/*
* 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.annotation.UsedByGeneratedCode;
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.Type;
import com.facebook.presto.spi.type.TypeManager;
import com.facebook.presto.spi.type.TypeSignature;
import com.facebook.presto.type.RowType;
import com.google.common.collect.ImmutableList;
import java.lang.invoke.MethodHandle;
import java.util.List;
import java.util.Optional;
import java.util.stream.IntStream;
import static com.facebook.presto.spi.type.TypeSignature.parseTypeSignature;
import static com.facebook.presto.util.Reflection.methodHandle;
import static com.google.common.collect.ImmutableList.toImmutableList;
import static java.lang.String.join;
import static java.lang.invoke.MethodType.methodType;
public final class ZipFunction
extends SqlScalarFunction
{
public static final int MIN_ARITY = 2;
public static final int MAX_ARITY = 4;
public static final ZipFunction[] ZIP_FUNCTIONS;
private static final MethodHandle METHOD_HANDLE = methodHandle(ZipFunction.class, "zip", List.class, Block[].class);
static
{
ZIP_FUNCTIONS = new ZipFunction[MAX_ARITY - MIN_ARITY + 1];
for (int arity = MIN_ARITY; arity <= MAX_ARITY; arity++) {
ZIP_FUNCTIONS[arity - MIN_ARITY] = new ZipFunction(arity);
}
}
private final List<String> typeParameters;
private ZipFunction(int arity)
{
this(IntStream.rangeClosed(1, arity).mapToObj(s -> "T" + s).collect(toImmutableList()));
}
private ZipFunction(List<String> typeParameters)
{
super(new Signature("zip",
FunctionKind.SCALAR,
typeParameters.stream().map(Signature::typeVariable).collect(toImmutableList()),
ImmutableList.of(),
parseTypeSignature("array(row(" + join(",", typeParameters) + "))"),
typeParameters.stream().map(name -> "array(" + name + ")").map(TypeSignature::parseTypeSignature).collect(toImmutableList()),
false));
this.typeParameters = typeParameters;
}
@Override
public boolean isHidden()
{
return false;
}
@Override
public boolean isDeterministic()
{
return true;
}
@Override
public String getDescription()
{
return "Merges the given arrays, element-wise, into a single array of rows.";
}
@Override
public ScalarFunctionImplementation specialize(BoundVariables boundVariables, int arity, TypeManager typeManager, FunctionRegistry functionRegistry)
{
List<Type> types = this.typeParameters.stream().map(boundVariables::getTypeVariable).collect(toImmutableList());
List<Boolean> nullableArguments = types.stream().map(type -> false).collect(toImmutableList());
List<Class<?>> javaArgumentTypes = types.stream().map(type -> Block.class).collect(toImmutableList());
MethodHandle methodHandle = METHOD_HANDLE.bindTo(types).asVarargsCollector(Block[].class).asType(methodType(Block.class, javaArgumentTypes));
return new ScalarFunctionImplementation(false, nullableArguments, methodHandle, isDeterministic());
}
@UsedByGeneratedCode
public static Block zip(List<Type> types, Block... arrays)
{
int biggestCardinality = 0;
for (Block array : arrays) {
biggestCardinality = Math.max(biggestCardinality, array.getPositionCount());
}
RowType rowType = new RowType(types, Optional.empty());
BlockBuilder outputBuilder = rowType.createBlockBuilder(new BlockBuilderStatus(), biggestCardinality);
for (int outputPosition = 0; outputPosition < biggestCardinality; outputPosition++) {
BlockBuilder rowBuilder = outputBuilder.beginBlockEntry();
for (int fieldIndex = 0; fieldIndex < arrays.length; fieldIndex++) {
if (arrays[fieldIndex].getPositionCount() <= outputPosition) {
rowBuilder.appendNull();
}
else {
types.get(fieldIndex).appendTo(arrays[fieldIndex], outputPosition, rowBuilder);
}
}
outputBuilder.closeEntry();
}
return outputBuilder.build();
}
}