Github user jpountz commented on a diff in the pull request:
https://github.com/apache/lucene-solr/pull/345#discussion_r179737753
--- Diff: lucene/core/src/java/org/apache/lucene/search/Matches.java ---
@@ -0,0 +1,116 @@
+/*
+ * 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 java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/**
+ * Reports the positions and optionally offsets of all matching terms in a
query
+ * for a single document
+ *
+ * To obtain a {@link MatchesIterator} for a particular field, call {@link
#getMatches(String)}
+ */
+public class Matches implements Iterable<String> {
+
+ /**
+ * Indicates a match with no term positions, for example on a Point or
DocValues field
+ */
+ public static final Matches MATCH_WITH_NO_TERMS = new
Matches(Collections.emptyMap());
+
+ private final Map<String, MatchesIterator> matches;
+
+ /**
+ * Create a simple {@link Matches} for a single field
+ */
+ public static Matches fromField(String field, MatchesIterator it) {
+ if (it == null) {
+ return null;
+ }
+ return new Matches(field, it);
+ }
+
+ /**
+ * Amalgamate a collection of {@link Matches} into a single object
+ */
+ public static Matches fromSubMatches(List<Matches> subMatches) throws
IOException {
+ if (subMatches == null || subMatches.size() == 0) {
+ return null;
+ }
+ subMatches = subMatches.stream().filter(m -> m !=
MATCH_WITH_NO_TERMS).collect(Collectors.toList());
+ if (subMatches.size() == 0) {
+ return MATCH_WITH_NO_TERMS;
+ }
+ if (subMatches.size() == 1) {
+ return subMatches.get(0);
+ }
+ Map<String, MatchesIterator> matches = new HashMap<>();
+ Set<String> allFields = new HashSet<>();
+ for (Matches m : subMatches) {
+ for (String field : m) {
+ allFields.add(field);
+ }
+ }
+ for (String field : allFields) {
+ List<MatchesIterator> mis = new ArrayList<>();
+ for (Matches m : subMatches) {
+ MatchesIterator mi = m.getMatches(field);
+ if (mi != null) {
+ mis.add(mi);
+ }
+ }
+ matches.put(field, DisjunctionMatchesIterator.fromSubIterators(mis));
+ }
+ return new Matches(matches);
+ }
+
+ /**
+ * Create a {@link Matches} from a map of fields to iterators
+ */
+ protected Matches(Map<String, MatchesIterator> matches) {
+ this.matches = matches;
+ }
+
+ private Matches(String field, MatchesIterator iterator) {
+ this.matches = Collections.singletonMap(field, iterator);
+ }
+
+ /**
+ * Returns a {@link MatchesIterator} over the matches for a single field,
+ * or {@code null} if there are no matches in that field.
+ *
+ * This method always returns the same iterator, so clients should only
+ * call it once per field
--- End diff --
I find these semantics a bit error-prone. I'd like something like `Fields`
where each call creates a new iterator better.
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