#10353: ZODB is basically useless in Sage, since it uses pickle protocol 1
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Reporter: was | Owner: jason
Type: defect | Status: new
Priority: major | Milestone: sage-4.6.1
Component: misc | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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{{{
wst...@sage:~$ /usr/local/bin/sage
----------------------------------------------------------------------
| Sage Version 4.6, Release Date: 2010-10-30 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
sage: d = sage.databases.db.Database('sage_zodb', read_only=False)
sage: d[12] = factor(12)
sage: d.commit()
...
TypeError: can't pickle SageObject objects
}}}
There is a zodb mailing list discussion related to the pickle protocol
here: http://www.mail-archive.com/[email protected]/msg04628.html
In particular, pickle protocol 1 is hardcoded. But SageObjects/Cython
objects must use protocol 2 in many cases:
{{{
sage: import cPickle
sage: F = factor(12)
sage: cPickle.dumps(F, protocol=0)
TypeError: can't pickle SageObject objects
sage: cPickle.dumps(F, protocol=1)
TypeError: can't pickle SageObject objects
sage: cPickle.dumps(F, protocol=2)
'\x80\x02csage.structure.factorization\nFactorization\nq\x01)\x81q\x02}q\x03(U\x12_Factorization__crq\x04\x89U\x14_Factorization__unitq\x05csage.rings.integer\nmake_integer\nq\x06U\x011\x85Rq\x07U\x18_Factorization__universeq\x08csage.rings.integer_ring\nIntegerRing\nq\t)Rq\nU\x11_Factorization__xq\x0b]q\x0c(h\x06U\x012\x85Rq\rK\x02\x86q\x0eh\x06U\x013\x85Rq\x0fK\x01\x86q\x10eub.'
}}}
There is some code in Sage that uses ZODB (e.g, Cremona database), but I
think it uses only pure python objects, so the above isn't a problem.
See also the related ticket #10352.
Some ideas for how to fix this:
- Modify ZODB itself, e.g., by changing: ZODB.serialiize.ObjectWriter as
suggested here: http://www.mail-archive.com/zodb-
[email protected]/msg04766.html
- Figure out how to monkeypatch ODB.serialiize.ObjectWriter at runtime,
then document this hack
- "Fix" SageObject and/or Cython, so Sage objects can serialize using
Pickle protocol 1 instead of requiring 2. I don't personally understand
exactly why SageObject can't be pickled using protocol 1.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10353>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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