public long requestStatementId(IClientSession session) {
    long statementId = statementIdGenerator.incrementAndGet();
    session.addStatementId(statementId);
    return statementId;
  }
Check whether current user has logged in.

@return true: If logged in; false: If not logged in
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/protocol/session/SessionManager.java