RE : [Pypgsql-users] Binary data with postgress

[Mignon, L. <MignonL@PCF.BE>]

If I understood all what you say, the best thing to do is waiting the =
next
release of pypgsql to be sure that the related bug is fixed!=20
Before this release, all test that I do on retrieved data must be done =
on
the value member of PgBytea class.

Thanks for your help!

-----Message d'origine-----
De=A0: Billy G. Allie [mailto:Bil...@mu...]=20
Envoy=E9=A0: mardi 26 novembre 2002 7:40
=C0=A0: Mignon, Laurent; 'pyp...@li...';
ger...@gm...
Objet=A0: Re: [Pypgsql-users] Binary data with postgress=20

Gerhard =3D?iso-8859-1?Q?H=E4ring?=3D wrote:
> I was trying to answer this question, too. In the process of which I =
was
> constructing an example using BYTEA. Unfortunately, there seems to be =
a
> bug in pyPgSQL that we should eliminate before (finally, *cough*)
> releasing 2.3:
>=20
> # Database schema used:
> # create table test(ba bytea, lo oid);
>=20
> from pyPgSQL import PgSQL
>=20
> bindata =3D "".join([chr(x) for x in range(256)] * 10)
>=20
> con =3D PgSQL.connect()
>=20
> cursor =3D con.cursor()
>=20
> # I) BYTEA
>=20
> # Storing BYTEA:
> cursor.execute("insert into test(ba) values (%s)",
(PgSQL.PgBytea(bindata),))
> last_oid =3D cursor.oidValue
>=20
> # Retrieving BYTEA
> cursor.execute("select ba from test where oid=3D%s", (last_oid,))
> row =3D cursor.fetchone()
>=20
> # Check if input is the same as output
> assert bindata =3D=3D row.ba
>=20
> con.close()
>=20
>=20
> It looks like the quoting of BYTEAs is wrong, at least when the BYTEA
> starts with a chr(0). But I haven't got a real clue where the problem
> lies. Though I vaguely remember touching that piece of code once when =
I
> was working on the ARRAY stuff. I hope I didn't introduce the bug =
then
> *blush*.

Gerhard,

The problem is with the PgBytea class. It is missing the hidden methods =
for=20
determining length, comparisons, concatenation (+), repetition (*), =
etc.  I=20
will be very happy when version 3.0 gets out the door and we can just=20
sub-class the string object :-)  I will fix the class by this weekend.

>>> from pyPgSQL import PgSQL
>>> a =3D '\000ab\000'  # Create a string with NUL characters in it.
>>> len(a)
4
>>> a
'\x00ab\x00'
>>> PgSQL.PgQuoteBytea(a)  # Check how it's quoted by pyPgSQL
"'\\\\000ab\\\\000'"
>>> cx =3D PgSQL.connect()   # Lets put it into the database
>>> cu =3D cx.cursor()
>>> cu.execute('create table byteatest (a bytea, b oid)')
>>> cx.commit()
>>> cu.execute('insert into byteatest values(%s, %s)', =
PgSQL.PgBytea(a), 0)
>>> cx.commit()
>>> cu.execute('select * from byteatest')
>>> rs =3D cu.fetchone()
>>> rs
['\x00ab\x00', 0]
>>> cu.execute('insert into byteatest(a) values(%s)', PgSQL.PgBytea(a))
>>> cx.commit()
>>> cu.execute('select * from byteatest');
>>> rs =3D cu.fetchall()
>>> for i in rs:
..     print i
..=20
['\x00ab\x00', 0]
['\x00ab\x00', None]
>>> cu.execute('insert into byteatest(a) values(%s)', =
(PgSQL.PgBytea(a),))
>>> cx.commit()
>>> cu.execute('select * from byteatest');
>>> rs =3D cu.fetchall()
>>> for i in rs:
..     print i
..=20
['\x00ab\x00', 0]
['\x00ab\x00', None]
['\x00ab\x00', None]
>>> len(rs[0].a)	# len() doesn't work on PgBytea types
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: PgBytea instance has no attribute '__len__'
>>> len(rs[0].a.value)
4
>>> assert a =3D=3D rs[0].a  # Comparison doesn't work either
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AssertionError
>>> assert a =3D=3D rs[0].a.value
>>>

--=20
____       | Billy G. Allie    | Domain....: Bil...@mu...
|  /|      | 7436 Hartwell     | MSN.......: B_G...@em...
|-/-|----- | Dearborn, MI 48126|
|/  |LLIE  | (313) 582-1540    |



--=20
____       | Billy G. Allie    | Domain....: Bil...@mu...
|  /|      | 7436 Hartwell     | MSN.......: B_G...@em...
|-/-|----- | Dearborn, MI 48126|
|/  |LLIE  | (313) 582-1540    |