scan a full table consume more memory than I expected

[tiancaiamao]

Enhancement

mysql> select count(*) from ens_rb.fm_acct_client_relation;
+----------+
| count(*) |
+----------+
| 50000000 |
+----------+
1 row in set (2.55 sec)

CREATE TABLE `fm_acct_client_relation` (
  `CLIENT_NO` varchar(20) DEFAULT NULL,
  `BASE_ACCT_NO` varchar(150) DEFAULT NULL,
  `INTERNAL_KEY` decimal(15,0) DEFAULT NULL,
  `CARD_NO` varchar(50) DEFAULT NULL,
  `BRANCH` varchar(20) DEFAULT NULL,
  `COMPANY` varchar(20) DEFAULT NULL,
  `SHARD_ID` varchar(10) DEFAULT NULL,
  `TRAN_TIMESTAMP` datetime DEFAULT NULL,
  `PROD_TYPE` varchar(50) DEFAULT NULL,
  `CCY` varchar(3) DEFAULT NULL,
  `ACCT_SEQ_NO` varchar(8) DEFAULT NULL,
  `CLIENT_TYPE` varchar(3) DEFAULT NULL,
  `ACCT_NATURE` varchar(4) DEFAULT NULL,
  `ACCT_CLASS` varchar(2) DEFAULT NULL,
  `SOURCE_TYPE` varchar(10) DEFAULT NULL,
  `ACCT_STATUS` varchar(3) DEFAULT NULL,
  `ACCT_REAL_FLAG` varchar(1) DEFAULT NULL,
  `ACCT_NAME` varchar(200) DEFAULT NULL,
  `REASON_CODE` varchar(200) DEFAULT NULL,
  `IS_CARD` varchar(1) DEFAULT NULL,
  `LEAD_ACCT_FLAG` varchar(1) DEFAULT NULL,
  `PARENT_INTERNAL_KEY` decimal(15,0) DEFAULT NULL,
  `DEFAULT_SETTLE_ACCT` varchar(1) DEFAULT NULL,
  `DOCUMENT_TYPE` varchar(3) DEFAULT NULL,
  `IS_INDIVIDUAL` varchar(1) DEFAULT NULL,
  `DOCUMENT_ID` varchar(40) DEFAULT NULL,
  `ACTUAL_ACCT_NO` varchar(150) DEFAULT NULL,
  `APP_FLAG` varchar(1) DEFAULT NULL,
  `IS_CORP_SETTLE_CARD` varchar(1) DEFAULT NULL,
  `loginid` bigint(20) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`loginid`) /*T![clustered_index] CLUSTERED */,
  UNIQUE KEY `UN_IDX_RELATION` (`CARD_NO`,`ACCT_SEQ_NO`,`PROD_TYPE`,`BASE_ACCT_NO`,`CCY`),
  KEY `FACR_IND1` (`CLIENT_NO`),
  KEY `FACR_IND2` (`BASE_ACCT_NO`),
  KEY `FACR_IND3` (`CARD_NO`),
  KEY `FACR_IND4` (`INTERNAL_KEY`),
  KEY `FACR_IND5` (`ACTUAL_ACCT_NO`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin AUTO_INCREMENT=50100001

time mysql -h 127.0.0.1 -u root -P 4000 -B ens_rb -e 'set @@tidb_enable_paging = 1; select * from ens_rb.fm_acct_client_relation' > /dev/null

real	2m32.847s
user	1m37.531s
sys	0m7.384s

Even with paging, it still takes too much memory than I expected.
There must be something wrong.