On 8/23/15 8:17 AM, Alex Fraser wrote:
I'm using the separate table versioning code from /history_meta.py/.
When I try to save a new object, I get this:
|
[...]
File"/usr/local/lib/python3.4/dist-packages/sqlalchemy/orm/session.py",line
1282,in_autoflush
self.flush()
File"/usr/local/lib/python3.4/dist-packages/sqlalchemy/orm/session.py",line
2004,inflush
self._flush(objects)
File"/usr/local/lib/python3.4/dist-packages/sqlalchemy/orm/session.py",line
2031,in_flush
self.dispatch.before_flush(self,flush_context,objects)
File"/usr/local/lib/python3.4/dist-packages/sqlalchemy/event/attr.py",line
218,in__call__
fn(*args,**kw)
File"/usr/share/foo/app/server/history_meta.py",line 290,inbefore_flush
create_version(obj,session)
File"/usr/share/foo/app/server/history_meta.py",line 256,increate_version
attr[hist_col.key]=a[0]
IndexError:tuple index outof range
|
I added some logging, and it seems that this happens for attributes
that I haven't assigned a value to, and which have a default value of
/None/. - because in this line in /create_version/, /a/, /u/ and /d/
are all empty:
|
a,u,d =attributes.get_history(obj,prop.key)
|
If I actually assign /None/ to the attribute before saving, then it
works fine. It also works if I apply this patch to /history_meta.py/:
|
diff --git a/src/app/server/history_meta.py
b/src/app/server/history_meta.py
index 02b54e0..17cd87f100644
---a/src/app/server/history_meta.py
+++b/src/app/server/history_meta.py
@@-240,10+240,13@@defcreate_version(obj,session,deleted=False):
obj_changed =True
elifu:
attr[hist_col.key]=u[0]
-else:
+elifa:
# if the attribute had no value.
attr[hist_col.key]=a[0]
obj_changed =True
+else:
+# The attribute has never had a value
+ attr[hist_col.key]=None
ifnotobj_changed:
# not changed, but we have relationships. OK
|
Is this a reasonable thing to do?
yes and no. Yes, if there's no "added" history, that should be skipped
as you're doing, but no in that that particular line of code is not
called if an object is being saved for the first time, only on an
update, and then only if that attribute actually had a change, which you
are saying this attribute did not.
so if you can please share: 1. a mapping and an exact usage that
illustrates how this is happening 2. what exact version of SQLAlchemy
are you using and 3. have you modified the history_meta.py recipe in any
way?
Cheers,
Alex
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