Remove leftover code from one shard by default

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.

Author: jasontedor

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 ClusterState execute(ClusterState currentState) throws Exception {
                     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 ClusterState execute(ClusterState currentState) throws Exception {
             }
         }
 
-        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 static boolean isSplitable(int source, int target) {
         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),