private OperationQuota checkQuota(String userName, int numWrites, int numReads, Statement s)
      throws RpcThrottlingException {
    OperationQuota quota = getQuota(userName);
    quota.checkQuota(numWrites, numReads, s);
    return quota;
  }
Check the quota for the current (rpc-context) user. Returns the {@link OperationQuota} used to
get the available quota and to report the data/usage of the operation.

@param userName userName of the current user
@param numWrites number of writes to perform
@param numReads number of short-reads to perform
@return the {@link OperationQuota}
@throws RpcThrottlingException if the operation cannot be executed due to quota exceeded.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/rescon/quotas/DataNodeThrottleQuotaManager.java