Remove the getConcreteIndexAndAliasMetadatas() method from IndexAbstraction.Alias class (#66165)

This change is part of series of changes to clean up the usage `IndexAbstraction.Alias` in the codebase,
so that it is no longer needed to cast to `IndexAbstraction.Alias` and just use the methods on the `IndexAbstraction`
interface. This should help adding data stream aliases, so that `IndexAbstraction` instances of type `ALIAS` can
also be data stream aliases.

Relates to #66163

Author: martijnvg

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

@@ -20,9 +20,7 @@
 
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Strings;
-import org.elasticsearch.common.collect.Tuple;
 
-import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -221,7 +219,6 @@ public List<IndexMetadata> getIndices() {
             return referenceIndexMetadatas;
         }
 
-
         @Nullable
         public IndexMetadata getWriteIndex() {
             return writeIndex;
@@ -243,30 +240,6 @@ public boolean isSystem() {
             return referenceIndexMetadatas.stream().allMatch(IndexMetadata::isSystem);
         }
 
-        /**
-         * Returns the unique alias metadata per concrete index.
-         * <p>
-         * (note that although alias can point to the same concrete indices, each alias reference may have its own routing
-         * and filters)
-         */
-        public Iterable<Tuple<String, AliasMetadata>> getConcreteIndexAndAliasMetadatas() {
-            return () -> new Iterator<>() {
-
-                int index = 0;
-
-                @Override
-                public boolean hasNext() {
-                    return index < referenceIndexMetadatas.size();
-                }
-
-                @Override
-                public Tuple<String, AliasMetadata> next() {
-                    IndexMetadata indexMetadata = referenceIndexMetadatas.get(index++);
-                    return new Tuple<>(indexMetadata.getIndex().getName(), indexMetadata.getAliases().get(aliasName));
-                }
-            };
-        }
-
         public AliasMetadata getFirstAliasMetadata() {
             return referenceIndexMetadatas.get(0).getAliases().get(aliasName);
         }

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

@@ -28,7 +28,6 @@
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.collect.ImmutableOpenMap;
-import org.elasticsearch.common.collect.Tuple;
 import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.regex.Regex;
 import org.elasticsearch.common.time.DateFormatter;
@@ -563,10 +562,9 @@ public Map<String, Set<String>> resolveSearchRouting(ClusterState state, @Nullab
         for (String expression : resolvedExpressions) {
             IndexAbstraction indexAbstraction = state.metadata().getIndicesLookup().get(expression);
             if (indexAbstraction != null && indexAbstraction.getType() == IndexAbstraction.Type.ALIAS) {
-                IndexAbstraction.Alias alias = (IndexAbstraction.Alias) indexAbstraction;
-                for (Tuple<String, AliasMetadata> item : alias.getConcreteIndexAndAliasMetadatas()) {
-                    String concreteIndex = item.v1();
-                    AliasMetadata aliasMetadata = item.v2();
+                for (IndexMetadata index : indexAbstraction.getIndices()) {
+                    String concreteIndex = index.getIndex().getName();
+                    AliasMetadata aliasMetadata = index.getAliases().get(indexAbstraction.getName());
                     if (!norouting.contains(concreteIndex)) {
                         if (!aliasMetadata.searchRoutingValues().isEmpty()) {
                             // Routing alias