maria-developers team mailing list archive

[Marko Mäkelä <marko.makela@xxxxxxxxxxx>]

Hi Aleksey,

I think that we should remove trx_t::start_time, and always use
trx_t::start_time_micro.

I shortly discussed this with Vladislav Vaintroub, and he mentioned that
the microsecond timestamp in THD::start_utime is updated at the start of
each statement.
I also looked at his MDEV-12345 performance fix
<https://github.com/MariaDB/server/commit/e5b67a46bcb75a751f5906f19694971bc803d67c>.
It looks like trx_start_low() is already doing the right thing, except that
the trx_t::start_time should be removed.

I'd welcome a contributed patch that removes trx_t:.start_time. Or if that
really is too tricky, convert start_time_micro to start_time.

Marko

On Thu, Nov 16, 2017 at 11:29 AM, Aleksey Midenkov <midenok@xxxxxxxxx>
wrote:

> Hello!
>
> Different semantics of these 2 members doesn't look good:
>
> time_t start_time; /*!< time the state last time became
> TRX_STATE_ACTIVE */
> ib_uint64_t start_time_micro; /*!< start time of transaction in
> microseconds */
>
> Either `start_time_micro` should be drawn to the base of `start_time`
> or it should be explicitly commented that it has nothing to do with
> `start_time`. I.e. there is nothing wrong on algorithmic level, but
> such data members may (and certainly would) lead developers to misuse
> of `start_time_micro`.
>
> --
> All the best,
>
> Aleksey Midenkov
> @midenok
>
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-- 
Marko Mäkelä, Lead Developer InnoDB
MariaDB Corporation

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