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Something appears to be wrong with processing of nested NULLIF in 10.1. The example below is exaggerated to the point of being senseless intentionally, to show the clear difference in query execution time.
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10.1
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MariaDB [test]> CREATE TABLE t1 (i INT);
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Query OK, 0 rows affected (0.09 sec)
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MariaDB [test]> INSERT INTO t1 VALUES (1),(2);
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Query OK, 2 rows affected (0.00 sec)
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Records: 2 Duplicates: 0 Warnings: 0
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MariaDB [test]>
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MariaDB [test]> SELECT * FROM t1 WHERE
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-> NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(
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-> NULLIF(1,1),
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-> NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(1,1),1),1),1),1),1),1),1),1),1)
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-> ),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1);
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Empty set (1 min 10.76 sec)
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MariaDB [test]> select @@version;
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+-----------------+
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| @@version |
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+-----------------+
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| 10.1.12-MariaDB |
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+-----------------+
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1 row in set (0.00 sec)
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MySQL 5.6
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MySQL [test]> CREATE TABLE t1 (i INT);
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Query OK, 0 rows affected (0.28 sec)
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MySQL [test]> INSERT INTO t1 VALUES (1),(2);
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Query OK, 2 rows affected (0.00 sec)
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Records: 2 Duplicates: 0 Warnings: 0
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MySQL [test]>
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MySQL [test]> SELECT * FROM t1 WHERE
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-> NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(
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-> NULLIF(1,1),
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-> NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(1,1),1),1),1),1),1),1),1),1),1)
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-> ),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1);
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Empty set (0.02 sec)
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MySQL [test]> select @@version;
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+-----------+
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| @@version |
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+-----------+
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| 5.6.28 |
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+-----------+
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1 row in set (0.00 sec)
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10.0
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MySQL [test]> CREATE TABLE t1 (i INT);
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Query OK, 0 rows affected (0.28 sec)
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MariaDB [test]> INSERT INTO t1 VALUES (1),(2);
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Query OK, 2 rows affected (0.39 sec)
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Records: 2 Duplicates: 0 Warnings: 0
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MariaDB [test]>
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MariaDB [test]> SELECT * FROM t1 WHERE
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-> NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(
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-> NULLIF(1,1),
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-> NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(1,1),1),1),1),1),1),1),1),1),1)
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-> ),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1);
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Empty set (0.02 sec)
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MariaDB [test]> select @@version;
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+-----------------+
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| @@version |
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+-----------------+
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| 10.0.24-MariaDB |
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+-----------------+
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1 row in set (0.00 sec)
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Test case
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CREATE TABLE t1 (i INT);
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INSERT INTO t1 VALUES (1),(2);
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SELECT * FROM t1 WHERE
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NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(
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NULLIF(1,1),
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NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(1,1),1),1),1),1),1),1),1),1),1)
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),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1),1);
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