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Two decimal literals:
0.1111111111222222222233333333334444444444
and
0.111111111122222222223333333333
are considered as non-equal by "=",
but considered as equal for UNION DISTINCT:
MariaDB [test]> SELECT 0.1111111111222222222233333333334444444444 = 0.111111111122222222223333333333 AS cmp;
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+-----+
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| cmp |
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+-----+
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| 0 |
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+-----+
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1 row in set (0.00 sec)
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MariaDB [test]> SELECT 0.1111111111222222222233333333334444444444 AS a UNION SELECT 0.111111111122222222223333333333;
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+----------------------------------+
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| a |
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+----------------------------------+
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| 0.111111111122222222223333333333 |
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+----------------------------------+
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1 row in set (0.01 sec)
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Comparison in "=" and comparison in UNION DISTINCT should use the same rules.
The problem most likely happens because we don't support fields with decimal
scale > 30. UNION uses a temporary table and creates a field,
while '=' does not need a field and compares the two numbers directly.
Literals should probably be fixed not to support more than 30 fractional as well.
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