/*
* 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.operator.aggregation.TypedSet;
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.function.Description;
import com.facebook.presto.spi.function.ScalarFunction;
import com.facebook.presto.spi.function.SqlType;
import com.facebook.presto.spi.function.TypeParameter;
import com.facebook.presto.spi.type.Type;
@ScalarFunction("array_except")
@Description("Returns an array of elements that are in the first array but not the second, without duplicates.")
public final class ArrayExceptFunction
{
private ArrayExceptFunction() {}
@TypeParameter("E")
@SqlType("array(E)")
public static Block except(
@TypeParameter("E") Type type,
@SqlType("array(E)") Block leftArray,
@SqlType("array(E)") Block rightArray)
{
int leftPositionCount = leftArray.getPositionCount();
int rightPositionCount = rightArray.getPositionCount();
if (leftPositionCount == 0) {
return leftArray;
}
TypedSet typedSet = new TypedSet(type, leftPositionCount + rightPositionCount);
BlockBuilder distinctElementBlockBuilder = type.createBlockBuilder(new BlockBuilderStatus(), leftPositionCount);
for (int i = 0; i < rightPositionCount; i++) {
typedSet.add(rightArray, i);
}
for (int i = 0; i < leftPositionCount; i++) {
if (!typedSet.contains(leftArray, i)) {
typedSet.add(leftArray, i);
type.appendTo(leftArray, i, distinctElementBlockBuilder);
}
}
return distinctElementBlockBuilder.build();
}
}