io.prestosql.operator.scalar.ArrayReverseFunction Maven / Gradle / Ivy
/*
* 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 io.prestosql.operator.scalar;
import com.google.common.collect.ImmutableList;
import io.prestosql.spi.PageBuilder;
import io.prestosql.spi.block.Block;
import io.prestosql.spi.block.BlockBuilder;
import io.prestosql.spi.function.Description;
import io.prestosql.spi.function.ScalarFunction;
import io.prestosql.spi.function.SqlType;
import io.prestosql.spi.function.TypeParameter;
import io.prestosql.spi.type.Type;
@ScalarFunction("reverse")
@Description("Returns an array which has the reversed order of the given array.")
public final class ArrayReverseFunction
{
private final PageBuilder pageBuilder;
@TypeParameter("E")
public ArrayReverseFunction(@TypeParameter("E") Type elementType)
{
pageBuilder = new PageBuilder(ImmutableList.of(elementType));
}
@TypeParameter("E")
@SqlType("array(E)")
public Block reverse(
@TypeParameter("E") Type type,
@SqlType("array(E)") Block block)
{
int arrayLength = block.getPositionCount();
if (arrayLength < 2) {
return block;
}
if (pageBuilder.isFull()) {
pageBuilder.reset();
}
BlockBuilder blockBuilder = pageBuilder.getBlockBuilder(0);
for (int i = arrayLength - 1; i >= 0; i--) {
type.appendTo(block, i, blockBuilder);
}
pageBuilder.declarePositions(arrayLength);
return blockBuilder.getRegion(blockBuilder.getPositionCount() - arrayLength, arrayLength);
}
}