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Subject [GitHub] [lucene-solr] jtibshirani commented on a change in pull request #715: LUCENE-7714 Add a range query that takes advantage of index sorting.
Date Wed, 12 Jun 2019 19:58:14 GMT
jtibshirani commented on a change in pull request #715: LUCENE-7714 Add a range query that
takes advantage of index sorting.
URL: https://github.com/apache/lucene-solr/pull/715#discussion_r293091329
 
 

 ##########
 File path: lucene/core/src/java/org/apache/lucene/document/IndexSortDocValuesRangeQuery.java
 ##########
 @@ -0,0 +1,279 @@
+/*
+ * 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.document;
+
+import java.io.IOException;
+import java.util.Objects;
+
+import org.apache.lucene.index.DocValues;
+import org.apache.lucene.index.LeafReader;
+import org.apache.lucene.index.LeafReaderContext;
+import org.apache.lucene.index.NumericDocValues;
+import org.apache.lucene.index.SortedNumericDocValues;
+import org.apache.lucene.search.BooleanClause;
+import org.apache.lucene.search.ConstantScoreScorer;
+import org.apache.lucene.search.ConstantScoreWeight;
+import org.apache.lucene.search.DocIdSetIterator;
+import org.apache.lucene.search.FieldComparator;
+import org.apache.lucene.search.IndexSearcher;
+import org.apache.lucene.search.LeafFieldComparator;
+import org.apache.lucene.search.Query;
+import org.apache.lucene.search.QueryVisitor;
+import org.apache.lucene.search.ScoreMode;
+import org.apache.lucene.search.Scorer;
+import org.apache.lucene.search.Sort;
+import org.apache.lucene.search.SortField;
+import org.apache.lucene.search.Weight;
+
+/**
+ * A range query that takes advantage of the fact that the index is sorted to speed up execution.
+ * It assumes that the index is sorted on the same field as the query, and performs binary
search
+ * on the field's doc values to find the documents at the lower and upper ends of the range.
+ *
+ * This optimized execution strategy can only be used if all of these conditions hold:
+ *   - The index is sorted, and its primary sort is on the same field as the query.
+ *   - The provided field has {@link SortedNumericDocValues}.
+ *   - The segments must have at most one field value per document (otherwise we cannot easily
+ *     determine the matching document IDs through a binary search).
+ */
+public final class IndexSortDocValuesRangeQuery extends Query {
+
+  private final String field;
+  private final long lowerValue;
+  private final long upperValue;
+
+  /**
+   * Creates a new {@link IndexSortDocValuesRangeQuery}.
+   *
+   * @param field The field name.
+   * @param lowerValue The lower end of the range (inclusive).
+   * @param upperValue The upper end of the range (inclusive).
+   */
+  public IndexSortDocValuesRangeQuery(String field,
+                                      long lowerValue,
+                                      long upperValue) {
+    this.field = field;
+    this.lowerValue = lowerValue;
+    this.upperValue = upperValue;
+  }
+
+  @Override
+  public Weight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost) {
+    return new ConstantScoreWeight(this, boost) {
+      @Override
+      public Scorer scorer(LeafReaderContext context) throws IOException {
+        LeafReader reader = context.reader();
+
+        Sort indexSort = reader.getMetaData().getSort();
+        if (indexSort == null || indexSort.getSort().length == 0) {
+          throw new IllegalArgumentException("To use IndexSortDocValuesRangeQuery, the index
must be sorted.");
+        }
+
+        SortField sortField = indexSort.getSort()[0];
+        if (sortField.getField().equals(field) == false) {
+          throw new IllegalArgumentException("To use IndexSortDocValuesRangeQuery, the index
must be sorted " +
+              "on the same field as the query field.");
+        }
+
+        SortedNumericDocValues sortedDocValues = reader.getSortedNumericDocValues(field);
+        NumericDocValues docValues = DocValues.unwrapSingleton(sortedDocValues);
+        if (docValues == null) {
+          throw new IllegalArgumentException("To use IndexSortDocValuesRangeQuery, the query
field must have " +
+              "SortedNumericDocValues and have at most one value per document.");
+        }
+
+        DocIdSetIterator disi = getDocIdSetIterator(lowerValue, upperValue,
+            sortField, context, docValues);
+        return new ConstantScoreScorer(this, score(), scoreMode, disi);
+      }
+
+      @Override
+      public boolean isCacheable(LeafReaderContext ctx) {
+        return DocValues.isCacheable(ctx, field);
+      }
+    };
+  }
+
+  /**
+   * Computes the document IDs that lie within the range [lowerValue, upperValue] by
+   * performing binary search on the field's doc values.
+   *
+   * Because doc values only allow forward iteration, we need to reload the field comparator
+   * every time the binary search accesses an earlier element.
+   */
+  private static DocIdSetIterator getDocIdSetIterator(long lowerValue,
+                                                      long upperValue,
+                                                      SortField sortField,
+                                                      LeafReaderContext context,
+                                                      DocIdSetIterator delegate) throws IOException
{
+    int maxDoc = context.reader().maxDoc();
+    if (maxDoc <= 0) {
+      return DocIdSetIterator.empty();
+    }
+
+    if (sortField.getReverse()) {
+      long temp = lowerValue;
+      lowerValue = upperValue;
+      upperValue = temp;
+    }
+
+    // Perform a binary search to find the first document with value >= lowerValue.
+    ValueComparator comparator = loadComparator(sortField, lowerValue, context);
+    int low = 0;
+    int high = maxDoc - 1;
+
+    while (low <= high) {
+      int mid = (low + high) >>> 1;
+      if (comparator.compare(mid) <= 0) {
+        high = mid - 1;
+        comparator = loadComparator(sortField, lowerValue, context);
 
 Review comment:
   @atris the issue description includes benchmarks on a realistic dataset with dense docvalues.
I share your concern that this reload may be expensive and plan to run more benchmarks with
different docvalues types (including sparse docvalues).

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