
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayPositionFunction.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayPositionFunction.java
index 38b4fba2e170..94fa7f955589 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayPositionFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArrayPositionFunction.java
@@ -17,7 +17,6 @@
 import com.facebook.presto.spi.function.Description;
 import com.facebook.presto.spi.function.OperatorDependency;
 import com.facebook.presto.spi.function.ScalarFunction;
-import com.facebook.presto.spi.function.SqlNullable;
 import com.facebook.presto.spi.function.SqlType;
 import com.facebook.presto.spi.function.TypeParameter;
 import com.facebook.presto.spi.type.StandardTypes;
@@ -159,11 +158,4 @@ public static long arrayPosition(
         }
         return 0;
     }
-
-    @SqlType(StandardTypes.BIGINT)
-    @SqlNullable
-    public static Long arrayPosition(@SqlType("array(unknown)") Block array, @SqlNullable @SqlType("unknown") Void element)
-    {
-        return null;
-    }
 }
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArraySubscriptOperator.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArraySubscriptOperator.java
index c4c68b12ec98..8de352cadb8c 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArraySubscriptOperator.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/ArraySubscriptOperator.java
@@ -42,7 +42,6 @@ public class ArraySubscriptOperator
 {
     public static final ArraySubscriptOperator ARRAY_SUBSCRIPT = new ArraySubscriptOperator();
 
-    private static final MethodHandle METHOD_HANDLE_UNKNOWN = methodHandle(ArraySubscriptOperator.class, "arrayWithUnknownType", Type.class, Block.class, long.class);
     private static final MethodHandle METHOD_HANDLE_BOOLEAN = methodHandle(ArraySubscriptOperator.class, "booleanSubscript", Type.class, Block.class, long.class);
     private static final MethodHandle METHOD_HANDLE_LONG = methodHandle(ArraySubscriptOperator.class, "longSubscript", Type.class, Block.class, long.class);
     private static final MethodHandle METHOD_HANDLE_DOUBLE = methodHandle(ArraySubscriptOperator.class, "doubleSubscript", Type.class, Block.class, long.class);
@@ -65,10 +64,7 @@ public ScalarFunctionImplementation specialize(BoundVariables boundVariables, in
         Type elementType = boundVariables.getTypeVariable("E");
 
         MethodHandle methodHandle;
-        if (elementType.getJavaType() == void.class) {
-            methodHandle = METHOD_HANDLE_UNKNOWN;
-        }
-        else if (elementType.getJavaType() == boolean.class) {
+        if (elementType.getJavaType() == boolean.class) {
             methodHandle = METHOD_HANDLE_BOOLEAN;
         }
         else if (elementType.getJavaType() == long.class) {
@@ -94,12 +90,6 @@ else if (elementType.getJavaType() == Slice.class) {
                 isDeterministic());
     }
 
-    @UsedByGeneratedCode
-    public static void arrayWithUnknownType(Type elementType, Block array, long index)
-    {
-        checkIndex(array, index);
-    }
-
     @UsedByGeneratedCode
     public static Long longSubscript(Type elementType, Block array, long index)
     {
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/CastFromUnknownOperator.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/CastFromUnknownOperator.java
index fee26165b60a..fe9362e317c3 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/CastFromUnknownOperator.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/CastFromUnknownOperator.java
@@ -20,13 +20,12 @@
 import com.facebook.presto.spi.type.Type;
 import com.facebook.presto.spi.type.TypeManager;
 import com.google.common.collect.ImmutableList;
-import io.airlift.slice.Slice;
 
 import java.lang.invoke.MethodHandle;
 
 import static com.facebook.presto.metadata.Signature.typeVariable;
 import static com.facebook.presto.operator.scalar.ScalarFunctionImplementation.ArgumentProperty.valueTypeArgumentProperty;
-import static com.facebook.presto.operator.scalar.ScalarFunctionImplementation.NullConvention.USE_BOXED_TYPE;
+import static com.facebook.presto.operator.scalar.ScalarFunctionImplementation.NullConvention.RETURN_NULL_ON_NULL;
 import static com.facebook.presto.spi.function.OperatorType.CAST;
 import static com.facebook.presto.spi.type.TypeSignature.parseTypeSignature;
 import static com.facebook.presto.util.Reflection.methodHandle;
@@ -35,11 +34,7 @@ public final class CastFromUnknownOperator
         extends SqlOperator
 {
     public static final CastFromUnknownOperator CAST_FROM_UNKNOWN = new CastFromUnknownOperator();
-    private static final MethodHandle METHOD_HANDLE_LONG = methodHandle(CastFromUnknownOperator.class, "toLong", Void.class);
-    private static final MethodHandle METHOD_HANDLE_DOUBLE = methodHandle(CastFromUnknownOperator.class, "toDouble", Void.class);
-    private static final MethodHandle METHOD_HANDLE_BOOLEAN = methodHandle(CastFromUnknownOperator.class, "toBoolean", Void.class);
-    private static final MethodHandle METHOD_HANDLE_SLICE = methodHandle(CastFromUnknownOperator.class, "toSlice", Void.class);
-    private static final MethodHandle METHOD_HANDLE_OBJECT = methodHandle(CastFromUnknownOperator.class, "toObject", Void.class);
+    private static final MethodHandle METHOD_HANDLE_NON_NULL = methodHandle(CastFromUnknownOperator.class, "handleNonNull", boolean.class);
 
     public CastFromUnknownOperator()
     {
@@ -56,56 +51,17 @@ public ScalarFunctionImplementation specialize(
             FunctionRegistry functionRegistry)
     {
         Type toType = boundVariables.getTypeVariable("E");
-        MethodHandle methodHandle;
-        if (toType.getJavaType() == long.class) {
-            methodHandle = METHOD_HANDLE_LONG;
-        }
-        else if (toType.getJavaType() == double.class) {
-            methodHandle = METHOD_HANDLE_DOUBLE;
-        }
-        else if (toType.getJavaType() == boolean.class) {
-            methodHandle = METHOD_HANDLE_BOOLEAN;
-        }
-        else if (toType.getJavaType() == Slice.class) {
-            methodHandle = METHOD_HANDLE_SLICE;
-        }
-        else {
-            methodHandle = METHOD_HANDLE_OBJECT.asType(METHOD_HANDLE_OBJECT.type().changeReturnType(toType.getJavaType()));
-        }
+        MethodHandle methodHandle = METHOD_HANDLE_NON_NULL.asType(METHOD_HANDLE_NON_NULL.type().changeReturnType(toType.getJavaType()));
         return new ScalarFunctionImplementation(
-                true,
-                ImmutableList.of(valueTypeArgumentProperty(USE_BOXED_TYPE)),
+                false,
+                ImmutableList.of(valueTypeArgumentProperty(RETURN_NULL_ON_NULL)),
                 methodHandle,
                 isDeterministic());
     }
 
     @UsedByGeneratedCode
-    public static Long toLong(Void arg)
+    public static Object handleNonNull(boolean arg)
     {
-        return null;
-    }
-
-    @UsedByGeneratedCode
-    public static Double toDouble(Void arg)
-    {
-        return null;
-    }
-
-    @UsedByGeneratedCode
-    public static Boolean toBoolean(Void arg)
-    {
-        return null;
-    }
-
-    @UsedByGeneratedCode
-    public static Slice toSlice(Void arg)
-    {
-        return null;
-    }
-
-    @UsedByGeneratedCode
-    public static Object toObject(Void arg)
-    {
-        return null;
+        throw new IllegalArgumentException("value of unknown type should always be null");
     }
 }
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/FailureFunction.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/FailureFunction.java
index 238800285000..4d84e45a346b 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/FailureFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/FailureFunction.java
@@ -33,7 +33,7 @@ private FailureFunction() {}
     @Description("Decodes json to an exception and throws it")
     @ScalarFunction(value = "fail", hidden = true)
     @SqlType("unknown")
-    public static void failWithException(@SqlType(StandardTypes.JSON) Slice failureInfoSlice)
+    public static boolean failWithException(@SqlType(StandardTypes.JSON) Slice failureInfoSlice)
     {
         FailureInfo failureInfo = JSON_CODEC.fromJson(failureInfoSlice.getBytes());
         // wrap the failure in a new exception to append the current stack trace
@@ -43,7 +43,7 @@ public static void failWithException(@SqlType(StandardTypes.JSON) Slice failureI
     @Description("Throws an exception with a given message")
     @ScalarFunction(value = "fail", hidden = true)
     @SqlType("unknown")
-    public static void fail(@SqlType(StandardTypes.VARCHAR) Slice message)
+    public static boolean fail(@SqlType(StandardTypes.VARCHAR) Slice message)
     {
         throw new PrestoException(StandardErrorCode.GENERIC_USER_ERROR, message.toStringUtf8());
     }
@@ -51,7 +51,7 @@ public static void fail(@SqlType(StandardTypes.VARCHAR) Slice message)
     @Description("Throws an exception with a given error code and message")
     @ScalarFunction(value = "fail", hidden = true)
     @SqlType("unknown")
-    public static void fail(
+    public static boolean fail(
             @SqlType(StandardTypes.INTEGER) long errorCode,
             @SqlType(StandardTypes.VARCHAR) Slice message)
     {
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/MapElementAtFunction.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/MapElementAtFunction.java
index cd0d410f2796..31c69be6cbc9 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/MapElementAtFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/MapElementAtFunction.java
@@ -105,14 +105,7 @@ else if (keyType.getJavaType() == Slice.class) {
             methodHandle = METHOD_HANDLE_OBJECT;
         }
         methodHandle = methodHandle.bindTo(keyEqualsMethod).bindTo(keyType).bindTo(valueType);
-
-        // this casting is necessary because otherwise presto byte code generator will generate illegal byte code
-        if (valueType.getJavaType() == void.class) {
-            methodHandle = methodHandle.asType(methodHandle.type().changeReturnType(void.class));
-        }
-        else {
-            methodHandle = methodHandle.asType(methodHandle.type().changeReturnType(Primitives.wrap(valueType.getJavaType())));
-        }
+        methodHandle = methodHandle.asType(methodHandle.type().changeReturnType(Primitives.wrap(valueType.getJavaType())));
 
         return new ScalarFunctionImplementation(
                 true,
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/MapSubscriptOperator.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/MapSubscriptOperator.java
index 34d4af76fc50..2edf06a94efb 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/MapSubscriptOperator.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/MapSubscriptOperator.java
@@ -89,14 +89,7 @@ else if (keyType.getJavaType() == Slice.class) {
         methodHandle = MethodHandles.insertArguments(methodHandle, 0, legacyMissingKey);
         FunctionInvoker functionInvoker = new FunctionInvoker(functionRegistry);
         methodHandle = methodHandle.bindTo(functionInvoker).bindTo(keyType).bindTo(valueType);
-
-        // this casting is necessary because otherwise presto byte code generator will generate illegal byte code
-        if (valueType.getJavaType() == void.class) {
-            methodHandle = methodHandle.asType(methodHandle.type().changeReturnType(void.class));
-        }
-        else {
-            methodHandle = methodHandle.asType(methodHandle.type().changeReturnType(Primitives.wrap(valueType.getJavaType())));
-        }
+        methodHandle = methodHandle.asType(methodHandle.type().changeReturnType(Primitives.wrap(valueType.getJavaType())));
 
         return new ScalarFunctionImplementation(
                 true,
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/RepeatFunction.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/RepeatFunction.java
index 22d9222dd12e..5dc6272cad83 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/RepeatFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/RepeatFunction.java
@@ -40,7 +40,7 @@ private RepeatFunction() {}
 
     @SqlType("array(unknown)")
     public static Block repeat(
-            @SqlNullable @SqlType("unknown") Void element,
+            @SqlNullable @SqlType("unknown") Boolean element,
             @SqlType(StandardTypes.INTEGER) long count)
     {
         checkCondition(element == null, INVALID_FUNCTION_ARGUMENT, "expect null values");
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/TryCastFunction.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/TryCastFunction.java
index 840fb418c758..4b18339fa093 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/TryCastFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/TryCastFunction.java
@@ -28,10 +28,7 @@
 import java.util.List;
 
 import static com.facebook.presto.metadata.Signature.typeVariable;
-import static com.facebook.presto.operator.scalar.ScalarFunctionImplementation.ArgumentProperty.valueTypeArgumentProperty;
-import static com.facebook.presto.operator.scalar.ScalarFunctionImplementation.NullConvention.USE_BOXED_TYPE;
 import static com.facebook.presto.spi.type.TypeSignature.parseTypeSignature;
-import static com.facebook.presto.type.UnknownType.UNKNOWN;
 import static java.lang.invoke.MethodHandles.catchException;
 import static java.lang.invoke.MethodHandles.constant;
 import static java.lang.invoke.MethodHandles.dropArguments;
@@ -82,21 +79,15 @@ public ScalarFunctionImplementation specialize(BoundVariables boundVariables, in
         List<ArgumentProperty> argumentProperties;
         MethodHandle tryCastHandle;
 
-        if (fromType.equals(UNKNOWN)) {
-            argumentProperties = ImmutableList.of(valueTypeArgumentProperty(USE_BOXED_TYPE));
-            tryCastHandle = dropArguments(constant(returnType, null), 0, Void.class);
-        }
-        else {
-            // the resulting method needs to return a boxed type
-            Signature signature = functionRegistry.getCoercion(fromType, toType);
-            ScalarFunctionImplementation implementation = functionRegistry.getScalarFunctionImplementation(signature);
-            argumentProperties = ImmutableList.of(implementation.getArgumentProperty(0));
-            MethodHandle coercion = implementation.getMethodHandle();
-            coercion = coercion.asType(methodType(returnType, coercion.type()));
+        // the resulting method needs to return a boxed type
+        Signature signature = functionRegistry.getCoercion(fromType, toType);
+        ScalarFunctionImplementation implementation = functionRegistry.getScalarFunctionImplementation(signature);
+        argumentProperties = ImmutableList.of(implementation.getArgumentProperty(0));
+        MethodHandle coercion = implementation.getMethodHandle();
+        coercion = coercion.asType(methodType(returnType, coercion.type()));
 
-            MethodHandle exceptionHandler = dropArguments(constant(returnType, null), 0, RuntimeException.class);
-            tryCastHandle = catchException(coercion, RuntimeException.class, exceptionHandler);
-        }
+        MethodHandle exceptionHandler = dropArguments(constant(returnType, null), 0, RuntimeException.class);
+        tryCastHandle = catchException(coercion, RuntimeException.class, exceptionHandler);
 
         return new ScalarFunctionImplementation(true, argumentProperties, tryCastHandle, isDeterministic());
     }
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/TryFunction.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/TryFunction.java
index aa632870f46a..87df5165ce67 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/TryFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/TryFunction.java
@@ -110,21 +110,6 @@ public static Block tryBlock(@SqlType("function(T)") TryBlockLambda function)
         }
     }
 
-    @TypeParameter("T")
-    @TypeParameterSpecialization(name = "T", nativeContainerType = void.class)
-    @SqlNullable
-    @SqlType("T")
-    public static Void tryVoid(@SqlType("function(T)") TryVoidLambda function)
-    {
-        try {
-            return function.apply();
-        }
-        catch (PrestoException e) {
-            propagateIfUnhandled(e);
-            return null;
-        }
-    }
-
     @FunctionalInterface
     public interface TryLongLambda
             extends LambdaFunctionInterface
@@ -160,13 +145,6 @@ public interface TryBlockLambda
         Block apply();
     }
 
-    @FunctionalInterface
-    public interface TryVoidLambda
-            extends LambdaFunctionInterface
-    {
-        Void apply();
-    }
-
     private static void propagateIfUnhandled(PrestoException e)
             throws PrestoException
     {
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/scalar/TypeOfFunction.java b/presto-main/src/main/java/com/facebook/presto/operator/scalar/TypeOfFunction.java
index b0549199ccfb..323cacbe607f 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/scalar/TypeOfFunction.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/scalar/TypeOfFunction.java
@@ -65,13 +65,4 @@ public static Slice typeof(
     {
         return typeof(type, (Object) value);
     }
-
-    @TypeParameter("T")
-    @SqlType(StandardTypes.VARCHAR)
-    public static Slice typeof(
-            @TypeParameter("T") Type type,
-            @SqlNullable @SqlType("T") Void value)
-    {
-        return typeof(type, (Object) value);
-    }
 }
diff --git a/presto-main/src/main/java/com/facebook/presto/sql/gen/BytecodeUtils.java b/presto-main/src/main/java/com/facebook/presto/sql/gen/BytecodeUtils.java
index ffd6a28a26e3..decbdad5d144 100644
--- a/presto-main/src/main/java/com/facebook/presto/sql/gen/BytecodeUtils.java
+++ b/presto-main/src/main/java/com/facebook/presto/sql/gen/BytecodeUtils.java
@@ -41,7 +41,6 @@
 import java.util.List;
 import java.util.Optional;
 
-import static com.facebook.presto.operator.scalar.ScalarFunctionImplementation.ArgumentType.FUNCTION_TYPE;
 import static com.facebook.presto.operator.scalar.ScalarFunctionImplementation.ArgumentType.VALUE_TYPE;
 import static com.facebook.presto.sql.gen.Bootstrap.BOOTSTRAP_METHOD;
 import static com.google.common.base.Preconditions.checkArgument;
@@ -98,9 +97,7 @@ public static BytecodeNode handleNullValue(Scope scope,
 
         isNull.pushJavaDefault(returnType);
         String loadDefaultComment = null;
-        if (returnType != void.class) {
-            loadDefaultComment = format("loadJavaDefault(%s)", returnType.getName());
-        }
+        loadDefaultComment = format("loadJavaDefault(%s)", returnType.getName());
 
         isNull.gotoLabel(label);
 
@@ -230,9 +227,6 @@ else if (type == ConnectorSession.class) {
                                 block.append(ifWasNullPopAndGoto(scope, end, unboxedReturnType, Lists.reverse(stackTypes)));
                                 break;
                             case USE_NULL_FLAG:
-                                if (type == Void.class) {
-                                    block.append(boxPrimitiveIfNecessary(scope, type));
-                                }
                                 block.append(arguments.get(realParameterIndex));
                                 block.append(scope.getVariable("wasNull"));
                                 block.append(scope.getVariable("wasNull").set(constantFalse()));
@@ -281,11 +275,7 @@ public static BytecodeBlock unboxPrimitiveIfNecessary(Scope scope, Class<?> boxe
         Class<?> unboxedType = Primitives.unwrap(boxedType);
         Variable wasNull = scope.getVariable("wasNull");
 
-        if (unboxedType == void.class) {
-            block.pop(boxedType)
-                    .append(wasNull.set(constantTrue()));
-        }
-        else if (unboxedType.isPrimitive()) {
+        if (unboxedType.isPrimitive()) {
             LabelNode notNull = new LabelNode("notNull");
             block.dup(boxedType)
                     .ifNotNullGoto(notNull)
@@ -327,11 +317,6 @@ else if (type == Boolean.class) {
             notNull.invokeStatic(Boolean.class, "valueOf", Boolean.class, boolean.class);
             expectedCurrentStackType = boolean.class;
         }
-        else if (type == Void.class) {
-            notNull.pushNull()
-                    .checkCast(Void.class);
-            return notNull;
-        }
         else {
             throw new UnsupportedOperationException("not yet implemented: " + type);
         }
@@ -361,12 +346,6 @@ public static BytecodeExpression invoke(Binding binding, Signature signature)
 
     public static BytecodeNode generateWrite(CallSiteBinder callSiteBinder, Scope scope, Variable wasNullVariable, Type type)
     {
-        if (type.getJavaType() == void.class) {
-            return new BytecodeBlock().comment("output.appendNull();")
-                    .invokeInterface(BlockBuilder.class, "appendNull", BlockBuilder.class)
-                    .pop();
-        }
-
         Class<?> valueJavaType = type.getJavaType();
         if (!valueJavaType.isPrimitive() && valueJavaType != Slice.class) {
             valueJavaType = Object.class;
diff --git a/presto-main/src/main/java/com/facebook/presto/sql/gen/NullIfCodeGenerator.java b/presto-main/src/main/java/com/facebook/presto/sql/gen/NullIfCodeGenerator.java
index fb27917c6a58..885b71a204c8 100644
--- a/presto-main/src/main/java/com/facebook/presto/sql/gen/NullIfCodeGenerator.java
+++ b/presto-main/src/main/java/com/facebook/presto/sql/gen/NullIfCodeGenerator.java
@@ -43,12 +43,6 @@ public BytecodeNode generateExpression(Signature signature, BytecodeGeneratorCon
         RowExpression first = arguments.get(0);
         RowExpression second = arguments.get(1);
 
-        if (first.getType().getJavaType() == void.class) {
-            return new BytecodeBlock()
-                            .comment("NULLIF(NULL, *) = NULL")
-                            .append(generatorContext.generate(first));
-        }
-
         LabelNode notMatch = new LabelNode("notMatch");
 
         // push first arg on the stack
diff --git a/presto-main/src/main/java/com/facebook/presto/sql/gen/RowConstructorCodeGenerator.java b/presto-main/src/main/java/com/facebook/presto/sql/gen/RowConstructorCodeGenerator.java
index 4ad0dcd4834e..1ed85d55734b 100644
--- a/presto-main/src/main/java/com/facebook/presto/sql/gen/RowConstructorCodeGenerator.java
+++ b/presto-main/src/main/java/com/facebook/presto/sql/gen/RowConstructorCodeGenerator.java
@@ -56,22 +56,15 @@ public BytecodeNode generateExpression(Signature signature, BytecodeGeneratorCon
 
         for (int i = 0; i < arguments.size(); ++i) {
             Type fieldType = types.get(i);
-            Class<?> javaType = fieldType.getJavaType();
-            if (javaType == void.class) {
-                block.comment(i + "-th field type of row is undefined");
-                block.append(singleRowBlockWriter.invoke("appendNull", BlockBuilder.class).pop());
-            }
-            else {
-                Variable field = scope.createTempVariable(javaType);
-                block.comment("Clean wasNull and Generate + " + i + "-th field of row");
-                block.append(context.wasNull().set(constantFalse()));
-                block.append(context.generate(arguments.get(i)));
-                block.putVariable(field);
-                block.append(new IfStatement()
-                        .condition(context.wasNull())
-                        .ifTrue(singleRowBlockWriter.invoke("appendNull", BlockBuilder.class).pop())
-                        .ifFalse(constantType(binder, fieldType).writeValue(singleRowBlockWriter, field).pop()));
-            }
+            Variable field = scope.createTempVariable(fieldType.getJavaType());
+            block.comment("Clean wasNull and Generate + " + i + "-th field of row");
+            block.append(context.wasNull().set(constantFalse()));
+            block.append(context.generate(arguments.get(i)));
+            block.putVariable(field);
+            block.append(new IfStatement()
+                    .condition(context.wasNull())
+                    .ifTrue(singleRowBlockWriter.invoke("appendNull", BlockBuilder.class).pop())
+                    .ifFalse(constantType(binder, fieldType).writeValue(singleRowBlockWriter, field).pop()));
         }
         block.comment("closeEntry; slice the SingleRowBlock; wasNull = false;");
         block.append(blockBuilder.invoke("closeEntry", BlockBuilder.class).pop());
diff --git a/presto-main/src/main/java/com/facebook/presto/sql/gen/RowExpressionCompiler.java b/presto-main/src/main/java/com/facebook/presto/sql/gen/RowExpressionCompiler.java
index ea3a4cfaf361..bd01331648dd 100644
--- a/presto-main/src/main/java/com/facebook/presto/sql/gen/RowExpressionCompiler.java
+++ b/presto-main/src/main/java/com/facebook/presto/sql/gen/RowExpressionCompiler.java
@@ -183,9 +183,6 @@ public BytecodeNode visitConstant(ConstantExpression constant, Context context)
             if (javaType == String.class) {
                 return block.append(loadString((String) value));
             }
-            if (javaType == void.class) {
-                return block;
-            }
 
             // bind constant object directly into the call-site using invoke dynamic
             Binding binding = callSiteBinder.bind(value, constant.getType().getJavaType());
diff --git a/presto-main/src/main/java/com/facebook/presto/type/UnknownOperators.java b/presto-main/src/main/java/com/facebook/presto/type/UnknownOperators.java
index 94744e3abf90..32241a65ad96 100644
--- a/presto-main/src/main/java/com/facebook/presto/type/UnknownOperators.java
+++ b/presto-main/src/main/java/com/facebook/presto/type/UnknownOperators.java
@@ -37,75 +37,67 @@ private UnknownOperators()
     }
 
     @ScalarOperator(EQUAL)
-    @SqlNullable
     @SqlType(StandardTypes.BOOLEAN)
-    public static Boolean equal(@SqlType("unknown") @SqlNullable Void left, @SqlType("unknown") @SqlNullable Void right)
+    public static boolean equal(@SqlType("unknown") boolean left, @SqlType("unknown") boolean right)
     {
-        return null;
+        throw new AssertionError("value of unknown type should all be NULL");
     }
 
     @ScalarOperator(NOT_EQUAL)
-    @SqlNullable
     @SqlType(StandardTypes.BOOLEAN)
-    public static Boolean notEqual(@SqlType("unknown") @SqlNullable Void left, @SqlType("unknown") @SqlNullable Void right)
+    public static boolean notEqual(@SqlType("unknown") boolean left, @SqlType("unknown") boolean right)
     {
-        return null;
+        throw new AssertionError("value of unknown type should all be NULL");
     }
 
     @ScalarOperator(LESS_THAN)
-    @SqlNullable
     @SqlType(StandardTypes.BOOLEAN)
-    public static Boolean lessThan(@SqlType("unknown") @SqlNullable Void left, @SqlType("unknown") @SqlNullable Void right)
+    public static boolean lessThan(@SqlType("unknown") boolean left, @SqlType("unknown") boolean right)
     {
-        return null;
+        throw new AssertionError("value of unknown type should all be NULL");
     }
 
     @ScalarOperator(LESS_THAN_OR_EQUAL)
-    @SqlNullable
     @SqlType(StandardTypes.BOOLEAN)
-    public static Boolean lessThanOrEqual(@SqlType("unknown") @SqlNullable Void left, @SqlType("unknown") @SqlNullable Void right)
+    public static boolean lessThanOrEqual(@SqlType("unknown") boolean left, @SqlType("unknown") boolean right)
     {
-        return null;
+        throw new AssertionError("value of unknown type should all be NULL");
     }
 
     @ScalarOperator(GREATER_THAN)
-    @SqlNullable
     @SqlType(StandardTypes.BOOLEAN)
-    public static Boolean greaterThan(@SqlType("unknown") @SqlNullable Void left, @SqlType("unknown") @SqlNullable Void right)
+    public static boolean greaterThan(@SqlType("unknown") boolean left, @SqlType("unknown") boolean right)
     {
-        return null;
+        throw new AssertionError("value of unknown type should all be NULL");
     }
 
     @ScalarOperator(GREATER_THAN_OR_EQUAL)
-    @SqlNullable
     @SqlType(StandardTypes.BOOLEAN)
-    public static Boolean greaterThanOrEqual(@SqlType("unknown") @SqlNullable Void left, @SqlType("unknown") @SqlNullable Void right)
+    public static boolean greaterThanOrEqual(@SqlType("unknown") boolean left, @SqlType("unknown") boolean right)
     {
-        return null;
+        throw new AssertionError("value of unknown type should all be NULL");
     }
 
     @ScalarOperator(BETWEEN)
-    @SqlNullable
     @SqlType(StandardTypes.BOOLEAN)
-    public static Boolean between(@SqlType("unknown") @SqlNullable Void value, @SqlType("unknown") @SqlNullable Void min, @SqlType("unknown") @SqlNullable Void max)
+    public static boolean between(@SqlType("unknown") boolean value, @SqlType("unknown") boolean min, @SqlType("unknown") boolean max)
     {
-        return null;
+        throw new AssertionError("value of unknown type should all be NULL");
     }
 
     @ScalarOperator(HASH_CODE)
-    @SqlNullable
     @SqlType(StandardTypes.BIGINT)
-    public static Long hashCode(@SqlType("unknown") @SqlNullable Void value)
+    public static long hashCode(@SqlType("unknown") boolean value)
     {
-        return null;
+        throw new AssertionError("value of unknown type should all be NULL");
     }
 
     @ScalarOperator(IS_DISTINCT_FROM)
     @SqlType(StandardTypes.BOOLEAN)
     public static boolean isDistinctFrom(
-            @SqlType("unknown") Void left,
+            @SqlType("unknown") boolean left,
             @IsNull boolean leftNull,
-            @SqlType("unknown") Void right,
+            @SqlType("unknown") boolean right,
             @IsNull boolean rightNull)
     {
         return false;
@@ -113,7 +105,7 @@ public static boolean isDistinctFrom(
 
     @ScalarOperator(INDETERMINATE)
     @SqlType(StandardTypes.BOOLEAN)
-    public static boolean indeterminate(@SqlType("unknown") @SqlNullable Void value)
+    public static boolean indeterminate(@SqlType("unknown") @SqlNullable Boolean value)
     {
         return true;
     }
diff --git a/presto-main/src/main/java/com/facebook/presto/type/UnknownType.java b/presto-main/src/main/java/com/facebook/presto/type/UnknownType.java
index 37329e4069d6..514bd38f9a04 100644
--- a/presto-main/src/main/java/com/facebook/presto/type/UnknownType.java
+++ b/presto-main/src/main/java/com/facebook/presto/type/UnknownType.java
@@ -29,7 +29,10 @@ public final class UnknownType
 
     private UnknownType()
     {
-        super(new TypeSignature(NAME), void.class, 0);
+        // We never access the native container for UNKNOWN because its null check is always true.
+        // The actual native container type does not matter here.
+        // We choose boolean to represent UNKNOWN because it's the smallest primitive type.
+        super(new TypeSignature(NAME), boolean.class, 1);
     }
 
     @Override
@@ -83,4 +86,13 @@ public void appendTo(Block block, int position, BlockBuilder blockBuilder)
     {
         blockBuilder.appendNull();
     }
+
+    @Override
+    public boolean getBoolean(Block block, int position)
+    {
+        // Ideally, this function should never be invoked for unknown type.
+        // However, some logic rely on having a default value before the null check.
+        checkArgument(block.isNull(position));
+        return false;
+    }
 }
diff --git a/presto-main/src/test/java/com/facebook/presto/operator/scalar/TestIsNullAnnotation.java b/presto-main/src/test/java/com/facebook/presto/operator/scalar/TestIsNullAnnotation.java
index e3ad98a8a338..833d45263c99 100644
--- a/presto-main/src/test/java/com/facebook/presto/operator/scalar/TestIsNullAnnotation.java
+++ b/presto-main/src/test/java/com/facebook/presto/operator/scalar/TestIsNullAnnotation.java
@@ -86,7 +86,7 @@ public static Slice testIsNull(
 
     @ScalarFunction("test_is_null_void")
     @SqlType(StandardTypes.BOOLEAN)
-    public static boolean testIsNullVoid(@SqlType("unknown") Void value, @IsNull boolean isNull)
+    public static boolean testIsNullVoid(@SqlType("unknown") boolean value, @IsNull boolean isNull)
     {
         return isNull;
     }
diff --git a/presto-main/src/test/java/com/facebook/presto/type/AbstractTestType.java b/presto-main/src/test/java/com/facebook/presto/type/AbstractTestType.java
index f2b5373bfed1..fe43321a1024 100644
--- a/presto-main/src/test/java/com/facebook/presto/type/AbstractTestType.java
+++ b/presto-main/src/test/java/com/facebook/presto/type/AbstractTestType.java
@@ -45,6 +45,7 @@
 import static com.facebook.presto.type.TypeUtils.positionEqualsPosition;
 import static com.facebook.presto.util.StructuralTestUtil.arrayBlockOf;
 import static com.facebook.presto.util.StructuralTestUtil.mapBlockOf;
+import static com.google.common.base.Preconditions.checkState;
 import static io.airlift.testing.Assertions.assertInstanceOf;
 import static java.util.Collections.unmodifiableSortedMap;
 import static java.util.Objects.requireNonNull;
@@ -84,7 +85,8 @@ private Block createAlternatingNullsBlock(Block testBlock)
     {
         BlockBuilder nullsBlockBuilder = type.createBlockBuilder(null, testBlock.getPositionCount());
         for (int position = 0; position < testBlock.getPositionCount(); position++) {
-            if (type.getJavaType() == void.class) {
+            if (testBlock.isNull(position)) {
+                checkState(type instanceof UnknownType);
                 nullsBlockBuilder.appendNull();
             }
             else if (type.getJavaType() == boolean.class) {
@@ -184,7 +186,7 @@ private void assertPositionValue(Block block, int position, Object expectedStack
         verifyInvalidPositionHandling(block);
 
         if (block.isNull(position)) {
-            if (type.isOrderable() && type.getJavaType() != void.class) {
+            if (type.isOrderable() && !(type instanceof UnknownType)) {
                 Block nonNullValue = toBlock(getNonNullValue());
                 assertTrue(ASC_NULLS_FIRST.compareBlockValue(type, block, position, nonNullValue, 0) < 0);
                 assertTrue(ASC_NULLS_LAST.compareBlockValue(type, block, position, nonNullValue, 0) > 0);
@@ -353,7 +355,7 @@ private void verifyInvalidPositionHandling(Block block)
         catch (RuntimeException expected) {
         }
 
-        if (type.isComparable() && type.getJavaType() != void.class) {
+        if (type.isComparable() && !(type instanceof UnknownType)) {
             Block other = toBlock(getNonNullValue());
             try {
                 type.equalTo(block, -1, other, 0);
@@ -369,7 +371,7 @@ private void verifyInvalidPositionHandling(Block block)
             }
         }
 
-        if (type.isOrderable() && type.getJavaType() != void.class) {
+        if (type.isOrderable() && !(type instanceof UnknownType)) {
             Block other = toBlock(getNonNullValue());
             try {
                 ASC_NULLS_FIRST.compareBlockValue(type, block, -1, other, 0);
diff --git a/presto-main/src/test/java/com/facebook/presto/type/TestUnknownOperators.java b/presto-main/src/test/java/com/facebook/presto/type/TestUnknownOperators.java
index 42ce40cb1524..84c78564eb7b 100644
--- a/presto-main/src/test/java/com/facebook/presto/type/TestUnknownOperators.java
+++ b/presto-main/src/test/java/com/facebook/presto/type/TestUnknownOperators.java
@@ -39,7 +39,7 @@ public void setUp()
     @ScalarFunction(value = "null_function", deterministic = false)
     @SqlNullable
     @SqlType("unknown")
-    public static Void nullFunction()
+    public static Boolean nullFunction()
     {
         return null;
     }
diff --git a/presto-main/src/test/java/com/facebook/presto/type/TestUnknownType.java b/presto-main/src/test/java/com/facebook/presto/type/TestUnknownType.java
index 623a8cd0fdb5..ba8c8a0667c2 100644
--- a/presto-main/src/test/java/com/facebook/presto/type/TestUnknownType.java
+++ b/presto-main/src/test/java/com/facebook/presto/type/TestUnknownType.java
@@ -21,7 +21,7 @@ public class TestUnknownType
     public TestUnknownType()
     {
         super(UNKNOWN,
-                void.class,
+                boolean.class,
                 UNKNOWN.createBlockBuilder(null, 3)
                         .appendNull()
                         .appendNull()
diff --git a/presto-spi/src/main/java/com/facebook/presto/spi/block/MethodHandleUtil.java b/presto-spi/src/main/java/com/facebook/presto/spi/block/MethodHandleUtil.java
index 8ba7b2659d51..2f97d52783b8 100644
--- a/presto-spi/src/main/java/com/facebook/presto/spi/block/MethodHandleUtil.java
+++ b/presto-spi/src/main/java/com/facebook/presto/spi/block/MethodHandleUtil.java
@@ -33,7 +33,6 @@ public final class MethodHandleUtil
     private static final MethodHandle GET_BOOLEAN = methodHandle(Type.class, "getBoolean", Block.class, int.class);
     private static final MethodHandle GET_SLICE = methodHandle(Type.class, "getSlice", Block.class, int.class);
     private static final MethodHandle GET_BLOCK = methodHandle(Type.class, "getObject", Block.class, int.class).asType(methodType(Block.class, Type.class, Block.class, int.class));
-    private static final MethodHandle GET_UNKNOWN = methodHandle(MethodHandleUtil.class, "unknownGetter", Type.class, Block.class, int.class);
 
     private static final MethodHandle WRITE_LONG = methodHandle(Type.class, "writeLong", BlockBuilder.class, long.class);
     private static final MethodHandle WRITE_DOUBLE = methodHandle(Type.class, "writeDouble", BlockBuilder.class, double.class);
@@ -146,9 +145,6 @@ else if (javaType == Slice.class) {
         else if (javaType == Block.class) {
             methodHandle = GET_BLOCK;
         }
-        else if (javaType == void.class) {
-            methodHandle = GET_UNKNOWN;
-        }
         else {
             throw new IllegalArgumentException("Unknown java type " + javaType + " from type " + type);
         }
@@ -182,9 +178,4 @@ else if (javaType == Block.class) {
 
         return methodHandle.bindTo(type);
     }
-
-    public static Void unknownGetter(Type type, Block block, int position)
-    {
-        throw new IllegalArgumentException("For UNKNOWN type, getter should never be invoked on Block");
-    }
 }
diff --git a/presto-spi/src/main/java/com/facebook/presto/spi/predicate/Primitives.java b/presto-spi/src/main/java/com/facebook/presto/spi/predicate/Primitives.java
index 031f99572881..074b19a1d2d4 100644
--- a/presto-spi/src/main/java/com/facebook/presto/spi/predicate/Primitives.java
+++ b/presto-spi/src/main/java/com/facebook/presto/spi/predicate/Primitives.java
@@ -58,7 +58,6 @@ private Primitives() {}
         add(primToWrap, wrapToPrim, int.class, Integer.class);
         add(primToWrap, wrapToPrim, long.class, Long.class);
         add(primToWrap, wrapToPrim, short.class, Short.class);
-        add(primToWrap, wrapToPrim, void.class, Void.class);
 
         PRIMITIVE_TO_WRAPPER_TYPE = Collections.unmodifiableMap(primToWrap);
         WRAPPER_TO_PRIMITIVE_TYPE = Collections.unmodifiableMap(wrapToPrim);
@@ -84,8 +83,7 @@ public static Set<Class<?>> allPrimitiveTypes()
     }
 
     /**
-     * Returns an immutable set of all nine primitive-wrapper types (including
-     * {@link Void}).
+     * Returns an immutable set of all eight primitive-wrapper types
      *
      * @since 3.0
      */