/*
* 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.block.Block;
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 com.google.common.primitives.Primitives;
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.spi.type.TypeUtils.readNativeValue;
import static com.facebook.presto.util.Reflection.methodHandle;
public final class ArrayReduceFunction
extends SqlScalarFunction
{
public static final ArrayReduceFunction ARRAY_REDUCE_FUNCTION = new ArrayReduceFunction();
private static final MethodHandle METHOD_HANDLE = methodHandle(ArrayReduceFunction.class, "reduce", Type.class, ConnectorSession.class, Block.class, Object.class, MethodHandle.class, MethodHandle.class);
private ArrayReduceFunction()
{
super(new Signature(
"reduce",
FunctionKind.SCALAR,
ImmutableList.of(typeVariable("T"), typeVariable("S"), typeVariable("R")),
ImmutableList.of(),
parseTypeSignature("R"),
ImmutableList.of(parseTypeSignature("array(T)"), parseTypeSignature("S"), parseTypeSignature("function(S,T,S)"), parseTypeSignature("function(S,R)")),
false));
}
@Override
public boolean isHidden()
{
return false;
}
@Override
public boolean isDeterministic()
{
return false;
}
@Override
public String getDescription()
{
return "Reduce elements of the array into a single value";
}
@Override
public ScalarFunctionImplementation specialize(BoundVariables boundVariables, int arity, TypeManager typeManager, FunctionRegistry functionRegistry)
{
Type inputType = boundVariables.getTypeVariable("T");
Type intermediateType = boundVariables.getTypeVariable("S");
Type outputType = boundVariables.getTypeVariable("R");
MethodHandle methodHandle = METHOD_HANDLE.bindTo(inputType);
return new ScalarFunctionImplementation(
true,
ImmutableList.of(false, true, false, false),
methodHandle.asType(
methodHandle.type()
.changeParameterType(2, Primitives.wrap(intermediateType.getJavaType()))
.changeReturnType(Primitives.wrap(outputType.getJavaType()))),
isDeterministic());
}
public static Object reduce(
Type inputType,
ConnectorSession session,
Block block,
Object initialIntermediateValue,
MethodHandle inputFunction,
MethodHandle outputFunction)
{
int positionCount = block.getPositionCount();
Object intermediateValue = initialIntermediateValue;
for (int position = 0; position < positionCount; position++) {
Object input = readNativeValue(inputType, block, position);
try {
intermediateValue = inputFunction.invoke(session, intermediateValue, input);
}
catch (Throwable throwable) {
throw Throwables.propagate(throwable);
}
}
try {
return outputFunction.invoke(session, intermediateValue);
}
catch (Throwable throwable) {
throw Throwables.propagate(throwable);
}
}
}