sqlobject-discuss

[SQLObject] DateTimeCol with microsecond resolution.

[Ben T. <bt...@gm...>]

I really need to store date/time values with millisecond resolution.
What would be the easiest way to achieve this? I found the following
patch:

http://permalink.gmane.org/gmane.comp.python.sqlobject/5106

But I am loath to apply a patch to SQLObject since my code must be portable.

Must I create my own column type? Is there any way to override the
storage method of DateTimeCol? I tried passing a datetimeFormat to the
DateTimeCol.__init__() but this did not have the desired effect. I am
assuming the TIMESTAMP data type of sqlite does not support this level
of resolution? If so, I suppose I must store the date as a string in
ISO 8601 format?

Thanks.

Re: [SQLObject] DateTimeCol with microsecond resolution.

[Oleg B. <ph...@ph...>]

On Tue, Feb 01, 2011 at 12:26:34PM -0500, Ben Timby wrote:
> I really need to store date/time values with millisecond resolution.
> What would be the easiest way to achieve this? I found the following
> patch:
> 
> http://permalink.gmane.org/gmane.comp.python.sqlobject/5106
> 
> But I am loath to apply a patch to SQLObject since my code must be portable.

   You couldn't apply it anyway - it's too old.

> Must I create my own column type? Is there any way to override the
> storage method of DateTimeCol? I tried passing a datetimeFormat to the
> DateTimeCol.__init__() but this did not have the desired effect. I am
> assuming the TIMESTAMP data type of sqlite does not support this level
> of resolution? If so, I suppose I must store the date as a string in
> ISO 8601 format?

   You don't understand all subtle details of SQLObject (which is ok).
The architecture works this way: to convert data to an SQL string column
validator's .from_python() method is called, and whatever it returns
(including a simple string) is passed to converters (see converters.py).
   If you want to override datetime converter for all datetime columns -
just register your own converter:

def DateTimeConverter(value, db):
    return "'%s'" % value.isoformat

registerConverter(datetime.datetime, DateTimeConverter)

Oleg.
-- 
     Oleg Broytman            http://phdru.name/            ph...@ph...
           Programmers don't die, they just GOSUB without RETURN.

Re: [SQLObject] DateTimeCol with microsecond resolution.

[Oleg B. <ph...@ph...>]

On Tue, Feb 01, 2011 at 09:13:35PM +0300, Oleg Broytman wrote:
> def DateTimeConverter(value, db):
>     return "'%s'" % value.isoformat

   Oops, sorry, a bug:

    return "'%s'" % value.isoformat()

> 
> registerConverter(datetime.datetime, DateTimeConverter)

Oleg.
-- 
     Oleg Broytman            http://phdru.name/            ph...@ph...
           Programmers don't die, they just GOSUB without RETURN.

Re: [SQLObject] DateTimeCol with microsecond resolution.

[Ben T. <bt...@gm...>]

On Tue, Feb 1, 2011 at 1:24 PM, Oleg Broytman <ph...@ph...> wrote:
> On Tue, Feb 01, 2011 at 09:13:35PM +0300, Oleg Broytman wrote:
>> def DateTimeConverter(value, db):
>>     return "'%s'" % value.isoformat
>
>   Oops, sorry, a bug:
>
>    return "'%s'" % value.isoformat()
>
>>
>> registerConverter(datetime.datetime, DateTimeConverter)

Thank you as always Oleg for your prompt reply.

I will give this a try, meanwhile I have created my own column type:

--
class ISO8601Validator(validators.Validator):
   def from_python(self, value, state):
       if value is not None:
           value = value.strftime('%Y-%m-%d %H:%M:%S.%f')
       return value

   def to_python(self, value, state):
       if value is not None:
           value = datetime.datetime.strptime(value, '%Y-%m-%d %H:%M:%S.%f')
       return value

class SOISO8601Col(SOStringCol):
   def createValidators(self):
       return [ISO8601Validator()] + \
           super(SOISO8601Col, self).createValidators()

class ISO8601Col(StringCol):
   baseClass = SOISO8601Col
--

This seems to work for me. Will registering a converter work both
ways? i.e. the value is transformed to string for storage and back
again for retrieval?

Re: [SQLObject] DateTimeCol with microsecond resolution.

[Oleg B. <ph...@ph...>]

On Tue, Feb 01, 2011 at 01:54:03PM -0500, Ben Timby wrote:
> Will registering a converter work both
> ways? i.e. the value is transformed to string for storage and back
> again for retrieval?

   No, converters work one way - from python data type to SQL string.

Oleg.
-- 
     Oleg Broytman            http://phdru.name/            ph...@ph...
           Programmers don't die, they just GOSUB without RETURN.

Re: [SQLObject] DateTimeCol with microsecond resolution.

[Petr J. <pet...@tp...>]

>
> I will give this a try, meanwhile I have created my own column type:
>
> --
> class ISO8601Validator(validators.Validator):
>   def from_python(self, value, state):
>       if value is not None:
>           value = value.strftime('%Y-%m-%d %H:%M:%S.%f')
>       return value
>
>   def to_python(self, value, state):
>       if value is not None:
>           value = datetime.datetime.strptime(value, '%Y-%m-%d %H:%M:%S.%f')
>       return value
>
> class SOISO8601Col(SOStringCol):
>   def createValidators(self):
>       return [ISO8601Validator()] + \
>           super(SOISO8601Col, self).createValidators()
>
> class ISO8601Col(StringCol):
>   baseClass = SOISO8601Col
> --
>
> If you want to go your own way, what about magic attributes?

http://www.sqlobject.org/SQLObject.html#adding-magic-attributes-properties

I think it is possible to store the time value as decimal and when in the
time of reading you can convert it into the desired format.

Regards

Petr