Throw if two inner_hits have the same name

modules/parent-join/src/main/java/org/elasticsearch/join/query/HasChildQueryBuilder.java

@@ -460,9 +460,13 @@ protected QueryBuilder doRewrite(QueryRewriteContext queryShardContext) throws I
     @Override
     protected void extractInnerHitBuilders(Map<String, InnerHitContextBuilder> innerHits) {
         if (innerHitBuilder != null) {
+            String name = innerHitBuilder.getName() != null ? innerHitBuilder.getName() : type;
+            if (innerHits.containsKey(name)) {
+                throw new IllegalArgumentException("[inner_hits] already contains an entry for key [" + name + "]");
+            }
+
             Map<String, InnerHitContextBuilder> children = new HashMap<>();
             InnerHitContextBuilder.extractInnerHits(query, children);
-            String name = innerHitBuilder.getName() != null ? innerHitBuilder.getName() : type;
             InnerHitContextBuilder innerHitContextBuilder =
                 new ParentChildInnerHitContextBuilder(type, true, query, innerHitBuilder, children);
             innerHits.put(name, innerHitContextBuilder);

modules/parent-join/src/main/java/org/elasticsearch/join/query/HasParentQueryBuilder.java

@@ -285,9 +285,13 @@ protected QueryBuilder doRewrite(QueryRewriteContext queryShardContext) throws I
     @Override
     protected void extractInnerHitBuilders(Map<String, InnerHitContextBuilder> innerHits) {
         if (innerHitBuilder != null) {
+            String name = innerHitBuilder.getName() != null ? innerHitBuilder.getName() : type;
+            if (innerHits.containsKey(name)) {
+                throw new IllegalArgumentException("[inner_hits] already contains an entry for key [" + name + "]");
+            }
+
             Map<String, InnerHitContextBuilder> children = new HashMap<>();
             InnerHitContextBuilder.extractInnerHits(query, children);
-            String name = innerHitBuilder.getName() != null ? innerHitBuilder.getName() : type;
             InnerHitContextBuilder innerHitContextBuilder =
                 new ParentChildInnerHitContextBuilder(type, false, query, innerHitBuilder, children);
             innerHits.put(name, innerHitContextBuilder);

modules/parent-join/src/test/java/org/elasticsearch/join/query/HasChildQueryBuilderTests.java

@@ -367,4 +367,12 @@ public void testIgnoreUnmappedWithRewrite() throws IOException {
         assertThat(query, notNullValue());
         assertThat(query, instanceOf(MatchNoDocsQuery.class));
     }
+
+    public void testExtractInnerHitBuildersWithDuplicate() {
+        final HasChildQueryBuilder queryBuilder
+            = new HasChildQueryBuilder(CHILD_DOC, new WrapperQueryBuilder(new MatchAllQueryBuilder().toString()), ScoreMode.None);
+        queryBuilder.innerHit(new InnerHitBuilder("some_name"));
+        IllegalArgumentException e = expectThrows(IllegalArgumentException.class,
+            () -> InnerHitContextBuilder.extractInnerHits(queryBuilder, Collections.singletonMap("some_name", null)));
+    }
 }

modules/parent-join/src/test/java/org/elasticsearch/join/query/HasParentQueryBuilderTests.java

@@ -268,4 +268,12 @@ public void testIgnoreUnmappedWithRewrite() throws IOException {
         assertThat(query, notNullValue());
         assertThat(query, instanceOf(MatchNoDocsQuery.class));
     }
+
+    public void testExtractInnerHitBuildersWithDuplicate() {
+        final HasParentQueryBuilder queryBuilder
+            = new HasParentQueryBuilder(CHILD_DOC, new WrapperQueryBuilder(new MatchAllQueryBuilder().toString()), false);
+        queryBuilder.innerHit(new InnerHitBuilder("some_name"));
+        IllegalArgumentException e = expectThrows(IllegalArgumentException.class,
+            () -> InnerHitContextBuilder.extractInnerHits(queryBuilder, Collections.singletonMap("some_name", null)));
+    }
 }

server/src/main/java/org/elasticsearch/index/query/NestedQueryBuilder.java

@@ -317,10 +317,14 @@ protected QueryBuilder doRewrite(QueryRewriteContext queryRewriteContext) throws
     @Override
     public void extractInnerHitBuilders(Map<String, InnerHitContextBuilder> innerHits) {
         if (innerHitBuilder != null) {
+            String name = innerHitBuilder.getName() != null ? innerHitBuilder.getName() : path;
+            if (innerHits.containsKey(name)) {
+                throw new IllegalArgumentException("[inner_hits] already contains an entry for key [" + name + "]");
+            }
+
             Map<String, InnerHitContextBuilder> children = new HashMap<>();
             InnerHitContextBuilder.extractInnerHits(query, children);
             InnerHitContextBuilder innerHitContextBuilder = new NestedInnerHitContextBuilder(path, query, innerHitBuilder, children);
-            String name = innerHitBuilder.getName() != null ? innerHitBuilder.getName() : path;
             innerHits.put(name, innerHitContextBuilder);
         }
     }

server/src/test/java/org/elasticsearch/index/query/NestedQueryBuilderTests.java

@@ -41,6 +41,7 @@
 import org.hamcrest.Matchers;
 
 import java.io.IOException;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -354,4 +355,12 @@ public void testBuildIgnoreUnmappedNestQuery() throws Exception {
         nestedContextBuilder.build(searchContext, innerHitsContext);
         assertThat(innerHitsContext.getInnerHits().size(), Matchers.equalTo(0));
     }
+
+    public void testExtractInnerHitBuildersWithDuplicate() {
+        final NestedQueryBuilder queryBuilder
+            = new NestedQueryBuilder("path", new WrapperQueryBuilder(new MatchAllQueryBuilder().toString()), ScoreMode.None);
+        queryBuilder.innerHit(new InnerHitBuilder("some_name"));
+        IllegalArgumentException e = expectThrows(IllegalArgumentException.class,
+            () -> InnerHitContextBuilder.extractInnerHits(queryBuilder,Collections.singletonMap("some_name", null)));
+    }
 }

server/src/test/java/org/elasticsearch/search/aggregations/bucket/NestedIT.java

@@ -21,10 +21,13 @@
 import org.apache.lucene.search.join.ScoreMode;
 import org.elasticsearch.action.index.IndexRequestBuilder;
 import org.elasticsearch.action.search.SearchPhaseExecutionException;
+import org.elasticsearch.action.search.SearchRequestBuilder;
 import org.elasticsearch.action.search.SearchResponse;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentType;
+import org.elasticsearch.index.query.InnerHitBuilder;
+import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.search.aggregations.Aggregator.SubAggCollectionMode;
 import org.elasticsearch.search.aggregations.InternalAggregation;
 import org.elasticsearch.search.aggregations.bucket.filter.Filter;
@@ -46,6 +49,7 @@
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_NUMBER_OF_REPLICAS;
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_NUMBER_OF_SHARDS;
 import static org.elasticsearch.common.xcontent.XContentFactory.jsonBuilder;
+import static org.elasticsearch.index.query.QueryBuilders.boolQuery;
 import static org.elasticsearch.index.query.QueryBuilders.matchAllQuery;
 import static org.elasticsearch.index.query.QueryBuilders.nestedQuery;
 import static org.elasticsearch.index.query.QueryBuilders.termQuery;
@@ -57,6 +61,7 @@
 import static org.elasticsearch.search.aggregations.AggregationBuilders.sum;
 import static org.elasticsearch.search.aggregations.AggregationBuilders.terms;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
+import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertFailures;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertHitCount;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertNoFailures;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertSearchResponse;
@@ -674,4 +679,46 @@ public void testFilterAggInsideNestedAgg() throws Exception {
         numStringParams = bucket.getAggregations().get("num_string_params");
         assertThat(numStringParams.getDocCount(), equalTo(0L));
     }
+
+    public void testExtractInnerHitBuildersWithDuplicateHitName() throws Exception {
+        assertAcked(
+            prepareCreate("idxduplicatehitnames")
+                .setSettings(Settings.builder().put(SETTING_NUMBER_OF_SHARDS, 1).put(SETTING_NUMBER_OF_REPLICAS, 0))
+                .addMapping("product", "categories", "type=keyword", "name", "type=text", "property", "type=nested")
+        );
+        ensureGreen("idxduplicatehitnames");
+
+        SearchRequestBuilder searchRequestBuilder = client()
+            .prepareSearch("idxduplicatehitnames")
+            .setQuery(boolQuery()
+                .should(nestedQuery("property", termQuery("property.id", 1D), ScoreMode.None).innerHit(new InnerHitBuilder("ih1")))
+                .should(nestedQuery("property", termQuery("property.id", 1D), ScoreMode.None).innerHit(new InnerHitBuilder("ih2")))
+                .should(nestedQuery("property", termQuery("property.id", 1D), ScoreMode.None).innerHit(new InnerHitBuilder("ih1"))));
+
+        assertFailures(
+            searchRequestBuilder,
+            RestStatus.BAD_REQUEST,
+            containsString("[inner_hits] already contains an entry for key [ih1]"));
+    }
+
+    public void testExtractInnerHitBuildersWithDuplicatePath() throws Exception {
+        assertAcked(
+            prepareCreate("idxnullhitnames")
+                .setSettings(Settings.builder().put(SETTING_NUMBER_OF_SHARDS, 1).put(SETTING_NUMBER_OF_REPLICAS, 0))
+                .addMapping("product", "categories", "type=keyword", "name", "type=text", "property", "type=nested")
+        );
+        ensureGreen("idxnullhitnames");
+
+        SearchRequestBuilder searchRequestBuilder = client()
+            .prepareSearch("idxnullhitnames")
+            .setQuery(boolQuery()
+                .should(nestedQuery("property", termQuery("property.id", 1D), ScoreMode.None).innerHit(new InnerHitBuilder()))
+                .should(nestedQuery("property", termQuery("property.id", 1D), ScoreMode.None).innerHit(new InnerHitBuilder()))
+                .should(nestedQuery("property", termQuery("property.id", 1D), ScoreMode.None).innerHit(new InnerHitBuilder())));
+
+        assertFailures(
+            searchRequestBuilder,
+            RestStatus.BAD_REQUEST,
+            containsString("[inner_hits] already contains an entry for key [property]"));
+    }
 }