ChrisHegarty commented on code in PR #15011: URL: https://github.com/apache/lucene/pull/15011#discussion_r2272744054
########## lucene/core/src/java/org/apache/lucene/search/AcceptDocs.java: ########## @@ -0,0 +1,181 @@ +/* + * 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. + * + * @return Bits instance for random access, or null if not available + * @throws IOException if an I/O error occurs + */ + public abstract Bits bits() throws IOException; + + /** + * Get an iterator of accepted docs. + * + * @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. + * + * @return approximate cost + */ + public abstract int cost(); + + /** + * 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) { + return new BitSetAcceptDocs(bitSet); + } + 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 { + BitSet bitSet = createBitSet(iterator, liveDocs, maxDoc); + return new BitSetAcceptDocs(bitSet); + } + + 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 { + FilteredDocIdSetIterator filterIterator = + new FilteredDocIdSetIterator(iterator) { + @Override + protected boolean match(int doc) { + return liveDocs == null || liveDocs.get(doc); + } + }; + return BitSet.of(filterIterator, 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 int maxDoc; + + BitsAcceptDocs(Bits bits, int maxDoc) { + this.bits = bits; + this.maxDoc = maxDoc; + } + + @Override + public Bits bits() { + return bits; + } + + @Override + public DocIdSetIterator iterator() { + DocIdSetIterator iterator = DocIdSetIterator.all(maxDoc); + if (bits != null) { + iterator = + new FilteredDocIdSetIterator(iterator) { + @Override + protected boolean match(int doc) { + return bits.get(doc); + } + }; + } + 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 BitSet} */ + private static class BitSetAcceptDocs extends AcceptDocs { + + private final BitSet bitSet; + private int cardinality = -1; + + BitSetAcceptDocs(BitSet bitSet) { + this.bitSet = bitSet; + } + + @Override + public Bits bits() throws IOException { + return bitSet; + } + + @Override + public DocIdSetIterator iterator() throws IOException { + return new BitSetIterator(bitSet, cost()); + } + + @Override + public synchronized int cost() { Review Comment: why is this `synchronized`? I there any expectation of thread-safety of AcceptedDocs ? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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