HandleBinaryLiteral should ignore TypeNull

[YangKeao]

Enhancement

from_binary(<nil>) actually does nothing, but TiDB regards the NULL as binary string, so it may avoid some expressions to be pushed down to TiFlash. We can manually ignore this case.

(Though I don't know why this constant is not folded.)

[kennedy8312]

/type regression

[kennedy8312]

v5.4.0 seems to be the first release using "cast(from_binary()".

[kennedy8312]

v5.3.0 seems to be fine.

[kennedy8312]

Regression Analysis
PR caused this regression: #30706

[kennedy8312]

+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v5.4.0-alpha-458-geb6c89d6d4-dirty
Edition: Community
Git Commit Hash: eb6c89d
Git Branch: HEAD
UTC Build Time: 2024-02-01 10:04:22
GoVersion: go1.21.4
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)

mysql> explain select null as a union all select 'a' as a order by a;
+--------------------------+---------+------+---------------+-----------------+
| id | estRows | task | access object | operator info |
+--------------------------+---------+------+---------------+-----------------+
| Sort_9 | 2.00 | root | | Column#3 |
| └─Union_11 | 2.00 | root | | |
| ├─Projection_13 | 1.00 | root | | ->Column#3 |
| │ └─TableDual_14 | 1.00 | root | | rows:1 |
| └─Projection_15 | 1.00 | root | | a->Column#3 |
| └─TableDual_16 | 1.00 | root | | rows:1 |
+--------------------------+---------+------+---------------+-----------------+
6 rows in set (0.00 sec)

mysql> select null as a union all select 'a' as a order by a;
+---+
| a |
+---+
| NULL |
| a |
+---+
2 rows in set (0.01 sec)

[kennedy8312]

mysql> explain select null as a union all select 'a' as a order by a;
+--------------------------+---------+------+---------------+---------------------------------------------------+
| id | estRows | task | access object | operator info |
+--------------------------+---------+------+---------------+---------------------------------------------------+
| Sort_9 | 2.00 | root | | Column#3 |
| └─Union_11 | 2.00 | root | | |
| ├─Projection_13 | 1.00 | root | | cast(from_binary(), var_string(1))->Column#3 |
| │ └─TableDual_14 | 1.00 | root | | rows:1 |
| └─Projection_15 | 1.00 | root | | a->Column#3 |
| └─TableDual_16 | 1.00 | root | | rows:1 |
+--------------------------+---------+------+---------------+---------------------------------------------------+
6 rows in set (0.00 sec)

mysql> select null as a union all select 'a' as a order by a;
+---+
| a |
+---+
| NULL |
| a |
+---+
2 rows in set (0.01 sec)

mysql> select tidb_version();
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version() |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v5.4.0-alpha-459-g87ab28ebb2-dirty
Edition: Community
Git Commit Hash: 87ab28e
Git Branch: HEAD
UTC Build Time: 2024-02-01 10:09:06
GoVersion: go1.21.4
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |

[kennedy8312]

/type performance