/*
* 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.block.Block;
import com.facebook.presto.spi.block.BlockBuilder;
import com.facebook.presto.spi.block.BlockBuilderStatus;
import com.facebook.presto.spi.type.StandardTypes;
import com.facebook.presto.spi.type.Type;
import com.facebook.presto.spi.type.TypeManager;
import com.facebook.presto.spi.type.TypeSignatureParameter;
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;
public class ArrayFlattenFunction
extends SqlScalarFunction
{
public static final ArrayFlattenFunction ARRAY_FLATTEN_FUNCTION = new ArrayFlattenFunction();
private static final String FUNCTION_NAME = "flatten";
private static final MethodHandle METHOD_HANDLE = methodHandle(ArrayFlattenFunction.class, FUNCTION_NAME, Type.class, Type.class, Block.class);
private ArrayFlattenFunction()
{
super(new Signature(FUNCTION_NAME,
FunctionKind.SCALAR,
ImmutableList.of(typeVariable("E")),
ImmutableList.of(),
parseTypeSignature("array(E)"),
ImmutableList.of(parseTypeSignature("array(array(E))")),
false));
}
@Override
public boolean isHidden()
{
return false;
}
@Override
public boolean isDeterministic()
{
return true;
}
@Override
public String getDescription()
{
return "Flattens the given array";
}
@Override
public ScalarFunctionImplementation specialize(BoundVariables boundVariables, int arity, TypeManager typeManager, FunctionRegistry functionRegistry)
{
Type elementType = boundVariables.getTypeVariable("E");
Type arrayType = typeManager.getParameterizedType(StandardTypes.ARRAY, ImmutableList.of(TypeSignatureParameter.of(elementType.getTypeSignature())));
MethodHandle methodHandle = METHOD_HANDLE.bindTo(elementType).bindTo(arrayType);
return new ScalarFunctionImplementation(false, ImmutableList.of(false), methodHandle, isDeterministic());
}
public static Block flatten(Type type, Type arrayType, Block array)
{
if (array.getPositionCount() == 0) {
return type.createBlockBuilder(new BlockBuilderStatus(), 0).build();
}
BlockBuilder builder = type.createBlockBuilder(new BlockBuilderStatus(), array.getPositionCount(), array.getSizeInBytes() / array.getPositionCount());
for (int i = 0; i < array.getPositionCount(); i++) {
if (!array.isNull(i)) {
Block subArray = (Block) arrayType.getObject(array, i);
for (int j = 0; j < subArray.getPositionCount(); j++) {
type.appendTo(subArray, j, builder);
}
}
}
return builder.build();
}
}