### Elasticsearch Version

8.6.0

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

docker-image = docker.elastic.co/elasticsearch/elasticsearch:8.6

### Problem Description

We are trying to migrate from Elasticsearch 6.7.1 to Elasticsearch 8.6.0.

With the same document we always get IndexOutOfBoundsException while trying to fetch innerhits in Elasticsearch 8.6.0. Everything works fine in Elasticsearch 6.7.1.


### Steps to Reproduce

[elasticsearch_6.7.1 (1).txt](https://github.com/elastic/elasticsearch/files/10466823/elasticsearch_6.7.1.1.txt)
[elasticsearch_8.6.0.txt](https://github.com/elastic/elasticsearch/files/10466824/elasticsearch_8.6.0.txt)


### Logs (if relevant)

`{"@timestamp":"2023-01-20T13:39:21.170Z", "log.level": "WARN", "message":"path: /test/_search, params: {index=test}", "ecs.version": "1.2.0","service.name":"ES_ECS","event.dataset":"elasticsearch.server","process.thread.name":"elasticsearch[es01][search][T#10]","log.logger":"rest.suppressed","elasticsearch.cluster.uuid":"T3_Kb_fZTOORKN7Bn5jz2g","elasticsearch.node.id":"fESFHfZ-RxuDaPIIKhOoNA","elasticsearch.node.name":"es01","elasticsearch.cluster.name":"es_alex","error.type":"org.elasticsearch.action.search.SearchPhaseExecutionException","error.message":"all shards failed","error.stack_trace":"Failed to execute phase [query], all shards failed; shardFailures {[fESFHfZ-RxuDaPIIKhOoNA][test][0]: org.elasticsearch.transport.RemoteTransportException: [es01][172.27.0.2:9300][indices:data/read/search[phase/query]]\nCaused by: org.elasticsearch.search.fetch.FetchPhaseExecutionException: Fetch Failed [Error running fetch phase for doc [73]]\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.buildSearchHits(FetchPhase.java:181)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.execute(FetchPhase.java:93)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.SearchService.executeFetchPhase(SearchService.java:659)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.SearchService.executeQueryPhase(SearchService.java:634)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.SearchService.lambda$executeQueryPhase$2(SearchService.java:489)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.ActionRunnable.lambda$supply$0(ActionRunnable.java:47)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.ActionRunnable$2.doRun(ActionRunnable.java:62)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.common.util.concurrent.TimedRunnable.doRun(TimedRunnable.java:33)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:769)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26)\n\tat java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)\n\tat java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)\n\tat java.base/java.lang.Thread.run(Thread.java:833)\nCaused by: org.elasticsearch.search.fetch.FetchPhaseExecutionException: Fetch Failed [Error running fetch phase for doc [43]]\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.buildSearchHits(FetchPhase.java:181)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.execute(FetchPhase.java:93)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.subphase.InnerHitsPhase.hitExecute(InnerHitsPhase.java:76)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.subphase.InnerHitsPhase$1.process(InnerHitsPhase.java:52)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.buildSearchHits(FetchPhase.java:177)\n\t... 13 more\nCaused by: java.lang.IndexOutOfBoundsException: Index: 43, Size: 1\n\tat java.base/java.util.Collections$SingletonList.get(Collections.java:4959)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.prepareNestedHitContext(FetchPhase.java:466)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.prepareHitContext(FetchPhase.java:312)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.buildSearchHits(FetchPhase.java:165)\n\t... 17 more\n}\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.search.AbstractSearchAsyncAction.onPhaseFailure(AbstractSearchAsyncAction.java:728)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.search.AbstractSearchAsyncAction.executeNextPhase(AbstractSearchAsyncAction.java:418)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.search.AbstractSearchAsyncAction.onPhaseDone(AbstractSearchAsyncAction.java:760)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.search.AbstractSearchAsyncAction.onShardFailure(AbstractSearchAsyncAction.java:512)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.search.AbstractSearchAsyncAction$1.onFailure(AbstractSearchAsyncAction.java:349)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.ActionListener$Delegating.onFailure(ActionListener.java:92)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.ActionListenerResponseHandler.handleException(ActionListenerResponseHandler.java:48)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.search.SearchTransportService$ConnectionCountingHandler.handleException(SearchTransportService.java:642)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.transport.TransportService$UnregisterChildTransportResponseHandler.handleException(TransportService.java:1650)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.transport.TransportService$ContextRestoreResponseHandler.handleException(TransportService.java:1390)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.transport.TransportService$DirectResponseChannel.processException(TransportService.java:1512)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.transport.TransportService$DirectResponseChannel.sendResponse(TransportService.java:1487)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.transport.TaskTransportChannel.sendResponse(TaskTransportChannel.java:50)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.support.ChannelActionListener.onFailure(ChannelActionListener.java:48)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.ActionRunnable.onFailure(ActionRunnable.java:77)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:28)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.common.util.concurrent.TimedRunnable.doRun(TimedRunnable.java:33)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:769)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26)\n\tat java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)\n\tat java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)\n\tat java.base/java.lang.Thread.run(Thread.java:833)\nCaused by: org.elasticsearch.ElasticsearchException$1: Index: 43, Size: 1\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.ElasticsearchException.guessRootCauses(ElasticsearchException.java:638)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.search.AbstractSearchAsyncAction.executeNextPhase(AbstractSearchAsyncAction.java:416)\n\t... 20 more\nCaused by: java.lang.IndexOutOfBoundsException: Index: 43, Size: 1\n\tat java.base/java.util.Collections$SingletonList.get(Collections.java:4959)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.prepareNestedHitContext(FetchPhase.java:466)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.prepareHitContext(FetchPhase.java:312)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.buildSearchHits(FetchPhase.java:165)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.execute(FetchPhase.java:93)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.subphase.InnerHitsPhase.hitExecute(InnerHitsPhase.java:76)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.subphase.InnerHitsPhase$1.process(InnerHitsPhase.java:52)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.buildSearchHits(FetchPhase.java:177)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.fetch.FetchPhase.execute(FetchPhase.java:93)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.SearchService.executeFetchPhase(SearchService.java:659)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.SearchService.executeQueryPhase(SearchService.java:634)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.search.SearchService.lambda$executeQueryPhase$2(SearchService.java:489)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.ActionRunnable.lambda$supply$0(ActionRunnable.java:47)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.action.ActionRunnable$2.doRun(ActionRunnable.java:62)\n\tat org.elasticsearch.server@8.4.3/org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26)\n\t... 6 more\n"}`
server/src/main/java/org/elasticsearch/search/SearchHit.java
* In the case of mappings with multiple levels of nested object fields
         */
        public NestedIdentity getChild() {
            return child;
        }
        /**
         * Extracts the part of the root source that applies to this particular NestedIdentity, while
         * preserving the enclosing path structure.
         *
         * For a root document that looks like this:
         * { "children" :
         *    [
         *      { "grandchildren" : [ { "field" : "value1" }, { "field" : "value2" } ] },
         *      { "grandchildren" : [ { "field" : "value3" }, { "field" : "value4" } ] }
         *   ]
         * }
         *
         * Extracting the NestedIdentity of the first child and second grandchild results in a source that looks like this:
         * { "children" : { "grandchildren" : { "field" : "value2" } } }
         *
         * If the relevant child source object does not exist in the root, then we return {@link Source#empty(XContentType)}
         */
        @SuppressWarnings("unchecked")
        public Source extractSource(Source root) {
            
            
            
            
            Map<String, Object> rootSourceAsMap = root.source();
            Map<String, Object> nestedSourceAsMap = new HashMap<>();