package org.apache.lucene.index;
/*
* 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.
*/
import org.apache.lucene.util.BytesRef;
/**
* A per-document byte[] with presorted values.
* <p>
* Per-Document values in a SortedDocValues are deduplicated, dereferenced,
* and sorted into a dictionary of unique values. A pointer to the
* dictionary value (ordinal) can be retrieved for each document. Ordinals
* are dense and in increasing sorted order.
*/
public abstract class SortedDocValues extends BinaryDocValues {
/** Sole constructor. (For invocation by subclass
* constructors, typically implicit.) */
protected SortedDocValues() {}
/**
* Returns the ordinal for the specified docID.
* @param docID document ID to lookup
* @return ordinal for the document: this is dense, starts at 0, then
* increments by 1 for the next value in sorted order. Note that
* missing values are indicated by -1.
*/
public abstract int getOrd(int docID);
/** Retrieves the value for the specified ordinal.
* @param ord ordinal to lookup (must be >= 0 and < {@link #getValueCount()})
* @param result will be populated with the ordinal's value
* @see #getOrd(int)
*/
public abstract void lookupOrd(int ord, BytesRef result);
/**
* Returns the number of unique values.
* @return number of unique values in this SortedDocValues. This is
* also equivalent to one plus the maximum ordinal.
*/
public abstract int getValueCount();
@Override
public void get(int docID, BytesRef result) {
int ord = getOrd(docID);
if (ord == -1) {
result.bytes = BytesRef.EMPTY_BYTES;
result.length = 0;
result.offset = 0;
} else {
lookupOrd(ord, result);
}
}
/** An empty SortedDocValues which returns {@link BytesRef#EMPTY_BYTES} for every document */
public static final SortedDocValues EMPTY = new SortedDocValues() {
@Override
public int getOrd(int docID) {
return -1;
}
@Override
public void lookupOrd(int ord, BytesRef result) {
result.bytes = BytesRef.EMPTY_BYTES;
result.offset = 0;
result.length = 0;
}
@Override
public int getValueCount() {
return 0;
}
};
/** If {@code key} exists, returns its ordinal, else
* returns {@code -insertionPoint-1}, like {@code
* Arrays.binarySearch}.
*
* @param key Key to look up
**/
public int lookupTerm(BytesRef key) {
BytesRef spare = new BytesRef();
int low = 0;
int high = getValueCount()-1;
while (low <= high) {
int mid = (low + high) >>> 1;
lookupOrd(mid, spare);
int cmp = spare.compareTo(key);
if (cmp < 0) {
low = mid + 1;
} else if (cmp > 0) {
high = mid - 1;
} else {
return mid; // key found
}
}
return -(low + 1); // key not found.
}
/**
* Returns a {@link TermsEnum} over the values.
* The enum supports {@link TermsEnum#ord()} and {@link TermsEnum#seekExact(long)}.
*/
public TermsEnum termsEnum() {
return new SortedDocValuesTermsEnum(this);
}
}