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  1. MariaDB Server
  2. MDEV-5699

CAST(TIME'10:10:10' AS DATE) - regression

        Details

        • Type: Bug
        • Status: Open
        • Priority: Minor
        • Resolution: Unresolved
        • Affects Version/s: 10.0.8
        • Fix Version/s: 10.0
        • Component/s: None
        • Labels:
          None

          Description

          CAST(TIME'10:10:10' AS DATE) returns '2010-10-10' in MariaDB-5.5 and
          in MySQL.

          MariaDB-10.0 returns '0000-00-00'.

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                serg Sergei Golubchik added a comment -

                Is that bad? I think the new result is ok. The date part of TIME'10:10:10' is DATE'0000-00-00'. You can see that explicitly when casting to datetime, it'll be DATETIME'0000-00-00 10:10:10'.

                There's no logical explanation why the date part of TIME'10:10:10' shoud be '2010-10-10'. And I don't consider "because we internally cast time to a string and then to date" a particularly convincing explanation.

                Compare, for example, with double→integer cast:

                MariaDB [test]> select concat(1e15), cast(1e15 as unsigned);
+--------------+------------------------+
| concat(1e15) | cast(1e15 as unsigned) |
+--------------+------------------------+
| 1e15         |       1000000000000000 |
+--------------+------------------------+

                when casted to a string, it's "1e15". If you cast this string to an integer, you get "1". But double→integer cast is not using strings, that's you get the correct result — the integer part of the floating-point number.

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                serg Sergei Golubchik added a comment - Is that bad? I think the new result is ok. The date part of TIME'10:10:10' is DATE'0000-00-00'. You can see that explicitly when casting to datetime, it'll be DATETIME'0000-00-00 10:10:10'. There's no logical explanation why the date part of TIME'10:10:10' shoud be '2010-10-10'. And I don't consider "because we internally cast time to a string and then to date" a particularly convincing explanation. Compare, for example, with double→integer cast: MariaDB [test]> select concat(1e15), cast(1e15 as unsigned); +--------------+------------------------+ | concat(1e15) | cast(1e15 as unsigned) | +--------------+------------------------+ | 1e15 | 1000000000000000 | +--------------+------------------------+ when casted to a string, it's "1e15". If you cast this string to an integer, you get "1". But double→integer cast is not using strings, that's you get the correct result — the integer part of the floating-point number.

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                  • Assignee:
                    bar Alexander Barkov
                    Reporter:
                    bar Alexander Barkov
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                    Dates

                    • Created:
                      Updated: