Fix: Pagination of index aliases is not supported

Signed-off-by: Aparajita Pandey <aparajita.pandey@uber.com>

Author: aparajita3

legacy/src/main/java/org/opensearch/sql/legacy/executor/format/SelectResultSet.java

@@ -26,8 +26,6 @@
 import java.util.stream.StreamSupport;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
-import org.opensearch.action.admin.indices.alias.get.GetAliasesRequest;
-import org.opensearch.action.admin.indices.alias.get.GetAliasesResponse;
 import org.opensearch.action.admin.indices.mapping.get.GetFieldMappingsRequest;
 import org.opensearch.action.admin.indices.mapping.get.GetFieldMappingsResponse;
 import org.opensearch.common.document.DocumentField;
@@ -163,11 +161,6 @@ private void populateResultSetFromDefaultCursor(DefaultCursor cursor) {
   private void loadFromEsState(Query query) {
     String indexName = fetchIndexName(query);
     String[] fieldNames = fetchFieldsAsArray(query);
-    GetAliasesResponse getAliasesResponse =
-        client.admin().indices().getAliases(new GetAliasesRequest(indexName)).actionGet();
-    if (getAliasesResponse != null && !getAliasesResponse.getAliases().isEmpty()) {
-      indexName = getAliasesResponse.getAliases().keySet().iterator().next();
-    }
     // Reset boolean in the case of JOIN query where multiple calls to loadFromEsState() are made
     selectAll = isSimpleQuerySelectAll(query) || isJoinQuerySelectAll(query, fieldNames);
 
@@ -180,11 +173,11 @@ private void loadFromEsState(Query query) {
         client.admin().indices().getFieldMappings(request).actionGet();
 
     Map<String, Map<String, FieldMappingMetadata>> mappings = response.mappings();
-    if (mappings.isEmpty() || !mappings.containsKey(indexName)) {
+    if (mappings.size() != 1) {
       throw new IllegalArgumentException(
           String.format("Index type %s does not exist", query.getFrom()));
     }
-    Map<String, FieldMappingMetadata> typeMappings = mappings.get(indexName);
+    Map<String, FieldMappingMetadata> typeMappings = mappings.values().iterator().next();
 
     this.indexName = this.indexName == null ? indexName : (this.indexName + "|" + indexName);
     this.columns.addAll(