[#MDEV-17385] MICROSECOND() returns confusing results with an out-of-range TIME-alike argument

Notice a similar bug ~~MDEV-17351~~ (which is about hybrid functions).

MICROSECOND(arg) can return 999999 in some contexts where TIME(arg) returns a result without fractional digits.
Internally, the argument gets converted to the maximum possible TIME value of '838:59:59.999999'.

Confusing examples when a number gets converted to '838:59:59.999999'

SELECT

  TIME(8395959) AS c1,

  MICROSECOND(8395959) AS c2;

+-----------+--------+

| c1        | c2     |

+-----------+--------+

| 838:59:59 | 999999 |

+-----------+--------+

SELECT

  TIME(8395959.0) AS c1,

  MICROSECOND(8395959.0) AS c2;

+-------------+--------+

| c1          | c2     |

+-------------+--------+

| 838:59:59.9 | 999999 |

+-------------+--------+

SELECT

  TIME(CAST(8395959 AS SIGNED)) AS c1,

  MICROSECOND(CAST(8395959 AS SIGNED)) AS c2;

+-----------+--------+

| c1        | c2     |

+-----------+--------+

| 838:59:59 | 999999 |

+-----------+--------+

SELECT

  TIME(CAST(8395959 AS DECIMAL(30,1))) AS c1,

  MICROSECOND(CAST(8395959 AS DECIMAL(10,1))) AS c2;

+-------------+--------+

| c1          | c2     |

+-------------+--------+

| 838:59:59.9 | 999999 |

+-------------+--------+

SELECT

  TIME(COLUMN_GET(COLUMN_CREATE(0, 8395959), 0 AS SIGNED)) AS c1,

  MICROSECOND(COLUMN_GET(COLUMN_CREATE(0, 8395959), 0 AS SIGNED)) AS c2;

+-----------+--------+

| c1        | c2     |

+-----------+--------+

| 838:59:59 | 999999 |

+-----------+--------+

More confusing examples when a string gets converted to '838:59:59.999999'

Intuitively, an explicit conversion from string to time using the TIME() function, and an implicit conversion of a function argument (from a non-TIME actual parameter to TIME formal parameter) should return the same result. But they do not, because of different ways of precision detection for string arguments (mentioned in the previous paragraph):

SELECT

  TIME('839:59:59') AS c0,

  MICROSECOND(TIME('839:59:59')) AS explicit,

  MICROSECOND('839:59:59') AS implicit;

+-----------+----------+----------+

| c0        | explicit | implicit |

+-----------+----------+----------+

| 838:59:59 |        0 |   999999 |

+-----------+----------+----------+

[MDEV-17385] MICROSECOND() returns confusing results with an out-of-range TIME-alike argument Created: 2018-10-07 Updated: 2018-11-26
Status:	Open
Project:	MariaDB Server
Component/s:	Data types, Temporal Types
Affects Version/s:	5.5, 10.0, 10.1, 10.2, 10.3, 10.4
Fix Version/s:	10.4

[MDEV-17385] MICROSECOND() returns confusing results with an out-of-range TIME-alike argument Created: 2018-10-07 Updated: 2018-11-26

Confusing examples when a number gets converted to '838:59:59.999999'

More confusing examples when a string gets converted to '838:59:59.999999'