Do not return all indices if a specific alias is requested via get aliases api.

If a get alias api call requests a specific alias pattern then
indices not having any matching aliases should not be included in the response.

Closes #27763

Author: martijnvg

server/src/main/java/org/elasticsearch/action/admin/indices/alias/get/TransportGetAliasesAction.java

@@ -62,8 +62,7 @@ protected GetAliasesResponse newResponse() {
     @Override
     protected void masterOperation(GetAliasesRequest request, ClusterState state, ActionListener<GetAliasesResponse> listener) {
         String[] concreteIndices = indexNameExpressionResolver.concreteIndexNames(state, request);
-        @SuppressWarnings("unchecked")
-                ImmutableOpenMap<String, List<AliasMetaData>> result = (ImmutableOpenMap) state.metaData().findAliases(request.aliases(), concreteIndices);
+        ImmutableOpenMap<String, List<AliasMetaData>> result = state.metaData().findAliases(request.aliases(), concreteIndices);
         listener.onResponse(new GetAliasesResponse(result));
     }
 

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

@@ -275,14 +275,12 @@ public ImmutableOpenMap<String, List<AliasMetaData>> findAliases(final String[]
 
             if (!filteredValues.isEmpty()) {
                 // Make the list order deterministic
-                CollectionUtil.timSort(filteredValues, new Comparator<AliasMetaData>() {
-                    @Override
-                    public int compare(AliasMetaData o1, AliasMetaData o2) {
-                        return o1.alias().compareTo(o2.alias());
-                    }
-                });
+                CollectionUtil.timSort(filteredValues, Comparator.comparing(AliasMetaData::alias));
+                mapBuilder.put(index, Collections.unmodifiableList(filteredValues));
+            } else if (matchAllAliases) {
+                // in case all aliases are requested then it is desired to return the concrete index with no aliases (#25114):
+                mapBuilder.put(index, Collections.emptyList());
             }
-            mapBuilder.put(index, Collections.unmodifiableList(filteredValues));
         }
         return mapBuilder.build();
     }

server/src/main/java/org/elasticsearch/rest/action/admin/indices/RestGetAliasesAction.java

@@ -19,7 +19,6 @@
 
 package org.elasticsearch.rest.action.admin.indices;
 
-import com.carrotsearch.hppc.cursors.ObjectCursor;
 import com.carrotsearch.hppc.cursors.ObjectObjectCursor;
 import org.elasticsearch.action.admin.indices.alias.get.GetAliasesRequest;
 import org.elasticsearch.action.admin.indices.alias.get.GetAliasesResponse;

server/src/test/java/org/elasticsearch/aliases/IndexAliasesIT.java

@@ -570,24 +570,20 @@ public void testIndicesGetAliases() throws Exception {
         logger.info("--> getting alias1");
         GetAliasesResponse getResponse = admin().indices().prepareGetAliases("alias1").get();
         assertThat(getResponse, notNullValue());
-        assertThat(getResponse.getAliases().size(), equalTo(5));
+        assertThat(getResponse.getAliases().size(), equalTo(1));
         assertThat(getResponse.getAliases().get("foobar").size(), equalTo(1));
         assertThat(getResponse.getAliases().get("foobar").get(0), notNullValue());
         assertThat(getResponse.getAliases().get("foobar").get(0).alias(), equalTo("alias1"));
         assertThat(getResponse.getAliases().get("foobar").get(0).getFilter(), nullValue());
         assertThat(getResponse.getAliases().get("foobar").get(0).getIndexRouting(), nullValue());
         assertThat(getResponse.getAliases().get("foobar").get(0).getSearchRouting(), nullValue());
-        assertTrue(getResponse.getAliases().get("test").isEmpty());
-        assertTrue(getResponse.getAliases().get("test123").isEmpty());
-        assertTrue(getResponse.getAliases().get("foobarbaz").isEmpty());
-        assertTrue(getResponse.getAliases().get("bazbar").isEmpty());
         AliasesExistResponse existsResponse = admin().indices().prepareAliasesExist("alias1").get();
         assertThat(existsResponse.exists(), equalTo(true));
 
         logger.info("--> getting all aliases that start with alias*");
         getResponse = admin().indices().prepareGetAliases("alias*").get();
         assertThat(getResponse, notNullValue());
-        assertThat(getResponse.getAliases().size(), equalTo(5));
+        assertThat(getResponse.getAliases().size(), equalTo(1));
         assertThat(getResponse.getAliases().get("foobar").size(), equalTo(2));
         assertThat(getResponse.getAliases().get("foobar").get(0), notNullValue());
         assertThat(getResponse.getAliases().get("foobar").get(0).alias(), equalTo("alias1"));
@@ -599,10 +595,6 @@ public void testIndicesGetAliases() throws Exception {
         assertThat(getResponse.getAliases().get("foobar").get(1).getFilter(), nullValue());
         assertThat(getResponse.getAliases().get("foobar").get(1).getIndexRouting(), nullValue());
         assertThat(getResponse.getAliases().get("foobar").get(1).getSearchRouting(), nullValue());
-        assertTrue(getResponse.getAliases().get("test").isEmpty());
-        assertTrue(getResponse.getAliases().get("test123").isEmpty());
-        assertTrue(getResponse.getAliases().get("foobarbaz").isEmpty());
-        assertTrue(getResponse.getAliases().get("bazbar").isEmpty());
         existsResponse = admin().indices().prepareAliasesExist("alias*").get();
         assertThat(existsResponse.exists(), equalTo(true));
 
@@ -687,13 +679,12 @@ public void testIndicesGetAliases() throws Exception {
         logger.info("--> getting f* for index *bar");
         getResponse = admin().indices().prepareGetAliases("f*").addIndices("*bar").get();
         assertThat(getResponse, notNullValue());
-        assertThat(getResponse.getAliases().size(), equalTo(2));
+        assertThat(getResponse.getAliases().size(), equalTo(1));
         assertThat(getResponse.getAliases().get("foobar").get(0), notNullValue());
         assertThat(getResponse.getAliases().get("foobar").get(0).alias(), equalTo("foo"));
         assertThat(getResponse.getAliases().get("foobar").get(0).getFilter(), nullValue());
         assertThat(getResponse.getAliases().get("foobar").get(0).getIndexRouting(), nullValue());
         assertThat(getResponse.getAliases().get("foobar").get(0).getSearchRouting(), nullValue());
-        assertTrue(getResponse.getAliases().get("bazbar").isEmpty());
         existsResponse = admin().indices().prepareAliasesExist("f*")
                 .addIndices("*bar").get();
         assertThat(existsResponse.exists(), equalTo(true));
@@ -702,14 +693,13 @@ public void testIndicesGetAliases() throws Exception {
         logger.info("--> getting f* for index *bac");
         getResponse = admin().indices().prepareGetAliases("foo").addIndices("*bac").get();
         assertThat(getResponse, notNullValue());
-        assertThat(getResponse.getAliases().size(), equalTo(2));
+        assertThat(getResponse.getAliases().size(), equalTo(1));
         assertThat(getResponse.getAliases().get("foobar").size(), equalTo(1));
         assertThat(getResponse.getAliases().get("foobar").get(0), notNullValue());
         assertThat(getResponse.getAliases().get("foobar").get(0).alias(), equalTo("foo"));
         assertThat(getResponse.getAliases().get("foobar").get(0).getFilter(), nullValue());
         assertThat(getResponse.getAliases().get("foobar").get(0).getIndexRouting(), nullValue());
         assertThat(getResponse.getAliases().get("foobar").get(0).getSearchRouting(), nullValue());
-        assertTrue(getResponse.getAliases().get("bazbar").isEmpty());
         existsResponse = admin().indices().prepareAliasesExist("foo")
                 .addIndices("*bac").get();
         assertThat(existsResponse.exists(), equalTo(true));