Revert change that does not return all indices if a specific alias is requested via get alias api. (#28294)

Reopens #27763

Author: martijnvg

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

@@ -276,11 +276,8 @@ public ImmutableOpenMap<String, List<AliasMetaData>> findAliases(final String[]
             if (!filteredValues.isEmpty()) {
                 // Make the list order deterministic
                 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/test/java/org/elasticsearch/aliases/IndexAliasesIT.java

@@ -570,20 +570,24 @@ public void testIndicesGetAliases() throws Exception {
         logger.info("--> getting alias1");
         GetAliasesResponse getResponse = admin().indices().prepareGetAliases("alias1").get();
         assertThat(getResponse, notNullValue());
-        assertThat(getResponse.getAliases().size(), equalTo(1));
+        assertThat(getResponse.getAliases().size(), equalTo(5));
         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(1));
+        assertThat(getResponse.getAliases().size(), equalTo(5));
         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"));
@@ -595,6 +599,10 @@ 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));
 
@@ -679,12 +687,13 @@ 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(1));
+        assertThat(getResponse.getAliases().size(), equalTo(2));
         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));
@@ -693,13 +702,14 @@ 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(1));
+        assertThat(getResponse.getAliases().size(), equalTo(2));
         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));