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

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

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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.lucene.index;

import java.util.List;

import org.apache.lucene.util.Bits;

/**
 * Concatenates multiple Bits together, on every lookup.
 *
 * <p><b>NOTE</b>: This is very costly, as every lookup must
 * do a binary search to locate the right sub-reader.
 *
 * @lucene.experimental
 */
public final class MultiBits implements Bits {
    private final Bits[] subs;

    // length is 1+subs.length (the last entry has the maxDoc):
    private final int[] starts;

    private final boolean defaultValue;

    private MultiBits(Bits[] subs, int[] starts, boolean defaultValue) {
        assert starts.length == 1 + subs.length;
        this.subs = subs;
        this.starts = starts;
        this.defaultValue = defaultValue;
    }

    /** Returns a single {@link Bits} instance for this
     *  reader, merging live Documents on the
     *  fly.  This method will return null if the reader
     *  has no deletions.
     *
     *  <p><b>NOTE</b>: this is a very slow way to access live docs.
     *  For example, each Bits access will require a binary search.
     *  It's better to get the sub-readers and iterate through them
     *  yourself. */
    public static Bits getLiveDocs(IndexReader reader) {
        if (reader.hasDeletions()) {
            final List<LeafReaderContext> leaves = reader.leaves();
            final int size = leaves.size();
            assert size > 0 : "A reader with deletions must have at least one leave";
            if (size == 1) {
                return leaves.get(0).reader().getLiveDocs();
            }
            final Bits[] liveDocs = new Bits[size];
            final int[] starts = new int[size + 1];
            for (int i = 0; i < size; i++) {
                // record all liveDocs, even if they are null
                final LeafReaderContext ctx = leaves.get(i);
                liveDocs[i] = ctx.reader().getLiveDocs();
                starts[i] = ctx.docBase;
            }
            starts[size] = reader.maxDoc();
            return new MultiBits(liveDocs, starts, true);
        } else {
            return null;
        }
    }

    private boolean checkLength(int reader, int doc) {
        final int length = starts[1 + reader] - starts[reader];
        assert doc - starts[reader] < length : "doc=" + doc + " reader=" + reader + " starts[reader]="
                + starts[reader] + " length=" + length;
        return true;
    }

    @Override
    public boolean get(int doc) {
        final int reader = ReaderUtil.subIndex(doc, starts);
        assert reader != -1;
        final Bits bits = subs[reader];
        if (bits == null) {
            return defaultValue;
        } else {
            assert checkLength(reader, doc);
            return bits.get(doc - starts[reader]);
        }
    }

    @Override
    public String toString() {
        StringBuilder b = new StringBuilder();
        b.append(subs.length).append(" subs: ");
        for (int i = 0; i < subs.length; i++) {
            if (i != 0) {
                b.append("; ");
            }
            if (subs[i] == null) {
                b.append("s=").append(starts[i]).append(" l=null");
            } else {
                b.append("s=").append(starts[i]).append(" l=").append(subs[i].length()).append(" b=")
                        .append(subs[i]);
            }
        }
        b.append(" end=").append(starts[subs.length]);
        return b.toString();
    }

    @Override
    public int length() {
        return starts[starts.length - 1];
    }
}