/*
* 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.scalar;
import com.facebook.presto.metadata.BoundVariables;
import com.facebook.presto.metadata.FunctionKind;
import com.facebook.presto.metadata.FunctionRegistry;
import com.facebook.presto.metadata.Signature;
import com.facebook.presto.metadata.SqlScalarFunction;
import com.facebook.presto.spi.type.Type;
import com.facebook.presto.spi.type.TypeManager;
import com.google.common.collect.ImmutableList;
import com.google.common.primitives.Primitives;
import java.lang.invoke.MethodHandle;
import java.util.List;
import static com.facebook.presto.metadata.Signature.typeVariable;
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;
import static java.lang.invoke.MethodType.methodType;
public class TryCastFunction
extends SqlScalarFunction
{
public static final TryCastFunction TRY_CAST = new TryCastFunction();
public TryCastFunction()
{
super(new Signature(
"TRY_CAST",
FunctionKind.SCALAR,
ImmutableList.of(typeVariable("F"), typeVariable("T")),
ImmutableList.of(),
parseTypeSignature("T"),
ImmutableList.of(parseTypeSignature("F")),
false));
}
@Override
public boolean isHidden()
{
return true;
}
@Override
public boolean isDeterministic()
{
return true;
}
@Override
public String getDescription()
{
return "";
}
@Override
public ScalarFunctionImplementation specialize(BoundVariables boundVariables, int arity, TypeManager typeManager, FunctionRegistry functionRegistry)
{
Type fromType = boundVariables.getTypeVariable("F");
Type toType = boundVariables.getTypeVariable("T");
Class<?> returnType = Primitives.wrap(toType.getJavaType());
List<Boolean> nullableArguments;
MethodHandle tryCastHandle;
if (fromType.equals(UNKNOWN)) {
nullableArguments = ImmutableList.of(true);
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);
nullableArguments = implementation.getNullableArguments();
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);
}
return new ScalarFunctionImplementation(true, nullableArguments, tryCastHandle, isDeterministic());
}
}