On Wed, Jan 8, 2020 at 2:38 PM Velu Narasimman <[email protected]> wrote:
>
> Hi,
>
> I am using MenusPlugin for displaying trac menus as submenus. At one
> point of implementation we are trying to store a list of dictionary of data
> that is generated by this menus plugin into postgresql database. Please find
> the list of dictionary sample below.
>
>
> [{'parent_name': u'top', 'href': u'/auth/dashboard', 'name': u'new_dash',
> 'active': False, 'visited': True, 'enabled': True, u'order': u'-9999999',
> 'label': <Fragment>}, {'parent_name': u'top', 'href': u'/myprojects', 'name':
> u'allprojects', 'active': True, 'visited': True, 'enabled': True, u'order':
> u'-9999998', 'label': <Fragment>}, {'parent_name': u'top', 'href': u'#',
> 'name': u'alltimesheet', 'children': <Element "ul">, 'active': False,
> 'visited': True, 'enabled': True, u'order': u'-9999997', 'label':
> <Fragment>}, {'parent_name': u'top', 'href': u'/myteam', 'name': u'myteam',
> 'children': <Element "ul">, 'active': False, 'visited': True, 'enabled':
> True, u'order': u'-9999996', 'label': <Fragment>}, {'name': u'timesheet',
> 'parent_name': u'top', 'enabled': True, 'label': <Fragment>, 'children':
> <Element "ul">, 'href': '#', 'active': False, 'visited': True, u'order':
> u'4'}, {'parent_name': 'top', 'name': u'admin', 'enabled': False, 'label':
> <Fragment>, 'href': '#', 'active': False, 'visited': True, u'order':
> u'999999'}, {'name': u'username', 'parent_name': u'top', 'enabled': True,
> 'label': <Fragment>, 'children': <Element "ul">, 'href': '#', 'active':
> False, 'visited': True, u'order': u'9999999'}]
>
> My aim is to store this whole list of dictionary into a table as is. But as
> you can see some Genshi <fragment> and <Element "ul"> are present in this,
> following two methods are failing.
>
> 1. Pickle object
> 2. Json
>
> Method 1: (Pickle)
> -------------------------
> pickle_data = cPickle.dumps(menu_dict, -1) # menu_dict is the data that you
> can see above.
> # constructed pickle successfully
> in this step.
> binary_menu = psycopg2.Binary(pickle_data) # converting pickle to Binary is
> also done successfully.
> # And I hope I can store this data
> to db as is but for a try I am unpickling the
> # binary data back to it's original form using the below
> statement
> # and that doesn't work!
> cPickle.loads(str(binary_menu)) # this throws some errors as shown below.
>
>
> Below is the error that I ended up with the last line in above chunk
>
>
> Trac detected an internal error:
>
>
> UnpicklingError: invalid load key, '''.
psycopg2.Binary is wrapper class for binary in PostgreSQL and to
generate binary literal.
That instance is unable to use to cPickle.loads.
>>> import cPickle
>>> data = cPickle.dumps({'key':42})
>>> data
"(dp1\nS'key'\np2\nI42\ns."
>>> psycopg2.Binary(data)
<psycopg2._psycopg.Binary object at 0x2abca30>
>>> print(str(psycopg2.Binary(data)))
'(dp1\012S''key''\012p2\012I42\012s.'::bytea
>>> str(psycopg2.Binary(data))
"'(dp1\\012S''key''\\012p2\\012I42\\012s.'::bytea"
A buffer instance in psycopg2 is retrieved from a binary column.
It is able to cPickle.loads from the buffer instance.
>>> from trac.env import Environment
>>> env = Environment('/var/lib/trac/1.0-postgres')
>>> rows = env.db_query('SELECT %s', (psycopg2.Binary(data),))
>>> rows[0][0]
<read-only buffer for 0x2df81d0, size 21, offset 0 at 0x2ebdc70>
>>> str(rows[0][0])
"(dp1\nS'key'\np2\nI42\ns."
>>> cPickle.loads(str(rows[0][0]))
{'key': 42}
--
Jun Omae <[email protected]> (大前 潤)
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