On Thu, Feb 25, 2021 at 7:11 AM Michael Davis <[email protected]>
wrote:
> I insert dates into a database, the column type is DateTime, and dates
> being inserted are strings with just date values (no time values and no
> timezone). I confirm in the database that the date values are correct and
> have no timezones. When I select the date fields all dates have 00:00:00
> for the time as expected but some dates come back in CST and other dates
> come back in MST. This happens in mssql, tinytds, access, and sqlite.
When debugging this in sqlite, I see Time.localtime() being called with the
> correct date and time values and no timezone, however each Time value comes
> back randomly with CST or MST for the timezone. I was expecting dates all
> to comeback as MST which is my local timezone.
>
> Here are my questions:
>
> 1. is this a bug in Time.localtime?
>
> No.
>
> 1. why does it sometimes pick CST and other times pick MST? The
> timezones seem to be consistent across databases and across runs so this
> does not appear to be random.
>
> This isn't a different time zone, this is the same time zone with
daylight savings time handling. This is normal Time behavior when parsing
times when the local timezone uses daylight savings time.
>
> 1. can I control what happens when DateTime or Time values are read in
> as a string and converted to a Time value?
>
> Whether you can depends on the adapter. tinytds for example does its own
conversion, outside of Sequel.
>
> 1. can I set the timezone to something specific?
>
> You can use the named_timezones extension to select a specific timezone.
Maybe you can find an appropriate timezone that doesn't use daylight
savings time, if you want all timezone offsets to be the same.
>
> 1. can I disable the DateTime conversion all together?
>
> You could always cast the column to String, that should work on every
adapter. Without that, behavior is dependent on the adapter.
> Setting Sequel.default_timezone = :local does not change the outcome.
>
This is expected as local is the default if Sequel.datetime_class is Time
(which is also the default).
I prefer to just circumvent the DateTime conversions and let the values
> come back as Strings. Is that possible? I could not see an easy way to do
> then debugging through the issue.
>
As mentioned above, you can cast the value to String. If you don't want to
do that, here's an example for the sqlite adapter:
DB.create_table(:t) do
column :t, :DateTime
end
DB[:t].insert(Time.now)
DB[:t].get(:t)
# => 2021-02-25 08:10:49.241774 -0800
DB.conversion_procs.delete('datetime')
DB[:t].get(:t)
# => "2021-02-25 08:10:49.241774"
Note that the values in the database are actually dates and not
datetimes/timestamps. You should probably change the column type from
DateTime to date to reflect that. Then you would get Date objects back.
If you don't want to change the column type, one workaround for the sqlite
adpater is to make the datetime conversion the same as the date conversion.
DB.conversion_procs['datetime'] = DB.conversion_procs['date']
DB[:t].get(:t)
# => #<Date: 2021-02-25 ((2459271j,0s,0n),+0s,2299161j)>
Thanks,
Jeremy
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