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Copy pathVectorRangeSearcher.java
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108 lines (96 loc) · 3.76 KB
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.arrow.algorithm.search;
import org.apache.arrow.algorithm.sort.VectorValueComparator;
import org.apache.arrow.vector.ValueVector;
/**
* Search for the range of a particular element in the target vector.
*/
public class VectorRangeSearcher {
/**
* Result returned when a search fails.
*/
public static final int SEARCH_FAIL_RESULT = -1;
/**
* Search for the first occurrence of an element.
* The search is based on the binary search algorithm. So the target vector must be sorted.
* @param targetVector the vector from which to perform the search.
* @param comparator the criterion for the comparison.
* @param keyVector the vector containing the element to search.
* @param keyIndex the index of the search key in the key vector.
* @param <V> the vector type.
* @return the index of the first matched element if any, and -1 otherwise.
*/
public static <V extends ValueVector> int getFirstMatch(
V targetVector, VectorValueComparator<V> comparator, V keyVector, int keyIndex) {
comparator.attachVectors(keyVector, targetVector);
int ret = SEARCH_FAIL_RESULT;
int low = 0;
int high = targetVector.getValueCount() - 1;
while (low <= high) {
int mid = low + (high - low) / 2;
int result = comparator.compare(keyIndex, mid);
if (result < 0) {
// the key is smaller
high = mid - 1;
} else if (result > 0) {
// the key is larger
low = mid + 1;
} else {
// an equal element is found
// continue to go left-ward
ret = mid;
high = mid - 1;
}
}
return ret;
}
/**
* Search for the last occurrence of an element.
* The search is based on the binary search algorithm. So the target vector must be sorted.
* @param targetVector the vector from which to perform the search.
* @param comparator the criterion for the comparison.
* @param keyVector the vector containing the element to search.
* @param keyIndex the index of the search key in the key vector.
* @param <V> the vector type.
* @return the index of the last matched element if any, and -1 otherwise.
*/
public static <V extends ValueVector> int getLastMatch(
V targetVector, VectorValueComparator<V> comparator, V keyVector, int keyIndex) {
comparator.attachVectors(keyVector, targetVector);
int ret = SEARCH_FAIL_RESULT;
int low = 0;
int high = targetVector.getValueCount() - 1;
while (low <= high) {
int mid = low + (high - low) / 2;
int result = comparator.compare(keyIndex, mid);
if (result < 0) {
// the key is smaller
high = mid - 1;
} else if (result > 0) {
// the key is larger
low = mid + 1;
} else {
// an equal element is found,
// continue to go right-ward
ret = mid;
low = mid + 1;
}
}
return ret;
}
}