user variables in LOAD DATA don't work as expected

[kolbe]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.

data.csv:

1,c

table:

CREATE TABLE `t` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `c` char(1) DEFAULT NULL,
  PRIMARY KEY (`id`)
);

statement:

load data local infile 'data.csv' into table t fields terminated by ',' (id, @c) set c=upper(@c);

2. What did you expect to see?

This should load the data from the file into the table, setting the value of column c to the uppercased value of the 2nd column in the CSV file, as occurs in MariaDB:

MariaDB [test]> load data local infile 'data.csv' into table t fields terminated by ',' (id, @c) set c=upper(@c);
Query OK, 1 row affected (0.002 sec)
Records: 1  Deleted: 0  Skipped: 0  Warnings: 0

MariaDB [test]> select * from t;
+----+------+
| id | c    |
+----+------+
|  1 | C    |
+----+------+
1 row in set (0.001 sec)

3. What did you see instead?

TiDB [test]> load data local infile 'data.csv' into table t fields terminated by ',' (id, @c) set c=upper(@c);
Query OK, 1 row affected (0.01 sec)
Records: 1  Deleted: 0  Skipped: 0  Warnings: 0

TiDB [test]> select * from t;
+----+------+
| id | c    |
+----+------+
|  1 | NULL |
+----+------+
1 row in set (0.00 sec)

4. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?

tidb_version(): Release Version: v3.0.3
Git Commit Hash: 836982c617fbaa42d74616eb9ba9ed4cae46c46b
Git Branch: HEAD
UTC Build Time: 2019-08-29 04:59:41
GoVersion: go version go1.12 linux/amd64
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false

[lysu]

@kolbe #7707 nearly fixes this, but it be paused due to the priority and go to do other things at that time 😞 I can restart it if we need it 😄

[ghost]

Verified against master:

mysql> load data local infile '/tmp/data.csv' into table t fields terminated by ',' (id, @c) set c=upper(@c);
Query OK, 1 row affected (0.02 sec)
Records: 1  Deleted: 0  Skipped: 0  Warnings: 0

mysql> select * from t;
+----+------+
| id | c    |
+----+------+
|  1 | NULL |
+----+------+
1 row in set (0.00 sec)

mysql> select tidb_version()\G
*************************** 1. row ***************************
tidb_version(): Release Version: v4.0.0-beta.2-769-g2024e4463
Edition: Community
Git Commit Hash: 2024e44636f2fb9798982a1cc0ec22176e07f5c1
Git Branch: master
UTC Build Time: 2020-07-14 09:26:07
GoVersion: go1.13
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false
1 row in set (0.00 sec)

[ghost]

Fixed in #18753 (not closed due to issue in close syntax.)