From 6a2eeedf37d1d217c50f18c55c5654fe8f68f140 Mon Sep 17 00:00:00 2001
From: Salvatore Campagna <salvatore.campagna@elastic.co>
Date: Fri, 12 Jul 2024 14:57:46 +0200
Subject: [PATCH 1/3] fix: do not include root level _type if not a metadata
 field

---
 .../rest-api-spec/test/20_parent_join.yml     | 53 +++++++++++++++++++
 .../search/fetch/subphase/FieldFetcher.java   |  6 +++
 2 files changed, 59 insertions(+)

diff --git a/modules/parent-join/src/yamlRestTest/resources/rest-api-spec/test/20_parent_join.yml b/modules/parent-join/src/yamlRestTest/resources/rest-api-spec/test/20_parent_join.yml
index daa9068162ffa..fd17d7df90870 100644
--- a/modules/parent-join/src/yamlRestTest/resources/rest-api-spec/test/20_parent_join.yml
+++ b/modules/parent-join/src/yamlRestTest/resources/rest-api-spec/test/20_parent_join.yml
@@ -161,3 +161,56 @@ teardown:
           mappings:
             properties:
               join_field: { "type": "join", "relations": { "parent": "child", "child": "grand_child" }, "fields": {"keyword": {"type": "keyword"}} }
+
+
+---
+"join on field named _type":
+  - requires:
+      cluster_features: [ "gte_v8.14.0" ]
+      reason: "deprecation added in 8.14"
+
+  - do:
+      indices.create:
+        index: type-join
+        body:
+          mappings:
+            properties:
+              text: { "type": "keyword" }
+              _type: { "type": "join", "relations": { "question": "answer" }}
+
+  - do:
+      bulk:
+        index: type-join
+        refresh: true
+        body:
+          - '{ "index": {"_id": "1"}}'
+          - '{ "text": "What species does chewbacca belong to", "_type": { "name": "question" }}'
+          - '{ "index": {"_id": "2"}}'
+          - '{ "text": "How did Yoda die?", "_type": { "name": "question" }}'
+
+  - do:
+      bulk:
+        index: type-join
+        refresh: true
+        body:
+          - '{ "index": {"_id": "3"}}'
+          - '{ "text": "Wookie", "_type": { "name": "answer", "parent": "1" }}'
+          - '{ "index": {"_id": "4"}}'
+          - '{ "text": "Old age", "_type": { "name": "answer", "parent": "2" }}'
+
+  - do:
+      search:
+        index: type-join
+        body: { query: { match_all: { } } }
+
+  - length: { hits.hits: 2 }
+
+  - match: { hits.hits.0._id: "1" }
+  - match: { hits.hits.0._type: null }
+  - match: { hits.hits.0._source._type.name: "question" }
+  - match: { hits.hits.0._source.text: "What species does chewbacca belong to"}
+
+  - match: { hits.hits.1._id: "2" }
+  - match: { hits.hits.1._type: null }
+  - match: { hits.hits.1._source._type.name: "question" }
+  - match: { hits.hits.1._source.text: "How did Yoda die?" }
diff --git a/server/src/main/java/org/elasticsearch/search/fetch/subphase/FieldFetcher.java b/server/src/main/java/org/elasticsearch/search/fetch/subphase/FieldFetcher.java
index fab794615a10d..9c198b6f44b92 100644
--- a/server/src/main/java/org/elasticsearch/search/fetch/subphase/FieldFetcher.java
+++ b/server/src/main/java/org/elasticsearch/search/fetch/subphase/FieldFetcher.java
@@ -11,6 +11,7 @@
 import org.apache.lucene.index.LeafReaderContext;
 import org.elasticsearch.common.document.DocumentField;
 import org.elasticsearch.common.regex.Regex;
+import org.elasticsearch.index.mapper.LegacyTypeFieldMapper;
 import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.index.mapper.NestedValueFetcher;
 import org.elasticsearch.index.mapper.ValueFetcher;
@@ -58,6 +59,11 @@ public static FieldFetcher create(SearchExecutionContext context, Collection<Fie
                 if (context.isMetadataField(field) && matchingPattern != null) {
                     continue;
                 }
+                // Include the `_type` field only if it is a metadata field .
+                // Above we already skip metadata fields in case of wildcard patterns.
+                if (context.isMetadataField(field) == false && LegacyTypeFieldMapper.NAME.equals(field)) {
+                    continue;
+                }
                 resolvedFields.add(new ResolvedField(field, matchingPattern, ft, fieldAndFormat.format));
             }
         }

From 2d5022cbaff9e12d13b4a8f56e3c91ddc1e99d47 Mon Sep 17 00:00:00 2001
From: Salvatore Campagna <salvatore.campagna@elastic.co>
Date: Fri, 12 Jul 2024 15:05:41 +0200
Subject: [PATCH 2/3] nit: missing question mark

---
 .../resources/rest-api-spec/test/20_parent_join.yml           | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/modules/parent-join/src/yamlRestTest/resources/rest-api-spec/test/20_parent_join.yml b/modules/parent-join/src/yamlRestTest/resources/rest-api-spec/test/20_parent_join.yml
index fd17d7df90870..99fdc658e42f2 100644
--- a/modules/parent-join/src/yamlRestTest/resources/rest-api-spec/test/20_parent_join.yml
+++ b/modules/parent-join/src/yamlRestTest/resources/rest-api-spec/test/20_parent_join.yml
@@ -184,7 +184,7 @@ teardown:
         refresh: true
         body:
           - '{ "index": {"_id": "1"}}'
-          - '{ "text": "What species does chewbacca belong to", "_type": { "name": "question" }}'
+          - '{ "text": "What species does chewbacca belong to?", "_type": { "name": "question" }}'
           - '{ "index": {"_id": "2"}}'
           - '{ "text": "How did Yoda die?", "_type": { "name": "question" }}'
 
@@ -208,7 +208,7 @@ teardown:
   - match: { hits.hits.0._id: "1" }
   - match: { hits.hits.0._type: null }
   - match: { hits.hits.0._source._type.name: "question" }
-  - match: { hits.hits.0._source.text: "What species does chewbacca belong to"}
+  - match: { hits.hits.0._source.text: "What species does chewbacca belong to?"}
 
   - match: { hits.hits.1._id: "2" }
   - match: { hits.hits.1._type: null }

From 7a1fba267a52ccff6b0d59140327ff6d0fa0d3e7 Mon Sep 17 00:00:00 2001
From: Salvatore Campagna
 <93581129+salvatore-campagna@users.noreply.github.com>
Date: Fri, 12 Jul 2024 19:33:47 +0200
Subject: [PATCH 3/3] Update docs/changelog/110825.yaml

---
 docs/changelog/110825.yaml | 6 ++++++
 1 file changed, 6 insertions(+)
 create mode 100644 docs/changelog/110825.yaml

diff --git a/docs/changelog/110825.yaml b/docs/changelog/110825.yaml
new file mode 100644
index 0000000000000..e4fb56a9a5e7d
--- /dev/null
+++ b/docs/changelog/110825.yaml
@@ -0,0 +1,6 @@
+pr: 110825
+summary: Do not include root level `_type` field if it is not a metadata field
+area: Mapping
+type: bug
+issues:
+ - 110438