gf2121 commented on code in PR #14333: URL: https://github.com/apache/lucene/pull/14333#discussion_r2035743271
########## lucene/core/src/java/org/apache/lucene/codecs/lucene103/blocktree/TrieBuilder.java: ########## @@ -0,0 +1,640 @@ +/* + * 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.codecs.lucene103.blocktree; + +import java.io.IOException; +import java.util.ArrayDeque; +import java.util.Arrays; +import java.util.Deque; +import java.util.function.BiConsumer; +import org.apache.lucene.store.DataOutput; +import org.apache.lucene.store.IndexOutput; +import org.apache.lucene.store.RandomAccessInput; +import org.apache.lucene.util.BytesRef; +import org.apache.lucene.util.BytesRefBuilder; + +/** + * A builder to build prefix tree (trie) as the index of block tree, and can be saved to disk. + * + * <p>TODO make this trie builder a more memory efficient structure. + */ +class TrieBuilder { + + static final int SIGN_NO_CHILDREN = 0x00; + static final int SIGN_SINGLE_CHILD_WITH_OUTPUT = 0x01; + static final int SIGN_SINGLE_CHILD_WITHOUT_OUTPUT = 0x02; + static final int SIGN_MULTI_CHILDREN = 0x03; + + static final int LEAF_NODE_HAS_TERMS = 1 << 5; + static final int LEAF_NODE_HAS_FLOOR = 1 << 6; + static final long NON_LEAF_NODE_HAS_TERMS = 1L << 1; + static final long NON_LEAF_NODE_HAS_FLOOR = 1L << 0; + + /** + * The output describing the term block the prefix point to. + * + * @param fp the file pointer to the on-disk terms block which a trie node points to. + * @param hasTerms false if this on-disk block consists entirely of pointers to child blocks. + * @param floorData will be non-null when a large block of terms sharing a single trie prefix is + * split into multiple on-disk blocks. + */ + record Output(long fp, boolean hasTerms, BytesRef floorData) {} + + private enum Status { + BUILDING, + SAVED, + DESTROYED + } + + private static class Node { + + // The utf8 digit that leads to this Node, 0 for root node + private final int label; + // The output of this node. + private Output output; + // The number of children of this node. + private int childrenNum; + // Pointers to relative nodes + private Node next; + private Node firstChild; + private Node lastChild; + + // Vars used during saving: + + // The file pointer point to where the node saved. -1 means the node has not been saved. + private long fp = -1; + // The latest child that have been saved. null means no child has been saved. + private Node savedTo; + + Node(int label, Output output) { + this.label = label; + this.output = output; + } + } + + private final Node root = new Node(0, null); + private final BytesRef minKey; + private BytesRef maxKey; + private Status status = Status.BUILDING; + + static TrieBuilder bytesRefToTrie(BytesRef k, Output v) { + return new TrieBuilder(k, v); + } + + private TrieBuilder(BytesRef k, Output v) { + minKey = maxKey = BytesRef.deepCopyOf(k); + if (k.length == 0) { + root.output = v; + return; + } + Node parent = root; + for (int i = 0; i < k.length; i++) { + int b = k.bytes[i + k.offset] & 0xFF; + Output output = i == k.length - 1 ? v : null; + Node node = new Node(b, output); + parent.firstChild = parent.lastChild = node; + parent.childrenNum = 1; + parent = node; + } + } + + /** + * Append all (K, V) pairs from the given trie into this one. The given trie builder need to + * ensure its keys greater or equals than max key of this one. + * + * <p>Note: the given trie will be destroyed after appending. + */ + void append(TrieBuilder trieBuilder) { + if (status != Status.BUILDING || trieBuilder.status != Status.BUILDING) { + throw new IllegalStateException("tries have wrong status."); + } + assert this.maxKey.compareTo(trieBuilder.minKey) < 0; + + int mismatch = + Arrays.mismatch( + this.maxKey.bytes, + this.maxKey.offset, + this.maxKey.offset + this.maxKey.length, + trieBuilder.minKey.bytes, + trieBuilder.minKey.offset, + trieBuilder.minKey.offset + trieBuilder.minKey.length); + Node a = this.root; + Node b = trieBuilder.root; + + for (int i = 0; i < mismatch; i++) { + final Node aLast = a.lastChild; + final Node bFirst = b.firstChild; + assert aLast.label == bFirst.label; + + if (b.childrenNum > 1) { + aLast.next = bFirst.next; + a.childrenNum += b.childrenNum - 1; + a.lastChild = b.lastChild; + assertChildrenLabelInOrder(a); Review Comment: Oops, yes! -- This is an automated message from the Apache Git Service. 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