From c9696840671840c61c9615a410891254a456f639 Mon Sep 17 00:00:00 2001
From: Yannick Welsch <yannick@welsch.lu>
Date: Tue, 10 May 2022 10:24:01 +0200
Subject: [PATCH] Disable get API on legacy indices

---
 .../java/org/elasticsearch/index/shard/IndexShard.java    | 3 +++
 .../org/elasticsearch/oldrepos/OldRepositoryAccessIT.java | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/server/src/main/java/org/elasticsearch/index/shard/IndexShard.java b/server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
index 4764dc5e78479..4fb9b0a383bc1 100644
--- a/server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
+++ b/server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
@@ -1185,6 +1185,9 @@ public Engine.GetResult get(Engine.Get get) {
         if (mappingLookup.hasMappings() == false) {
             return GetResult.NOT_EXISTS;
         }
+        if (indexSettings.getIndexVersionCreated().isLegacyIndexVersion()) {
+            throw new IllegalStateException("get operations not allowed on a legacy index");
+        }
         return getEngine().get(get, mappingLookup, mapperService.documentParser(), this::wrapSearcher);
     }
 
diff --git a/x-pack/qa/repository-old-versions/src/test/java/org/elasticsearch/oldrepos/OldRepositoryAccessIT.java b/x-pack/qa/repository-old-versions/src/test/java/org/elasticsearch/oldrepos/OldRepositoryAccessIT.java
index 899b9ddfa8683..bd584302da02f 100644
--- a/x-pack/qa/repository-old-versions/src/test/java/org/elasticsearch/oldrepos/OldRepositoryAccessIT.java
+++ b/x-pack/qa/repository-old-versions/src/test/java/org/elasticsearch/oldrepos/OldRepositoryAccessIT.java
@@ -16,6 +16,7 @@
 import org.elasticsearch.client.Request;
 import org.elasticsearch.client.RequestOptions;
 import org.elasticsearch.client.Response;
+import org.elasticsearch.client.ResponseException;
 import org.elasticsearch.client.RestClient;
 import org.elasticsearch.client.RestHighLevelClient;
 import org.elasticsearch.client.core.ShardsAcknowledgedResponse;
@@ -49,6 +50,7 @@
 import java.util.stream.Collectors;
 
 import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThan;
@@ -455,6 +457,12 @@ private void assertDocs(
                     assertEquals(randomType, typeField.getValue());
                 }
             }
+
+            assertThat(
+                expectThrows(ResponseException.class, () -> client().performRequest(new Request("GET", "/" + index + "/_doc/" + id)))
+                    .getMessage(),
+                containsString("get operations not allowed on a legacy index")
+            );
         }
     }