/*
* 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.ConnectorSession;
import com.facebook.presto.spi.type.Type;
import com.facebook.presto.spi.type.TypeManager;
import com.google.common.base.Throwables;
import com.google.common.collect.ImmutableList;
import java.lang.invoke.MethodHandle;
import static com.facebook.presto.metadata.Signature.typeVariable;
import static com.facebook.presto.spi.type.TypeSignature.parseTypeSignature;
import static com.facebook.presto.util.Reflection.methodHandle;
import static com.google.common.primitives.Primitives.wrap;
/**
* This scalar function exists primarily to test lambda expression support.
*/
public final class ApplyFunction
extends SqlScalarFunction
{
public static final ApplyFunction APPLY_FUNCTION = new ApplyFunction();
private static final MethodHandle METHOD_HANDLE = methodHandle(ApplyFunction.class, "apply", ConnectorSession.class, Object.class, MethodHandle.class);
private ApplyFunction()
{
super(new Signature(
"apply",
FunctionKind.SCALAR,
ImmutableList.of(typeVariable("T"), typeVariable("U")),
ImmutableList.of(),
parseTypeSignature("U"),
ImmutableList.of(parseTypeSignature("T"), parseTypeSignature("function(T,U)")),
false));
}
@Override
public boolean isHidden()
{
return true;
}
@Override
public boolean isDeterministic()
{
return true;
}
@Override
public String getDescription()
{
return "lambda apply function";
}
@Override
public ScalarFunctionImplementation specialize(BoundVariables boundVariables, int arity, TypeManager typeManager, FunctionRegistry functionRegistry)
{
Type argumentType = boundVariables.getTypeVariable("T");
Type returnType = boundVariables.getTypeVariable("U");
return new ScalarFunctionImplementation(
true,
ImmutableList.of(true, false),
METHOD_HANDLE.asType(
METHOD_HANDLE.type()
.changeReturnType(wrap(returnType.getJavaType()))
.changeParameterType(1, wrap(argumentType.getJavaType()))),
isDeterministic());
}
public static Object apply(ConnectorSession session, Object input, MethodHandle function)
{
try {
return function.invoke(session, input);
}
catch (Throwable throwable) {
throw Throwables.propagate(throwable);
}
}
}