org.apache.lucene.index.SortedDocValues.java Source code

Introduction

Here is the source code for org.apache.lucene.index.SortedDocValues.java

Source

/*
 * 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.lucene.index;

import java.io.IOException;

import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.automaton.CompiledAutomaton;

/**
 * A per-document byte[] with presorted values.  This is fundamentally an
 * iterator over the int ord values per document, with random access APIs
 * to resolve an int ord to BytesRef.
 * <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 current docID.
     * It is illegal to call this method after {@link #advanceExact(int)}
     * returned {@code false}.
     * @return ordinal for the document: this is dense, starts at 0, then
     *         increments by 1 for the next value in sorted order.
     */
    public abstract int ordValue() throws IOException;

    /** Retrieves the value for the specified ordinal. The returned
     * {@link BytesRef} may be re-used across calls to {@link #lookupOrd(int)}
     * so make sure to {@link BytesRef#deepCopyOf(BytesRef) copy it} if you want
     * to keep it around.
     * @param ord ordinal to lookup (must be &gt;= 0 and &lt; {@link #getValueCount()})
     * @see #ordValue() 
     */
    public abstract BytesRef lookupOrd(int ord) throws IOException;

    private final BytesRef empty = new BytesRef();

    @Override
    public BytesRef binaryValue() throws IOException {
        int ord = ordValue();
        if (ord == -1) {
            return empty;
        } else {
            return lookupOrd(ord);
        }
    }

    /**
     * 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();

    /** 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) throws IOException {
        int low = 0;
        int high = getValueCount() - 1;

        while (low <= high) {
            int mid = (low + high) >>> 1;
            final BytesRef term = lookupOrd(mid);
            int cmp = term.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() throws IOException {
        return new SortedDocValuesTermsEnum(this);
    }

    /**
     * Returns a {@link TermsEnum} over the values, filtered by a {@link CompiledAutomaton}
     * The enum supports {@link TermsEnum#ord()}.
     */
    public TermsEnum intersect(CompiledAutomaton automaton) throws IOException {
        TermsEnum in = termsEnum();
        switch (automaton.type) {
        case NONE:
            return TermsEnum.EMPTY;
        case ALL:
            return in;
        case SINGLE:
            return new SingleTermsEnum(in, automaton.term);
        case NORMAL:
            return new AutomatonTermsEnum(in, automaton);
        default:
            // unreachable
            throw new RuntimeException("unhandled case");
        }
    }

}