sqlobject-discuss

[SQLObject] Binary data

[Javier R. <jav...@Ho...>]

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Hi,
	How can binary data be stored with SQLObject?
	I'm trying to pickle something and storing it but caracters are scaped.
How can I avoid this?

Later,
	Javier
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Re: [SQLObject] Binary data

[Ian B. <ia...@co...>]

On Saturday, August 9, 2003, at 07:25 PM, Javier Ruere wrote:
> 	How can binary data be stored with SQLObject?
> 	I'm trying to pickle something and storing it but caracters are 
> scaped.
> How can I avoid this?
>
This response is a little late, but I don't see another response.

There's an option to Pickle to use a string representation, but that's 
only really a string if all the components can be represented as 
strings (i.e., you don't have any binary instance variables in your 
objects).

I haven't really used much binary data, so I'm not sure how to 
represent that to the database.  Obviously the data must be escaped 
somehow.  If you figure it out for your database, and say make a 
dbEscape() function that creates the SQL version of the value (complete 
with '' if necessary) you could so something like:

class Binary:
     def __init__(self, value):
         self.value = value
     def sqlRepr(self):
         return dbEscape(self.value)

You could also use something like base64, like:

     def _set_binaryColumn(self, value):
          self._SO_set_binaryColumn(value.encode('base64'))
     def _get_binaryColumn(self):
          return self._SO_get_binaryColumn().decode('base64')

   Ian

Re: [SQLObject] Binary data

[Javier R. <jav...@Ho...>]

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Ian,
    Thanks for answering.

Ian Bicking wrote:

> On Saturday, August 9, 2003, at 07:25 PM, Javier Ruere wrote:
>
>>     How can binary data be stored with SQLObject?
>>     I'm trying to pickle something and storing it but caracters are
>> scaped.
>> How can I avoid this?
>>
> This response is a little late, but I don't see another response.
>
> There's an option to Pickle to use a string representation, but that's
> only really a string if all the components can be represented as strings
> (i.e., you don't have any binary instance variables in your objects).

  Yes, I already tried this but doesn't seem to work. For example:

	>>> pickle.dumps('Hello')
	"S'Hello'\np0\n."

  The pickle of 'Hello' has a '\n' in it which when passed through
SQLObject returns as '\\n' which cannot be unpickled. I worked around
this be searching for the function which does this modification, copying
the list of tuples and making the inverse operation.
  Why is this done? I tried storing strings with '\n' in SQLite and it
seems to work alright. Is there a problem with the other DBs? I will be
using this system with SQLite and Postgress eventually so I would be
very interested in knowing this.

> I haven't really used much binary data, so I'm not sure how to represent
> that to the database.  Obviously the data must be escaped somehow.  If
> you figure it out for your database, and say make a dbEscape() function
> that creates the SQL version of the value (complete with '' if
> necessary) you could so something like:
>
> class Binary:
>     def __init__(self, value):
>         self.value = value
>     def sqlRepr(self):
>         return dbEscape(self.value)
>
> You could also use something like base64, like:
>
>     def _set_binaryColumn(self, value):
>          self._SO_set_binaryColumn(value.encode('base64'))
>     def _get_binaryColumn(self):
>          return self._SO_get_binaryColumn().decode('base64')

  I have check this possibility as well but they all count on using '\n'
so there would be little benefit.

Later,
	Javier

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