io.trino.operator.HashGenerator 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.trino.operator;
import io.trino.spi.Page;
public interface HashGenerator
{
long hashPosition(int position, Page page);
default int getPartition(int partitionCount, int position, Page page)
{
long rawHash = hashPosition(position, page);
// This function reduces the 64 bit rawHash to [0, partitionCount) uniformly. It first reduces the rawHash to 32 bit
// integer x then normalize it to x / 2^32 * partitionCount to reduce the range of x from [0, 2^32) to [0, partitionCount)
return (int) ((Integer.toUnsignedLong(Long.hashCode(rawHash)) * partitionCount) >>> 32);
}
}