jpountz commented on code in PR #15011: URL: https://github.com/apache/lucene/pull/15011#discussion_r2281033550
########## lucene/core/src/java/org/apache/lucene/search/AcceptDocs.java: ########## @@ -0,0 +1,221 @@ +/* + * 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.search; + +import java.io.IOException; +import org.apache.lucene.index.LeafReader; +import org.apache.lucene.util.BitSet; +import org.apache.lucene.util.BitSetIterator; +import org.apache.lucene.util.Bits; +import org.apache.lucene.util.FixedBitSet; + +/** + * Higher-level abstraction for document acceptance filtering. Can be consumed in either + * random-access (Bits) or sequential (DocIdSetIterator) pattern. + * + * @lucene.experimental + */ +public abstract class AcceptDocs { + + /** + * Random access to the accepted documents. + * + * <p><b>NOTE</b>: This must not be called if the {@link #iterator()} has already been used. + * + * @return Bits instance for random access, or null if all documents are accepted + * @throws IOException if an I/O error occurs + */ + public abstract Bits bits() throws IOException; + + /** + * Get an iterator of accepted docs. + * + * <p><b>NOTE</b>: This method doesn't return a new iterator, but a reference to a shared + * instance. + * + * @return DocIdSetIterator for sequential access + * @throws IOException if an I/O error occurs + */ + public abstract DocIdSetIterator iterator() throws IOException; + + /** + * Return an approximation of the number of accepted documents. This is typically useful to decide + * whether to consume these accept docs using random access ({@link #bits()}) or sequential access + * ({@link #iterator()}). + * + * <p><b>NOTE</b>: This must not be called if the {@link #iterator()} has already been used. + * + * @return approximate cost + */ + public abstract int cost() throws IOException; + + /** + * Create AcceptDocs from a {@link Bits} instance representing live documents. A {@code null} + * instance is interpreted as matching all documents, like in {@link LeafReader#getLiveDocs()}. + * + * @param bits the Bits instance for random access + * @param maxDoc the number of documents in the reader + * @return AcceptDocs wrapping the Bits + */ + public static AcceptDocs fromLiveDocs(Bits bits, int maxDoc) { + if (bits instanceof BitSet bitSet) { + DocIdSetIterator iterator = new BitSetIterator(bitSet, bitSet.approximateCardinality()); + return new DocIdSetIteratorAcceptDocs(iterator, null, maxDoc); + } + return new BitsAcceptDocs(bits, maxDoc); + } + + /** + * Create AcceptDocs from a DocIdSetIterator, optionally filtered by live documents. + * + * @param iterator a DocIdSetIterator iterator + * @param liveDocs Bits representing live documents, or {@code null} if no deleted docs + * @param maxDoc the number of documents in the reader + * @return AcceptDocs wrapping the iterator + */ + public static AcceptDocs fromIterator(DocIdSetIterator iterator, Bits liveDocs, int maxDoc) + throws IOException { + return new DocIdSetIteratorAcceptDocs(iterator, liveDocs, maxDoc); + } + + private static BitSet createBitSet(DocIdSetIterator iterator, Bits liveDocs, int maxDoc) + throws IOException { + if (liveDocs == null && iterator instanceof BitSetIterator bitSetIterator) { + // If we already have a BitSet and no deletions, reuse the BitSet + return bitSetIterator.getBitSet(); + } else { + int threshold = maxDoc >> 7; // same as BitSet#of + if (iterator.cost() >= threshold) { + // take advantage of Disi#intoBitset and Bits#applyMask + FixedBitSet bitSet = new FixedBitSet(maxDoc); + bitSet.or(iterator); + if (liveDocs != null) { + liveDocs.applyMask(bitSet, 0); + } + return bitSet; + } else { + if (liveDocs != null) { + iterator = + new FilteredDocIdSetIterator(iterator) { + @Override + protected boolean match(int doc) { + return liveDocs.get(doc); + } + }; + } + return BitSet.of(iterator, maxDoc); // create a sparse bitset + } + } + } + + /** Impl backed by Bits, expected to be somewhat dense. */ + private static class BitsAcceptDocs extends AcceptDocs { + private final Bits bits; + private final DocIdSetIterator iterator; + private final int maxDoc; + + BitsAcceptDocs(Bits bits, int maxDoc) { + this.bits = bits; + this.maxDoc = maxDoc; + DocIdSetIterator iterator = DocIdSetIterator.all(maxDoc); + if (bits != null) { + iterator = + new FilteredDocIdSetIterator(iterator) { + @Override + protected boolean match(int doc) { + return bits.get(doc); + } + }; + } + this.iterator = iterator; + } + + @Override + public Bits bits() { + return bits; + } + + @Override + public DocIdSetIterator iterator() { + return iterator; + } + + @Override + public int cost() { + // We have no better estimate. This should be ok in practice since background merges should + // keep the number of deletes under control (< 20% by default). + return maxDoc; + } + } + + /** Impl backed by a {@link DocIdSetIterator} */ + private static class DocIdSetIteratorAcceptDocs extends AcceptDocs { + + private final Bits liveDocs; + private final int maxDoc; + + private DocIdSetIterator iterator; + private BitSet bitSet = null; + private int cardinality = -1; + + DocIdSetIteratorAcceptDocs(DocIdSetIterator iterator, Bits liveDocs, int maxDoc) { + this.iterator = iterator; + this.liveDocs = liveDocs; + this.maxDoc = maxDoc; + if (iterator.docID() != -1) { + throw new IllegalArgumentException( + "Iterator must be unpositioned, but got current doc ID: " + iterator.docID()); + } + } + + /** + * The {@link BitSet} is computed lazily so that it is never created in case only the {@link + * #iterator} is needed + */ + private void loadIntoBitSetIfNecessary() throws IOException { + // Usage of AcceptDocs should be confined to a single thread, so this doesn't need + // synchronization. + if (bitSet == null) { + if (iterator.docID() != -1) { Review Comment: It's not checked all the time. -- This is an automated message from the Apache Git Service. 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