Plain highlighter should ignore parent/child queries.

The plain highligher fails when it tries to select the fragments based on a query containing either a `has_child` or `has_parent` query.

The plain highligher should just ignore parent/child queries as it makes no sense to highligh a parent match with a has_child as the child documents are not available at highlight time. Instead if child document should be highlighed inner hits should be used.

Parent/child queries already have no effect when the `fvh` or `postings` highligher is used. The test added in this commit verifies that.

Closes #14999

core/src/main/java/org/elasticsearch/index/query/HasChildQueryBuilder.java

@@ -352,7 +352,17 @@ public class HasChildQueryBuilder extends AbstractQueryBuilder<HasChildQueryBuil
                                     parentType, scoreMode, parentChildIndexFieldData, context.getSearchSimilarity());
     }
 
-    static final class LateParsingQuery extends Query {
+    /**
+     * A query that rewrites into another query using
+     * {@link JoinUtil#createJoinQuery(String, Query, Query, IndexSearcher, ScoreMode, MultiDocValues.OrdinalMap, int, int)}
+     * that executes the actual join.
+     *
+     * This query is exclusively used by the {@link HasChildQueryBuilder} and {@link HasParentQueryBuilder} to get access
+     * to the {@link DirectoryReader} used by the current search in order to retrieve the {@link MultiDocValues.OrdinalMap}.
+     * The {@link MultiDocValues.OrdinalMap} is required by {@link JoinUtil} to execute the join.
+     */
+    // TODO: Find a way to remove this query and let doToQuery(...) just return the query from JoinUtil.createJoinQuery(...)
+    public static final class LateParsingQuery extends Query {
 
         private final Query toQuery;
         private final Query innerQuery;

core/src/main/java/org/elasticsearch/search/highlight/CustomQueryScorer.java

@@ -27,6 +27,7 @@ import org.apache.lucene.search.highlight.WeightedSpanTermExtractor;
 import org.apache.lucene.spatial.geopoint.search.GeoPointInBBoxQuery;
 import org.elasticsearch.common.lucene.search.function.FiltersFunctionScoreQuery;
 import org.elasticsearch.common.lucene.search.function.FunctionScoreQuery;
+import org.elasticsearch.index.query.HasChildQueryBuilder;
 
 import java.io.IOException;
 import java.util.Map;
@@ -89,11 +90,16 @@ public final class CustomQueryScorer extends QueryScorer {
         }
 
         protected void extract(Query query, float boost, Map<String, WeightedSpanTerm> terms) throws IOException {
-            // skip all geo queries, see https://issues.apache.org/jira/browse/LUCENE-7293 and
+            if (query instanceof GeoPointInBBoxQuery) {
-            // https://github.com/elastic/elasticsearch/issues/17537
+                // skip all geo queries, see https://issues.apache.org/jira/browse/LUCENE-7293 and
-            if (query instanceof GeoPointInBBoxQuery == false) {
+                // https://github.com/elastic/elasticsearch/issues/17537
-                super.extract(query, boost, terms);
+                return;
+            } else if (query instanceof HasChildQueryBuilder.LateParsingQuery) {
+                // skip has_child or has_parent queries, see: https://github.com/elastic/elasticsearch/issues/14999
+                return;
             }
+
+            super.extract(query, boost, terms);
         }
     }
 }

core/src/test/java/org/elasticsearch/search/child/ChildQuerySearchIT.java

@@ -32,8 +32,12 @@ import org.elasticsearch.common.lucene.search.function.FiltersFunctionScoreQuery
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.index.IndexModule;
+import org.elasticsearch.index.query.BoolQueryBuilder;
 import org.elasticsearch.index.query.HasChildQueryBuilder;
+import org.elasticsearch.index.query.HasParentQueryBuilder;
 import org.elasticsearch.index.query.IdsQueryBuilder;
+import org.elasticsearch.index.query.MatchAllQueryBuilder;
+import org.elasticsearch.index.query.MatchQueryBuilder;
 import org.elasticsearch.index.query.QueryBuilder;
 import org.elasticsearch.index.query.QueryBuilders;
 import org.elasticsearch.index.query.functionscore.FunctionScoreQueryBuilder;
@@ -43,6 +47,8 @@ import org.elasticsearch.search.aggregations.bucket.filter.Filter;
 import org.elasticsearch.search.aggregations.bucket.global.Global;
 import org.elasticsearch.search.aggregations.bucket.terms.Terms;
 import org.elasticsearch.search.builder.SearchSourceBuilder;
+import org.elasticsearch.search.highlight.HighlightBuilder;
+import org.elasticsearch.search.highlight.HighlightField;
 import org.elasticsearch.search.sort.SortBuilders;
 import org.elasticsearch.search.sort.SortOrder;
 import org.elasticsearch.test.ESIntegTestCase;
@@ -1889,4 +1895,43 @@ public class ChildQuerySearchIT extends ESIntegTestCase {
                 QueryBuilders.hasChildQuery("child-type", new IdsQueryBuilder().addIds("child-id"), ScoreMode.None)).get();
         assertSearchHits(searchResponse, "parent-id");
     }
+
+    public void testHighlighersIgnoreParentChild() {
+        assertAcked(prepareCreate("test")
+                .addMapping("parent-type", "searchText", "type=text,term_vector=with_positions_offsets,index_options=offsets")
+                .addMapping("child-type", "_parent", "type=parent-type", "searchText",
+                        "type=text,term_vector=with_positions_offsets,index_options=offsets"));
+        client().prepareIndex("test", "parent-type", "parent-id").setSource("searchText", "quick brown fox").get();
+        client().prepareIndex("test", "child-type", "child-id").setParent("parent-id").setSource("searchText", "quick brown fox").get();
+        refresh();
+
+        String[] highlightTypes = new String[] {"plain", "fvh", "postings"};
+        for (String highlightType : highlightTypes) {
+            logger.info("Testing with highlight type [{}]", highlightType);
+            SearchResponse searchResponse = client().prepareSearch("test")
+                    .setQuery(new BoolQueryBuilder()
+                            .must(new MatchQueryBuilder("searchText", "fox"))
+                            .must(new HasChildQueryBuilder("child-type", new MatchAllQueryBuilder(), ScoreMode.None))
+                    )
+                    .highlighter(new HighlightBuilder().field(new HighlightBuilder.Field("searchText").highlighterType(highlightType)))
+                    .get();
+            assertHitCount(searchResponse, 1);
+            assertThat(searchResponse.getHits().getAt(0).id(), equalTo("parent-id"));
+            HighlightField highlightField = searchResponse.getHits().getAt(0).getHighlightFields().get("searchText");
+            assertThat(highlightField.getFragments()[0].string(), equalTo("quick brown <em>fox</em>"));
+
+            searchResponse = client().prepareSearch("test")
+                    .setQuery(new BoolQueryBuilder()
+                            .must(new MatchQueryBuilder("searchText", "fox"))
+                            .must(new HasParentQueryBuilder("parent-type", new MatchAllQueryBuilder(), false))
+                    )
+                    .highlighter(new HighlightBuilder().field(new HighlightBuilder.Field("searchText").highlighterType(highlightType)))
+                    .get();
+            assertHitCount(searchResponse, 1);
+            assertThat(searchResponse.getHits().getAt(0).id(), equalTo("child-id"));
+            highlightField = searchResponse.getHits().getAt(0).getHighlightFields().get("searchText");
+            assertThat(highlightField.getFragments()[0].string(), equalTo("quick brown <em>fox</em>"));
+        }
+    }
+
 }