Re: BUG #17876: Function width_bucket() for float8 input returns value out of range

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От Mats Kindahl
Тема Re: BUG #17876: Function width_bucket() for float8 input returns value out of range
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Msg-id CA+14427KvPsskajKSriGACyrudcOyh5ohmt=0WPuNjoMTSQM6A@mail.gmail.com
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Ответы Re: BUG #17876: Function width_bucket() for float8 input returns value out of range  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-bugs
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Hi all,

Attached is a proposed fix for the issue. It has extended the tests to cover these cases and also some additional tests for values close to DBL_MIN. I compared the old and new version using the attached program with the following result:

DBL_MAX: 1.797693e+308, DBL_MIN: 2.225074e-308
 1.04000e+01, low: -1.79769e+308, high:  1.79769e+308, count:  10 --> orig: -2147483648, new:  6
-8.98847e+307, low: -1.79769e+308, high:  1.79769e+308, count:  10 --> orig: -2147483648, new:  3
 8.98847e+307, low: -1.79769e+308, high:  1.79769e+308, count:  10 --> orig: -2147483648, new:  8
 1.04000e+01, low: -1.79769e+308, high:  1.79769e+308, count:  12 --> orig: -2147483648, new:  7
-8.98847e+307, low: -1.79769e+308, high:  1.79769e+308, count:  12 --> orig: -2147483648, new:  4
 8.98847e+307, low: -1.79769e+308, high:  1.79769e+308, count:  12 --> orig: -2147483648, new:  10
 1.04000e+01, low: -1.79769e+308, high:  1.79769e+308, count:  1 --> orig:  1, new:  1
-8.98847e+307, low: -1.79769e+308, high:  1.79769e+308, count:  1 --> orig:  1, new:  1
 8.98847e+307, low: -1.79769e+308, high:  1.79769e+308, count:  1 --> orig: -2147483648, new:  1
 1.04000e+01, low: -1.79769e+308, high:  1.79769e+308, count:  2 --> orig: -2147483648, new:  2
-8.98847e+307, low: -1.79769e+308, high:  1.79769e+308, count:  2 --> orig:  1, new:  1
 8.98847e+307, low: -1.79769e+308, high:  1.79769e+308, count:  2 --> orig: -2147483648, new:  2
 5.35000e+00, low:  2.40000e-02, high:  1.00600e+01, count:  5 --> orig:  3, new:  3
 2.22507e-308, low: -4.45015e-308, high:  4.45015e-308, count:  4 --> orig:  4, new:  4
-2.22507e-308, low: -4.45015e-308, high:  4.45015e-308, count:  4 --> orig:  2, new:  2
 2.22507e-308, low: -6.67522e-308, high:  6.67522e-308, count:  4 --> orig:  3, new:  3
-2.22507e-308, low: -6.67522e-308, high:  6.67522e-308, count:  4 --> orig:  2, new:  2
 2.22507e-308, low: -6.67522e-308, high:  6.67522e-308, count:  6 --> orig:  5, new:  5
-2.22507e-308, low: -6.67522e-308, high:  6.67522e-308, count:  6 --> orig:  3, new:  3

As you can see, the old and new computations seem to produce the same values also for values close to DBL_MIN.

On Wed, Mar 29, 2023 at 10:12 AM PG Bug reporting form <noreply@postgresql.org> wrote:
The following bug has been logged on the website:

Bug reference:      17876
Logged by:          Mats Kindahl
Email address:      mats@timescale.com
PostgreSQL version: 15.2
Operating system:   All
Description:       

On 64-bit platforms, the existing width_bucket() computation can
result in a NaN (0x8000000) if the difference between the `operand`,
`low`, or `high` parameters exceeds DBL_MAX. This is then cast to the
value -2147483648.

    mats=# WITH sample(operand, low, high, cnt) AS (
      VALUES
        (10.5::float8, -1.797e+308::float8, 1.797e+308::float8, 1::int4),
        (10.5::float8, -1.797e+308::float8, 1.797e+308::float8, 2),
        (10.5::float8, -1.797e+308::float8, 1.797e+308::float8, 3),

        (1.797e+308::float8 / 2, -1.797e+308::float8, 1.797e+308::float8, 10),
        (-1.797e+308::float8 / 2, -1.797e+308::float8, 1.797e+308::float8, 10),

        (1.797e+308::float8 / 2, -1.797e+308::float8, 1.797e+308::float8, 16),
        (-1.797e+308::float8 / 2, -1.797e+308::float8, 1.797e+308::float8, 16),

        (1.797e+308::float8, -1.797e+308::float8 / 2, 1.797e+308::float8 / 2,
10),
        (-1.797e+308::float8, -1.797e+308::float8 / 2, 1.797e+308::float8 / 2,
10)
    ) SELECT width_bucket(operand, low, high, cnt) FROM sample;
     width_bucket
    --------------
                1
      -2147483648
      -2147483648
      -2147483648
      -2147483648
      -2147483648
      -2147483648
               11
                0
    (9 rows)

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