Add clarifying comments.

Signed-off-by: currantw <[email protected]>

src/sqlodbc/opensearch_communication.cpp

@@ -572,10 +572,18 @@ bool OpenSearchCommunication::EstablishConnection() {
         InitializeConnection();
     }
 
+    // Set whether the connection is to OpenSearch serverless cluster.
+    // This can be specified explicitly via a configuration option, or
+    // determined by parsing the server URL.
     SetIsServerless();
+
+    // Set the SQL endpoint to connect to. If this is a serverless connection,
+    // the SQL endpoint can be determined directly; if not, the endpoint is
+    // determined by sending a request to OpenSearch, which may result in an
+    // error.
     SetSqlEndpoint();
 
-    if (sql_endpoint == SQL_ENDPOINT_ERROR) {
+    if (is_serverless && (sql_endpoint == SQL_ENDPOINT_ERROR)) {
         LogMsg(OPENSEARCH_ERROR, m_error_message.c_str());
         return false;
     }