Re: [SQLObject] Error writing binary data to a blob

[Aaron R. <aar...@mo...>]

Hi Oleg,

That's terrific - thanks very much for your response.

First off, the point you raised about setting many values at once; yes, I
was aware of this, but a lot of the things we seem to want to do are more
like we have a dict with strings for keys and associated values, and we want
to write them into the db in one go, where the strings are the column names
- is there's some way to do a myObject.set(), and pass in a dictionary? (or
some python semantic that yields the same result?.. I'm not sure).

Okay, I completely understand the distinction between SQLObject and
SQLBuilder now, and it makes perfect sense - thanks! Just by the way, is
there any way to do transactions with SQLObject's?

Thanks again,
-Aaron.


On Fri, Jul 24, 2009 at 7:59 PM, Oleg Broytmann <ph...@ph...> wrote:

> On Fri, Jul 24, 2009 at 12:31:02PM +1200, Aaron Robinson wrote:
> > if I set the value of a blob column by setting a
> > varialbe on my object, it gets written to the db just fine, but when I do
> it
> > inside a transaction using sqlbuilder I have the error. Please see the
> code
> > below.
> >
> > Test Code:
> >
> > from sqlobject import *
> > from array import *
> >
> > sqlhub.processConnection =
> connectionForURI('postgres://user:pass@localhost
> > /mydb')
> >
> > class MyObject(SQLObject):
> >     myInt =  IntCol(default=42)
> >     myBlob = BLOBCol(default=None)
> >
> > MyObject.createTable()
> >
> > #This works:
> > myObject = MyObject()
> > myObject.myInt = 43
> > myObject.myBlob = array('H',range(256)).tostring()
>
>    I hope you know you can set many values at once:
> myObject.set(myInt=43, myBlob=array('H',range(256)).tostring())
>   (That's offtopic, just a reminder.)
>
> > #This doesn't work:
> > record = {'my_int':44, 'my_blob':array('H',range(256)).tostring()}
> > conn = sqlhub.getConnection()
> > tx = conn.transaction()
> > tx.query(conn.sqlrepr(sqlbuilder.Insert(MyObject, [record])))
> > tx.commit()
> >
> > #psycopg2.DataError: invalid byte sequence for encoding "UTF8": 0x80
> > #HINT:  This error can also happen if the byte sequence does not match
> the
> > encoding expected by the server, which is controlled by
> "client_encoding".
>
>    First, this has nothing with transactions. You can do conn.query() here.
> Second, SQLBuilder... SQLObject is a high-level object that does a lot of
> things internally, but SQLBuilder is a low-level interface that knows
> nothing about classes, columns, column types, conversion; the first
> parameters should be string (table name), the values must be converted to
> the DB format; for a BLOB it means you have to use psycopg.Binary wrapper.
>   This code works for my in Postgres and SQLite:
>
> record = {'my_int':44,
> 'my_blob':conn.createBinary(array('H',range(256)).tostring())}
> conn.query(conn.sqlrepr(sqlbuilder.Insert(MyObject.sqlmeta.table,
> [record])))
>
> Oleg.
> --
>     Oleg Broytmann            http://phd.pp.ru/            ph...@ph...
>           Programmers don't die, they just GOSUB without RETURN.
>