executor: Fix a bug in 'INSERT ... ON DUPLICATE KEY UPDATE'

[bb7133]

What problem does this PR solve?

Fix a bug in 'INSERT ... ON DUPLICATE KEY UPDATE' when unique key are updated, for example:

mysql> select * from t1;
+------+------+------+
| id   | a    | b    |
+------+------+------+
|    1 |    1 |    1 |
|    2 |    1 |    2 |
|    3 |    3 |    1 |
+------+------+------+
3 rows in set (0.00 sec)

mysql> create table t2(a int key, b int, unique(b));
Query OK, 0 rows affected (0.08 sec)

mysql> insert into t2 select a, b from t1 order by id on duplicate key update a=t1.a, b=t1.b;
Query OK, 6 rows affected (0.01 sec)

mysql> select * from t2;
+---+------+
| a | b    |
+---+------+
| 3 |    1 |
+---+------+
1 row in set (0.00 sec)

, which is incorrect. We should expect the following result instead:

mysql> select * from t2;
+---+------+
| a | b    |
+---+------+
| 1 |    2 |
| 3 |    1 |
+---+------+
2 rows in set (0.00 sec)

After this PR, it will be fixed.

What is changed and how it works?

In InsertExec's updateDupKeyValues function, dupKVs(a map that holds existing primary keys and unique keys for duplication detection) is updated by removing keys from the inserting row first, then adding keys from the updated row. But we should remove keys from the old row instead, because old row is the one that to be replaced.

Check List

Tests

• Integration test

Code changes

• Has exported function/method change

Side effects

• No side effect

Related changes

• Nothing else

[bb7133]

@jackysp @zz-jason PTAL, thanks!

[zz-jason]

@XuHuaiyu @winoros PTAL

[zz-jason]

/run-all-tests

[zz-jason]

LGTM

[shenli]

@jackysp PTAL

[jackysp]

We could use a function to handle this part and

tidb/executor/replace.go

Line 73 in 9070bb6

// Cleanup keys map, because the record was removed.

together.

[bb7133]

Thanks for the review @jackysp, I plan to define a function for this and put it in the base struct InsertValues, what do u think?

[jackysp]

I think to put it into batchChecker is better. Thanks for your contribution, @bb7133 !

[bb7133]

Comments addressed, PTAL @jackysp , thanks!

[jackysp]

LGTM
Thanks @bb7133 !

[jackysp]

/run-all-tests

[bb7133]

Thank you @jackysp