Remove leftover code from one shard by default (#42374)

We had some logic to determine the number of shards, it was based on the
index version created. Now that master would only ever see index
versions created >= 7.0.0, this logic is no longer needed. This commit
removes this dead code.

server/src/main/java/org/elasticsearch/cluster/metadata/MetaDataCreateIndexService.java

@@ -20,7 +20,6 @@
 package org.elasticsearch.cluster.metadata;
 
 import com.carrotsearch.hppc.cursors.ObjectObjectCursor;
-
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.message.ParameterizedMessage;
@@ -386,8 +385,7 @@ public class MetaDataCreateIndexService {
                     indexSettingsBuilder.put(IndexMetaData.SETTING_INDEX_VERSION_CREATED.getKey(), createdVersion);
                 }
                 if (indexSettingsBuilder.get(SETTING_NUMBER_OF_SHARDS) == null) {
-                    final int numberOfShards = getNumberOfShards(indexSettingsBuilder);
-                    indexSettingsBuilder.put(SETTING_NUMBER_OF_SHARDS, settings.getAsInt(SETTING_NUMBER_OF_SHARDS, numberOfShards));
+                    indexSettingsBuilder.put(SETTING_NUMBER_OF_SHARDS, settings.getAsInt(SETTING_NUMBER_OF_SHARDS, 1));
                 }
                 if (indexSettingsBuilder.get(SETTING_NUMBER_OF_REPLICAS) == null) {
                     indexSettingsBuilder.put(SETTING_NUMBER_OF_REPLICAS, settings.getAsInt(SETTING_NUMBER_OF_REPLICAS, 1));
@@ -589,21 +587,6 @@ public class MetaDataCreateIndexService {
             }
         }
 
-        static int getNumberOfShards(final Settings.Builder indexSettingsBuilder) {
-            // TODO: this logic can be removed when the current major version is 8
-            // TODO: https://github.com/elastic/elasticsearch/issues/38556
-            // assert Version.CURRENT.major == 7;
-            final int numberOfShards;
-            final Version indexVersionCreated =
-                    Version.fromId(Integer.parseInt(indexSettingsBuilder.get(IndexMetaData.SETTING_INDEX_VERSION_CREATED.getKey())));
-            if (indexVersionCreated.before(Version.V_7_0_0)) {
-                numberOfShards = 5;
-            } else {
-                numberOfShards = 1;
-            }
-            return numberOfShards;
-        }
-
         @Override
         public void onFailure(String source, Exception e) {
             if (e instanceof ResourceAlreadyExistsException) {

server/src/test/java/org/elasticsearch/cluster/metadata/MetaDataCreateIndexServiceTests.java

@@ -99,14 +99,6 @@ public class MetaDataCreateIndexServiceTests extends ESTestCase {
         return source * x == target;
     }
 
-    public void testNumberOfShards() {
-        {
-            final Version versionCreated = VersionUtils.randomVersionBetween(random(), Version.V_7_0_0, Version.CURRENT);
-            final Settings.Builder indexSettingsBuilder = Settings.builder().put(SETTING_VERSION_CREATED, versionCreated);
-            assertThat(MetaDataCreateIndexService.IndexCreationTask.getNumberOfShards(indexSettingsBuilder), equalTo(1));
-        }
-    }
-
     public void testValidateShrinkIndex() {
         int numShards = randomIntBetween(2, 42);
         ClusterState state = createClusterState("source", numShards, randomIntBetween(0, 10),