protected String convertSchemaPattern(final String pattern) {
    if ((pattern == null) || pattern.isEmpty()) {
      return convertPattern("%", true);
    } else {
      return convertPattern(pattern, true);
    }
  }
Convert wildchars and escape sequence of schema pattern from JDBC format to datanucleous/regex
The schema pattern treats empty string also as wildchar
service/src/java/org/apache/hive/service/cli/operation/MetadataOperation.java