Remove redundant ShardIterator interface

server/src/main/java/org/elasticsearch/action/get/TransportGetAction.java

@@ -28,7 +28,6 @@
 import org.elasticsearch.cluster.ClusterStateObserver;
 import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.cluster.node.DiscoveryNode;
-import org.elasticsearch.cluster.routing.PlainShardIterator;
 import org.elasticsearch.cluster.routing.ShardIterator;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -108,7 +107,7 @@ protected ShardIterator shards(ClusterState state, InternalRequest request) {
         if (iterator == null) {
             return null;
         }
-        return PlainShardIterator.allSearchableShards(iterator);
+        return ShardIterator.allSearchableShards(iterator);
     }
 
     @Override

server/src/main/java/org/elasticsearch/action/get/TransportShardMultiGetAction.java

@@ -28,7 +28,6 @@
 import org.elasticsearch.cluster.ClusterStateObserver;
 import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.cluster.node.DiscoveryNode;
-import org.elasticsearch.cluster.routing.PlainShardIterator;
 import org.elasticsearch.cluster.routing.ShardIterator;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -112,7 +111,7 @@ protected ShardIterator shards(ClusterState state, InternalRequest request) {
         if (iterator == null) {
             return null;
         }
-        return PlainShardIterator.allSearchableShards(iterator);
+        return ShardIterator.allSearchableShards(iterator);
     }
 
     @Override

server/src/main/java/org/elasticsearch/action/search/SearchShardIterator.java

@@ -10,7 +10,7 @@
 package org.elasticsearch.action.search;
 
 import org.elasticsearch.action.OriginalIndices;
-import org.elasticsearch.cluster.routing.PlainShardIterator;
+import org.elasticsearch.cluster.routing.ShardIterator;
 import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.common.util.Countable;
 import org.elasticsearch.common.util.PlainIterator;
@@ -24,7 +24,7 @@
 import java.util.Objects;
 
 /**
- * Extension of {@link PlainShardIterator} used in the search api, which also holds the {@link OriginalIndices}
+ * Extension of {@link ShardIterator} used in the search api, which also holds the {@link OriginalIndices}
  * of the search request (useful especially with cross-cluster search, as each cluster has its own set of original indices) as well as
  * the cluster alias.
  * @see OriginalIndices
@@ -42,7 +42,7 @@ public final class SearchShardIterator implements Comparable<SearchShardIterator
     private final PlainIterator<String> targetNodesIterator;
 
     /**
-     * Creates a {@link PlainShardIterator} instance that iterates over a subset of the given shards
+     * Creates a {@link ShardIterator} instance that iterates over a subset of the given shards
      * this the a given <code>shardId</code>.
      *
      * @param clusterAlias    the alias of the cluster where the shard is located
@@ -55,7 +55,7 @@ public SearchShardIterator(@Nullable String clusterAlias, ShardId shardId, List<
     }
 
     /**
-     * Creates a {@link PlainShardIterator} instance that iterates over a subset of the given shards
+     * Creates a {@link ShardIterator} instance that iterates over a subset of the given shards
      *
      * @param clusterAlias           the alias of the cluster where the shard is located
      * @param shardId                shard id of the group

server/src/main/java/org/elasticsearch/action/termvectors/TransportShardMultiTermsVectorAction.java

@@ -79,9 +79,11 @@ protected boolean resolveIndex(MultiTermVectorsShardRequest request) {
 
     @Override
     protected ShardIterator shards(ClusterState state, InternalRequest request) {
-        ShardIterator shards = clusterService.operationRouting()
-            .getShards(state, request.concreteIndex(), request.request().shardId(), request.request().preference());
-        return clusterService.operationRouting().useOnlyPromotableShardsForStateless(shards);
+        return clusterService.operationRouting()
+            .useOnlyPromotableShardsForStateless(
+                clusterService.operationRouting()
+                    .getShards(state, request.concreteIndex(), request.request().shardId(), request.request().preference())
+            );
     }
 
     @Override

server/src/main/java/org/elasticsearch/action/termvectors/TransportTermVectorsAction.java

@@ -60,7 +60,6 @@ public TransportTermVectorsAction(
 
     }
 
-    @Override
     protected ShardIterator shards(ClusterState state, InternalRequest request) {
         final var operationRouting = clusterService.operationRouting();
         if (request.request().doc() != null && request.request().routing() == null) {

server/src/main/java/org/elasticsearch/cluster/routing/GroupShardsIterator.java

@@ -16,9 +16,8 @@
 import java.util.List;
 
 /**
- * This class implements a compilation of {@link ShardIterator}s. Each {@link ShardIterator}
- * iterated by this {@link Iterable} represents a group of shards.
- * ShardsIterators are always returned in ascending order independently of their order at construction
+ * This class implements a compilation of shard iterators. Each shard iterator iterated by this {@link Iterable} represents a group of
+ * shards. ShardsIterators are always returned in ascending order independently of their order at construction
  * time. The incoming iterators are sorted to ensure consistent iteration behavior across Nodes / JVMs.
 */
 public final class GroupShardsIterator<ShardIt extends Comparable<ShardIt> & Countable> implements Iterable<ShardIt> {
@@ -27,7 +26,7 @@ public final class GroupShardsIterator<ShardIt extends Comparable<ShardIt> & Cou
 
     /**
      * Constructs a new sorted GroupShardsIterator from the given list. Items are sorted based on their natural ordering.
-     * @see PlainShardIterator#compareTo(ShardIterator)
+     * @see ShardIterator#compareTo(ShardIterator)
      */
     public static <ShardIt extends Comparable<ShardIt> & Countable> GroupShardsIterator<ShardIt> sortAndCreate(List<ShardIt> iterators) {
         CollectionUtil.timSort(iterators);

server/src/main/java/org/elasticsearch/cluster/routing/IndexShardRoutingTable.java

@@ -189,11 +189,11 @@ public List<ShardRouting> unpromotableShards() {
     }
 
     public ShardIterator shardsRandomIt() {
-        return new PlainShardIterator(shardId, shuffler.shuffle(Arrays.asList(shards)));
+        return new ShardIterator(shardId, shuffler.shuffle(Arrays.asList(shards)));
     }
 
     public ShardIterator shardsIt(int seed) {
-        return new PlainShardIterator(shardId, shuffler.shuffle(Arrays.asList(shards), seed));
+        return new ShardIterator(shardId, shuffler.shuffle(Arrays.asList(shards), seed));
     }
 
     /**
@@ -210,12 +210,12 @@ public ShardIterator activeInitializingShardsRandomIt() {
      */
     public ShardIterator activeInitializingShardsIt(int seed) {
         if (allInitializingShards.isEmpty()) {
-            return new PlainShardIterator(shardId, shuffler.shuffle(activeShards, seed));
+            return new ShardIterator(shardId, shuffler.shuffle(activeShards, seed));
         }
         ArrayList<ShardRouting> ordered = new ArrayList<>(activeShards.size() + allInitializingShards.size());
         ordered.addAll(shuffler.shuffle(activeShards, seed));
         ordered.addAll(allInitializingShards);
-        return new PlainShardIterator(shardId, ordered);
+        return new ShardIterator(shardId, ordered);
     }
 
     /**
@@ -229,18 +229,15 @@ public ShardIterator activeInitializingShardsRankedIt(
     ) {
         final int seed = shuffler.nextSeed();
         if (allInitializingShards.isEmpty()) {
-            return new PlainShardIterator(
-                shardId,
-                rankShardsAndUpdateStats(shuffler.shuffle(activeShards, seed), collector, nodeSearchCounts)
-            );
+            return new ShardIterator(shardId, rankShardsAndUpdateStats(shuffler.shuffle(activeShards, seed), collector, nodeSearchCounts));
         }
 
         ArrayList<ShardRouting> ordered = new ArrayList<>(activeShards.size() + allInitializingShards.size());
         List<ShardRouting> rankedActiveShards = rankShardsAndUpdateStats(shuffler.shuffle(activeShards, seed), collector, nodeSearchCounts);
         ordered.addAll(rankedActiveShards);
         List<ShardRouting> rankedInitializingShards = rankShardsAndUpdateStats(allInitializingShards, collector, nodeSearchCounts);
         ordered.addAll(rankedInitializingShards);
-        return new PlainShardIterator(shardId, ordered);
+        return new ShardIterator(shardId, ordered);
     }
 
     private static Set<String> getAllNodeIds(final List<ShardRouting> shards) {
@@ -398,9 +395,9 @@ public int compare(ShardRouting s1, ShardRouting s2) {
      */
     public ShardIterator primaryShardIt() {
         if (primary != null) {
-            return new PlainShardIterator(shardId, Collections.singletonList(primary));
+            return new ShardIterator(shardId, Collections.singletonList(primary));
         }
-        return new PlainShardIterator(shardId, Collections.emptyList());
+        return new ShardIterator(shardId, Collections.emptyList());
     }
 
     public ShardIterator onlyNodeActiveInitializingShardsIt(String nodeId) {
@@ -416,7 +413,7 @@ public ShardIterator onlyNodeActiveInitializingShardsIt(String nodeId) {
                 ordered.add(shardRouting);
             }
         }
-        return new PlainShardIterator(shardId, ordered);
+        return new ShardIterator(shardId, ordered);
     }
 
     public ShardIterator onlyNodeSelectorActiveInitializingShardsIt(String nodeAttributes, DiscoveryNodes discoveryNodes) {
@@ -451,7 +448,7 @@ public ShardIterator onlyNodeSelectorActiveInitializingShardsIt(String[] nodeAtt
             );
             throw new IllegalArgumentException(message);
         }
-        return new PlainShardIterator(shardId, ordered);
+        return new ShardIterator(shardId, ordered);
     }
 
     public ShardIterator preferNodeActiveInitializingShardsIt(Set<String> nodeIds) {
@@ -469,7 +466,7 @@ public ShardIterator preferNodeActiveInitializingShardsIt(Set<String> nodeIds) {
         if (allInitializingShards.isEmpty() == false) {
             preferred.addAll(allInitializingShards);
         }
-        return new PlainShardIterator(shardId, preferred);
+        return new ShardIterator(shardId, preferred);
     }
 
     @Override

server/src/main/java/org/elasticsearch/cluster/routing/OperationRouting.java

@@ -86,7 +86,7 @@ public ShardIterator useOnlyPromotableShardsForStateless(ShardIterator shards) {
         // If it is stateless, only route promotable shards. This is a temporary workaround until a more cohesive solution can be
         // implemented for search shards.
         if (isStateless && shards != null) {
-            return new PlainShardIterator(
+            return new ShardIterator(
                 shards.shardId(),
                 shards.getShardRoutings().stream().filter(ShardRouting::isPromotableToPrimary).collect(Collectors.toList())
             );
@@ -124,7 +124,7 @@ public GroupShardsIterator<ShardIterator> searchShards(
                 nodeCounts
             );
             if (iterator != null) {
-                set.add(PlainShardIterator.allSearchableShards(iterator));
+                set.add(ShardIterator.allSearchableShards(iterator));
             }
         }
         return GroupShardsIterator.sortAndCreate(new ArrayList<>(set));

server/src/main/java/org/elasticsearch/cluster/routing/RoutingTable.java

@@ -227,7 +227,7 @@ private GroupShardsIterator<ShardIterator> allSatisfyingPredicateShardsGrouped(
                     if (predicate.test(shardRouting)) {
                         set.add(shardRouting.shardsIt());
                     } else if (includeEmpty) { // we need this for counting properly, just make it an empty one
-                        set.add(new PlainShardIterator(shardRouting.shardId(), Collections.emptyList()));
+                        set.add(new ShardIterator(shardRouting.shardId(), Collections.emptyList()));
                     }
                 }
             }
@@ -299,7 +299,7 @@ public GroupShardsIterator<ShardIterator> activePrimaryShardsGrouped(String[] in
                 if (primary.active()) {
                     set.add(primary.shardsIt());
                 } else if (includeEmpty) { // we need this for counting properly, just make it an empty one
-                    set.add(new PlainShardIterator(primary.shardId(), Collections.emptyList()));
+                    set.add(new ShardIterator(primary.shardId(), Collections.emptyList()));
                 }
             }
         }

server/src/main/java/org/elasticsearch/cluster/routing/ShardIterator.java

@@ -11,19 +11,61 @@
 
 import org.elasticsearch.index.shard.ShardId;
 
+import java.util.ArrayList;
+import java.util.List;
+
 /**
- * Allows to iterate over a set of shard instances (routing) within a shard id group.
+ * The {@link ShardIterator} iterates shard copies for a given {@link ShardId shard id}
  */
-public interface ShardIterator extends ShardsIterator, Comparable<ShardIterator> {
+public class ShardIterator extends PlainShardsIterator implements Comparable<ShardIterator> {
 
-    /**
-     * The shard id this group relates to.
-     */
-    ShardId shardId();
+    private final ShardId shardId;
+
+    public static ShardIterator allSearchableShards(ShardIterator shardIterator) {
+        return new ShardIterator(shardIterator.shardId(), shardsThatCanHandleSearches(shardIterator));
+    }
+
+    private static List<ShardRouting> shardsThatCanHandleSearches(ShardIterator iterator) {
+        final List<ShardRouting> shardsThatCanHandleSearches = new ArrayList<>(iterator.size());
+        for (ShardRouting shardRouting : iterator) {
+            if (shardRouting.isSearchable()) {
+                shardsThatCanHandleSearches.add(shardRouting);
+            }
+        }
+        return shardsThatCanHandleSearches;
+    }
 
     /**
-     * Resets the iterator.
+     * Creates a {@link ShardIterator} instance that iterates over a subset of the given shards
+     * this the a given <code>shardId</code>.
+     *
+     * @param shardId shard id of the group
+     * @param shards  shards to iterate
      */
+    public ShardIterator(ShardId shardId, List<ShardRouting> shards) {
+        super(shards);
+        this.shardId = shardId;
+    }
+
+    public ShardId shardId() {
+        return this.shardId;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        ShardIterator that = (ShardIterator) o;
+        return shardId.equals(that.shardId());
+    }
+
+    @Override
+    public int hashCode() {
+        return shardId.hashCode();
+    }
+
     @Override
-    void reset();
+    public int compareTo(ShardIterator o) {
+        return shardId.compareTo(o.shardId());
+    }
 }

server/src/main/java/org/elasticsearch/cluster/routing/ShardRouting.java

@@ -329,7 +329,7 @@ public ShardId shardId() {
      * A shard iterator with just this shard in it.
      */
     public ShardIterator shardsIt() {
-        return new PlainShardIterator(shardId, List.of(this));
+        return new ShardIterator(shardId, List.of(this));
     }
 
     public ShardRouting(ShardId shardId, StreamInput in) throws IOException {