xiangfu0 commented on code in PR #17872: URL: https://github.com/apache/pinot/pull/17872#discussion_r2993267498
########## pinot-core/src/main/java/org/apache/pinot/core/operator/query/InvertedIndexDistinctOperator.java: ########## @@ -0,0 +1,507 @@ +/** + * 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.pinot.core.operator.query; + +import com.google.common.base.CaseFormat; +import java.util.Collections; +import java.util.List; +import java.util.NavigableMap; +import java.util.TreeMap; +import java.util.stream.Collectors; +import javax.annotation.Nullable; +import org.apache.pinot.common.request.context.ExpressionContext; +import org.apache.pinot.common.request.context.OrderByExpressionContext; +import org.apache.pinot.common.utils.DataSchema; +import org.apache.pinot.common.utils.DataSchema.ColumnDataType; +import org.apache.pinot.common.utils.config.QueryOptionsUtils; +import org.apache.pinot.core.common.Operator; +import org.apache.pinot.core.operator.BaseOperator; +import org.apache.pinot.core.operator.BaseProjectOperator; +import org.apache.pinot.core.operator.ExecutionStatistics; +import org.apache.pinot.core.operator.ExplainAttributeBuilder; +import org.apache.pinot.core.operator.blocks.DocIdSetBlock; +import org.apache.pinot.core.operator.blocks.ValueBlock; +import org.apache.pinot.core.operator.blocks.results.DistinctResultsBlock; +import org.apache.pinot.core.operator.filter.BaseFilterOperator; +import org.apache.pinot.core.operator.filter.BitmapBasedFilterOperator; +import org.apache.pinot.core.plan.DocIdSetPlanNode; +import org.apache.pinot.core.plan.ProjectPlanNode; +import org.apache.pinot.core.query.distinct.DistinctExecutor; +import org.apache.pinot.core.query.distinct.DistinctExecutorFactory; +import org.apache.pinot.core.query.distinct.table.DictIdDistinctTable; +import org.apache.pinot.core.query.request.context.QueryContext; +import org.apache.pinot.segment.spi.IndexSegment; +import org.apache.pinot.segment.spi.SegmentContext; +import org.apache.pinot.segment.spi.datasource.DataSource; +import org.apache.pinot.segment.spi.datasource.DataSourceMetadata; +import org.apache.pinot.segment.spi.index.reader.Dictionary; +import org.apache.pinot.segment.spi.index.reader.InvertedIndexReader; +import org.apache.pinot.segment.spi.index.reader.NullValueVectorReader; +import org.apache.pinot.segment.spi.index.reader.SortedIndexReader; +import org.apache.pinot.spi.query.QueryThreadContext; +import org.apache.pinot.spi.utils.Pairs; +import org.roaringbitmap.PeekableIntIterator; +import org.roaringbitmap.buffer.ImmutableRoaringBitmap; +import org.roaringbitmap.buffer.MutableRoaringBitmap; + + +/** + * Inverted-index-based operator for single-column distinct queries on a single segment. + * + * <p>Supports three execution paths, chosen at runtime: + * <ul> + * <li><b>Sorted index path</b>: For sorted columns, merge-iterates filter bitmap against contiguous doc ranges. + * Cost ~ O(cardinality + filteredDocs). Always chosen when the column has a sorted forward index.</li> + * <li><b>Bitmap inverted index path</b>: Iterates dictionary entries and uses inverted index bitmap intersections + * to check filter membership. Avoids the projection pipeline entirely. Chosen by cost heuristic when dictionary + * cardinality is much smaller than the filtered doc count.</li> + * <li><b>Scan path (fallback)</b>: Uses ProjectOperator + DistinctExecutor to scan filtered docs. + * Used when the cost heuristic determines scanning is cheaper.</li> + * </ul> + * + * <p>Enabled via the {@code useIndexBasedDistinctOperator} query option. The cost ratio can be tuned + * via the {@code invertedIndexDistinctCostRatio} query option. + */ +public class InvertedIndexDistinctOperator extends BaseOperator<DistinctResultsBlock> { + private static final String EXPLAIN_NAME = "DISTINCT_INVERTED_INDEX"; + private static final String EXPLAIN_NAME_SORTED_INDEX = "DISTINCT_SORTED_INDEX"; + private static final String EXPLAIN_NAME_SCAN_FALLBACK = "DISTINCT"; + + private final IndexSegment _indexSegment; + private final SegmentContext _segmentContext; + private final QueryContext _queryContext; + private final BaseFilterOperator _filterOperator; + private final DataSource _dataSource; + private final Dictionary _dictionary; + private final InvertedIndexReader<?> _invertedIndexReader; + + // Scan path: created lazily when scan fallback is chosen + private BaseProjectOperator<?> _projectOperator; + + // Execution tracking + private boolean _usedInvertedIndexPath = false; + private int _numDocsScanned = 0; + private int _numEntriesExamined = 0; + private long _numEntriesScannedInFilter = 0; + + /** + * Creates an InvertedIndexDistinctOperator. The caller (DistinctPlanNode) must verify that the column + * has both a dictionary and an inverted index before constructing this operator. + */ + public InvertedIndexDistinctOperator(IndexSegment indexSegment, SegmentContext segmentContext, + QueryContext queryContext, BaseFilterOperator filterOperator, DataSource dataSource) { + _indexSegment = indexSegment; + _segmentContext = segmentContext; + _queryContext = queryContext; + _filterOperator = filterOperator; + _dataSource = dataSource; + _dictionary = dataSource.getDictionary(); + _invertedIndexReader = dataSource.getInvertedIndex(); + } + + @Override + protected DistinctResultsBlock getNextBlock() { + ImmutableRoaringBitmap filteredDocIds = buildFilteredDocIds(); + + // Sorted index: always use the sorted path — O(cardinality + filteredDocs) merge iteration + if (_invertedIndexReader instanceof SortedIndexReader) { + _usedInvertedIndexPath = true; + return executeSortedIndexPath((SortedIndexReader<?>) _invertedIndexReader, filteredDocIds); + } + // Bitmap inverted index: use cost heuristic to decide + if (shouldUseBitmapInvertedIndex(filteredDocIds)) { + _usedInvertedIndexPath = true; + return executeInvertedIndexPath(filteredDocIds); + } + return executeScanPath(filteredDocIds); + } + + // ==================== Cost Heuristic ==================== + + /** + * Default cost ratios for the inverted-index-based distinct heuristic, keyed by dictionary cardinality threshold. + * The inverted index path is chosen when {@code dictionaryCardinality * costRatio <= filteredDocCount}. + * + * <p>The cost ratio accounts for the per-entry bitmap intersection cost relative to the per-doc scan cost. + * For low-cardinality dictionaries, each bitmap is dense and {@code intersects()} is fast, but there are few + * entries so any unnecessary intersection is relatively expensive vs. scanning a small filtered doc set. + * For high-cardinality dictionaries, bitmaps are sparser and {@code intersects()} is slower per entry, + * but the scan path also becomes cheaper (fewer docs per value), so a lower ratio suffices. + * + * <p>Benchmarking (BenchmarkInvertedIndexDistinct, 1M docs) shows the crossover points: + * <ul> + * <li>dictCard ≤ 1K: costRatio=30 — inverted index wins when filteredDocs ≥ ~30x dictCard</li> + * <li>dictCard ≤ 10K: costRatio=10 — inverted index wins when filteredDocs ≥ ~10x dictCard</li> + * <li>dictCard > 10K: costRatio=6 — inverted index wins when filteredDocs ≥ ~6x dictCard</li> + * </ul> + * + * <p>Can be overridden at query time via the query option {@code invertedIndexDistinctCostRatio}. + */ + static final NavigableMap<Integer, Double> DEFAULT_COST_RATIO_BY_CARDINALITY; + + static { + TreeMap<Integer, Double> map = new TreeMap<>(); + map.put(0, 30.0); // dictCard <= 1000: costRatio = 30 + map.put(1_001, 10.0); // dictCard 1001..10000: costRatio = 10 + map.put(10_001, 6.0); // dictCard > 10000: costRatio = 6 + DEFAULT_COST_RATIO_BY_CARDINALITY = Collections.unmodifiableNavigableMap(map); + } + + static double getDefaultCostRatio(int dictionaryCardinality) { + return DEFAULT_COST_RATIO_BY_CARDINALITY.floorEntry(dictionaryCardinality).getValue(); + } + + private boolean shouldUseBitmapInvertedIndex(@Nullable ImmutableRoaringBitmap filteredDocIds) { + int dictionaryCardinality = _dictionary.length(); + int filteredDocCount = filteredDocIds == null + ? _indexSegment.getSegmentMetadata().getTotalDocs() + : filteredDocIds.getCardinality(); + if (filteredDocCount == 0) { + return false; + } + Double costRatioOverride = QueryOptionsUtils.getInvertedIndexDistinctCostRatio(_queryContext.getQueryOptions()); + double costRatio = costRatioOverride != null ? costRatioOverride : getDefaultCostRatio(dictionaryCardinality); + return (double) dictionaryCardinality * costRatio <= filteredDocCount; + } + + // ==================== Scan Path (Fallback) ==================== + + /** + * Scan fallback: uses ProjectOperator + DistinctExecutor. When the filter bitmap was already materialized + * by {@link #buildFilteredDocIds()}, wraps it in a {@link BitmapBasedFilterOperator} to avoid re-evaluating + * the filter through the projection pipeline. + */ + private DistinctResultsBlock executeScanPath(@Nullable ImmutableRoaringBitmap filteredDocIds) { + BaseFilterOperator filterOp; + if (filteredDocIds != null) { + filterOp = new BitmapBasedFilterOperator(filteredDocIds, false, + _indexSegment.getSegmentMetadata().getTotalDocs()); + } else { + filterOp = _filterOperator; + } + _projectOperator = new ProjectPlanNode(_segmentContext, _queryContext, + _queryContext.getSelectExpressions(), DocIdSetPlanNode.MAX_DOC_PER_CALL, filterOp).run(); + DistinctExecutor executor = DistinctExecutorFactory.getDistinctExecutor(_projectOperator, _queryContext); + ValueBlock valueBlock; + while ((valueBlock = _projectOperator.nextBlock()) != null) { + _numDocsScanned += valueBlock.getNumDocs(); + if (executor.process(valueBlock)) { + break; + } + } + return new DistinctResultsBlock(executor.getResult(), _queryContext); + } + + // ==================== Sorted Index Path ==================== + + /** + * Optimized path for sorted columns. Each dictId maps to a contiguous doc range [start, end]. + * We merge-iterate the filter bitmap with the sorted ranges in O(cardinality + filteredDocs). + */ + private DistinctResultsBlock executeSortedIndexPath(SortedIndexReader<?> sortedReader, + @Nullable ImmutableRoaringBitmap filteredDocIds) { + DictIdDistinctTable dictIdTable = createDictIdTable(); + OrderByExpressionContext orderByExpression = + _queryContext.getOrderByExpressions() != null ? _queryContext.getOrderByExpressions().get(0) : null; + int dictLength = _dictionary.length(); + // Process null handling: exclude null docs from filter and determine if nulls are present + NullFilterResult nullResult = processNullDocs(filteredDocIds); + ImmutableRoaringBitmap nonNullFilteredDocIds = nullResult._nonNullFilteredDocIds; + Review Comment: Handled. Both the sorted-index and bitmap-inverted paths now reserve the null slot as soon as `processNullDocs()` reports it, before collecting non-null values, so LIMIT no longer crowds null out of the final result. -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
