goankur commented on a change in pull request #1893: URL: https://github.com/apache/lucene-solr/pull/1893#discussion_r494675000
########## File path: lucene/facet/src/java/org/apache/lucene/facet/taxonomy/TaxonomyFacetLabels.java ########## @@ -0,0 +1,184 @@ +/* + * 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.facet.taxonomy; + +import org.apache.lucene.facet.FacetsConfig; +import org.apache.lucene.index.LeafReaderContext; +import org.apache.lucene.util.IntsRef; + +import java.io.IOException; + +import static org.apache.lucene.facet.taxonomy.TaxonomyReader.INVALID_ORDINAL; +import static org.apache.lucene.facet.taxonomy.TaxonomyReader.ROOT_ORDINAL; + +/** + * Utility class to easily retrieve previously indexed facet labels, allowing you to skip also adding stored fields for these values, + * reducing your index size. + * + * @lucene.experimental + **/ +public class TaxonomyFacetLabels { + + /** + * Index field name provided to the constructor + */ + private final String indexFieldName; + + /** + * {@code TaxonomyReader} provided to the constructor + */ + private final TaxonomyReader taxoReader; + + /** + * {@code FacetsConfig} provided to the constructor + */ + private final FacetsConfig config; + + /** + * {@code OrdinalsReader} to decode ordinals previously indexed into the {@code BinaryDocValues} facet field + */ + private final OrdinalsReader ordsReader; + + /** + * Sole constructor. Do not close the provided {@link TaxonomyReader} while still using this instance! + */ + public TaxonomyFacetLabels(TaxonomyReader taxoReader, FacetsConfig config, String indexFieldName) throws IOException { + this.taxoReader = taxoReader; + this.config = config; + this.indexFieldName = indexFieldName; + this.ordsReader = new DocValuesOrdinalsReader(indexFieldName); + } + + /** + * Create and return an instance of {@link FacetLabelReader} to retrieve facet labels for + * multiple documents and (optionally) for a specific dimension. You must create this per-segment, + * and then step through all hits, in order, for that segment. + * + * <p><b>NOTE</b>: This class is not thread-safe, so you must use a new instance of this + * class for each thread.</p> + * + * @param readerContext LeafReaderContext used to access the {@code BinaryDocValues} facet field + * @return an instance of {@link FacetLabelReader} + * @throws IOException when a low-level IO issue occurs + */ + public FacetLabelReader getFacetLabelReader(LeafReaderContext readerContext) throws IOException { + return new FacetLabelReader(ordsReader, readerContext); + } + + /** + * Utility class to retrieve facet labels for multiple documents. + * + * @lucene.experimental + */ + public class FacetLabelReader { + private final OrdinalsReader.OrdinalsSegmentReader ordinalsSegmentReader; + private final IntsRef decodedOrds = new IntsRef(); + private int currentDocId = -1; + private int currentPos = -1; + + // Lazily set when nextFacetLabel(int docId, String facetDimension) is first called + private int[] parents; + + /** + * Sole constructor. + */ + public FacetLabelReader(OrdinalsReader ordsReader, LeafReaderContext readerContext) throws IOException { + ordinalsSegmentReader = ordsReader.getReader(readerContext); + } + + /** + * Retrieves the next {@link FacetLabel} for the specified {@code docId}, or {@code null} if there are no more. + * This method has state: if the provided {@code docId} is the same as the previous invocation, it returns the + * next {@link FacetLabel} for that document. Otherwise, it advances to the new {@code docId} and provides the + * first {@link FacetLabel} for that document, or {@code null} if that document has no indexed facets. Each + * new {@code docId} must be in strictly monotonic (increasing) order. + * + * @param docId input docId provided in monotonic (non-decreasing) order + * @return the first or next {@link FacetLabel}, or {@code null} if there are no more + * @throws IOException when a low-level IO issue occurs + */ + public FacetLabel nextFacetLabel(int docId) throws IOException { + if (currentDocId != docId) { + assert docId > currentDocId: "docs out of order! currentDocId=" + currentDocId + " docId=" + docId; + ordinalsSegmentReader.get(docId, decodedOrds); + currentDocId = docId; + currentPos = decodedOrds.offset; + } + + int endPos = decodedOrds.offset + decodedOrds.length; + assert currentPos <= endPos; + + if (currentPos == endPos) { + // no more FacetLabels + return null; + } + + int ord = decodedOrds.ints[currentPos++]; + return taxoReader.getPath(ord); + } + + private boolean isDescendant(int ord, int ancestorOrd) { + while (ord != INVALID_ORDINAL && ord != ROOT_ORDINAL) { + if (parents[ord] == ancestorOrd) { + return true; + } + ord = parents[ord]; + } + return false; + } + + /** + * Retrieves the next {@link FacetLabel} for the specified {@code docId} under the requested {@code facetDimension}, + * or {@code null} if there are no more. This method has state: if the provided {@code docId} is the same as the + * previous invocation, it returns the next {@link FacetLabel} for that document. Otherwise, it advances to + * the new {@code docId} and provides the first {@link FacetLabel} for that document, or {@code null} if that document + * has no indexed facets. Each new {@code docId} must be in strictly monotonic (increasing) order. + * + * <p><b>NOTE</b>: this method loads the {@code int[] parents} array from the taxonomy index</p> + * + * @param docId input docId provided in non-decreasing order + * @return the first or next {@link FacetLabel}, or {@code null} if there are no more + * @throws IOException if {@link TaxonomyReader} has problems getting path for an ordinal + */ + public FacetLabel nextFacetLabel(int docId, String facetDimension) throws IOException { + final int parentOrd = taxoReader.getOrdinal(new FacetLabel(facetDimension)); + assert parentOrd != INVALID_ORDINAL : "Category ordinal not found for facet dimension: " + facetDimension; + + if (currentDocId != docId) { + assert docId > currentDocId: "docs out of order! currentDocId=" + currentDocId + " docId=" + docId; + ordinalsSegmentReader.get(docId, decodedOrds); + currentPos = decodedOrds.offset; + currentDocId = docId; + } + + if (parents == null) { + parents = taxoReader.getParallelTaxonomyArrays().parents(); + } + + int endPos = decodedOrds.offset + decodedOrds.length; + assert currentPos <= endPos; + + for (; currentPos < endPos; ) { + int ord = decodedOrds.ints[currentPos++]; + if (isDescendant(ord, parentOrd) == true) { + return taxoReader.getPath(ord); Review comment: The new per-segment class (`FacetLabelReader`) holds an instance of `DocValuesOrdinalsReader` which internally holds a reusable instance of `BinaryDocValues`. In the `nextFacetLabel()` method `ordinalsSegmentReader.get(docId, decodedOrds)` that does the actual decoding of the ordinals is only called **once** if the input docId is the same as the one supplied in prior invocation of `nextFacetLabel()`. Subsequent invocations fetch the ordinals from `FacetLabelReader.decodedOrds` and use the ordinal to lookup FacetLabels using `taxoReader.getPath(ord)`. Yes, after LUCENE-9450, we can bulk resolve all the ordinals using a different API, something like -> `List<FacetLabels> taxoReader.getPaths(IntRef decodedOrds)` and add a new API - `FacetLabelReader.allFacetLabels(int docId)` ---------------------------------------------------------------- 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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