[Backport 2.x] Revert "Removing unused fetch sub phase processor init…

…ialization during fetch… (opensearch-project#12503)" (opensearch-project#13491)

* Revert "Removing unused fetch sub phase processor initialization during fetch… (opensearch-project#12503)" (opensearch-project#13486)

This reverts commit da5b205.

Signed-off-by: Andriy Redko <[email protected]>
(cherry picked from commit 5133e5f)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Signed-off-by: Andriy Redko <[email protected]>

* Update 400_inner_hits.yml

Signed-off-by: Andriy Redko <[email protected]>

---------

Signed-off-by: Andriy Redko <[email protected]>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Andriy Redko <[email protected]>

CHANGELOG.md

@@ -71,6 +71,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Refactoring globMatch using simpleMatchWithNormalizedStrings from Regex ([#13104](https://github.com/opensearch-project/OpenSearch/pull/13104))
 - [BWC and API enforcement] Reconsider the breaking changes check policy to detect breaking changes against released versions ([#13292](https://github.com/opensearch-project/OpenSearch/pull/13292))
 - Switch to macos-13 runner for precommit and assemble github actions due to macos-latest is now arm64 ([#13412](https://github.com/opensearch-project/OpenSearch/pull/13412))
+- [Revert] Prevent unnecessary fetch sub phase processor initialization during fetch phase execution ([#12503](https://github.com/opensearch-project/OpenSearch/pull/12503))
 
 ### Deprecated
 

rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/400_inner_hits.yml

@@ -0,0 +1,68 @@
+setup:
+  - do:
+      indices.create:
+          index: test_1
+          body:
+            settings:
+              number_of_replicas: 0
+            mappings:
+              properties:
+                list_id:
+                  type: integer
+                names:
+                  type: nested
+                  properties:
+                    full_name:
+                      type: text
+
+  - do:
+       bulk:
+         refresh: true
+         body:
+           - index:
+               _index: test_1
+               _id:    1
+           - list_id: 1
+             names:
+               - full_name: John Doe
+               - full_name: John Micheal Doe
+           - index:
+               _index: test_1
+               _id:    2
+           - list_id: 2
+             names:
+               - full_name: Jane Doe
+               - full_name: Jane Michelle Doe
+
+---
+"Include inner hits in top hits":
+  - skip:
+      version: " - 2.13.99"
+      reason: "the regression was fixed in 2.14.0"
+  - do:
+      search:
+        rest_total_hits_as_int: true
+        body:
+          query:
+            nested:
+              path: names
+              query:
+                match:
+                  names.full_name: Doe
+              inner_hits: { }
+          size: 0
+          aggs:
+            lists:
+              terms:
+                field: list_id
+              aggs:
+                top_result:
+                  top_hits:
+                    size: 10
+
+  - length: { hits.hits: 0 }
+  - length: { aggregations.lists.buckets: 2 }
+  - length: { aggregations.lists.buckets.0.top_result.hits.hits: 1 }
+  - length: { aggregations.lists.buckets.0.top_result.hits.hits.0.inner_hits.names.hits.hits: 2 }
+  - length: { aggregations.lists.buckets.1.top_result.hits.hits: 1 }
+  - length: { aggregations.lists.buckets.1.top_result.hits.hits.0.inner_hits.names.hits.hits: 2 }

server/src/main/java/org/opensearch/search/fetch/FetchContext.java

@@ -192,10 +192,6 @@ public boolean includeNamedQueriesScore() {
         return searchContext.includeNamedQueriesScore();
     }
 
-    public boolean hasInnerHits() {
-        return searchContext.hasInnerHits();
-    }
-
     /**
      * Configuration for returning inner hits
      */
@@ -217,10 +213,6 @@ public FetchFieldsContext fetchFieldsContext() {
         return searchContext.fetchFieldsContext();
     }
 
-    public boolean hasScriptFields() {
-        return searchContext.hasScriptFields();
-    }
-
     /**
      * Configuration for script fields
      */

server/src/main/java/org/opensearch/search/fetch/subphase/InnerHitsContext.java

@@ -119,11 +119,6 @@ public String getName() {
             return name;
         }
 
-        @Override
-        public boolean hasInnerHits() {
-            return childInnerHits != null;
-        }
-
         @Override
         public InnerHitsContext innerHits() {
             return childInnerHits;

server/src/main/java/org/opensearch/search/fetch/subphase/InnerHitsPhase.java

@@ -64,7 +64,7 @@ public InnerHitsPhase(FetchPhase fetchPhase) {
 
     @Override
     public FetchSubPhaseProcessor getProcessor(FetchContext searchContext) {
-        if (searchContext.hasInnerHits() == false) {
+        if (searchContext.innerHits() == null) {
             return null;
         }
         Map<String, InnerHitsContext.InnerHitSubContext> innerHits = searchContext.innerHits().getInnerHits();

server/src/main/java/org/opensearch/search/fetch/subphase/ScriptFieldsPhase.java

@@ -54,7 +54,7 @@ public final class ScriptFieldsPhase implements FetchSubPhase {
 
     @Override
     public FetchSubPhaseProcessor getProcessor(FetchContext context) {
-        if (context.hasScriptFields() == false) {
+        if (context.scriptFields() == null) {
             return null;
         }
         List<ScriptFieldsContext.ScriptField> scriptFields = context.scriptFields().fields();