Re: [sqlalchemy] ConcurrentModificationError: Deleted rowcount 0 ... but only on mysql?
On Aug 21, 2010, at 7:45 AM, Ergo wrote: ConcurrentModificationError: Deleted rowcount 0 does not match number of objects deleted... for clarity, this error has been renamed to StaleDataError.Here is the docstring coming up in 0.6.4: * A flush may have attempted to update or delete rows and an unexpected number of rows were matched during the UPDATE or DELETE statement. Note that when version_id_col is used, rows in UPDATE or DELETE statements are also matched against the current known version identifier. * A mapped object with version_id_col was refreshed, and the version number coming back from the database does not match that of the object itself. I create my schema from models using create_all() - now , the problem is i get this error only using mysql or mysql+oursql. It happens every time in one place of my code. We have tests for cursor.rowcount that pass fully using OurSQL. Have you tried MySQL-python just to check that its not an OurSQL issue ,perhaps a newer or older version of OurSQL we haven't tested against is in use ?We would need code + oursql version that illustrates the issue being reproduced. But when i uses postgresql nothing bad happens and that exactly same code and same models work without issues. Is it possible im hitting a bug in sa here i did something wrong? Normally i would just assume i did some mistake when mapping models, but on postgresql it works like a charn... im a bit lost -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] ConcurrentModificationError
On Dec 2, 2009, at 5:46 PM, Dave Paola wrote:
I'm getting this: ConcurrentModificationError: updated rowcount 0 does not
match number of objects updated 1 when I try to commit a simple deletion.
I'm using Sqlite locally but the error also occurs on a Postgres database in
a live environment with only ONE user connected.
I saw this post from Nov. 11th:
http://groups.google.com/group/sqlalchemy/browse_thread/thread/e7175c7351963128
but because I'm not doing any copying (just deletion), it didn't seem to
provide anything useful. Both session.dirty and session.new are empty.
I have a Task class mapped to an association table called TaskTag that has a
task_id and tag_id. I'm literally doing a session.delete(task) followed by a
session.commit() and session.close(). Here's my mapper:
mapper(Task, tasks_table, properties = {
'tags' : relation(Tag, secondary=tasktags_table, lazy =
False)
})
I suspect this has something to do with the many-to-many relationship, but
for the life of me I cannot figure out what's going on. Thanks in advance.
this can happen if you have tasktags_table explicitly mapped elsewhere.the
mapper for tasktags_table will issue a DELETE, and then if Task.tags is also
modified in some way that affects the same row, the DELETE issued corresponding
to the relation() will not find its row.In that case the Concurrent name
is referring to two different configurations within a single flush conflicting
with each other. If this is your issue, strategies to address include placing
viewonly=True on the relation() or using the association proxy pattern (you can
even use both if you want to pick and choose how the SQL to load records is
emitted).
P.S. I use SqlAlchemy so often, I love the framework. Thanks to everyone for
your hard work, it's greatly appreciated :-)
The compliments are appreciated !
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Re: [sqlalchemy] ConcurrentModificationError
Indeed, I do have TaskTags mapped to it's own class. However, I never
explicitly delete any TaskTag object, only create them.
In any case, what would the preferred way to add a new tag to a task (a new
entry in the association table)? I was using the ORM to just create a new
instance of TaskTag (the mapped class). If having the association table
mapped to its own class becomes problematic, what's the convention for
accomplishing this?
Thanks for your feedback :-)
-Dave
On Wed, Dec 2, 2009 at 4:58 PM, Michael Bayer mike...@zzzcomputing.comwrote:
On Dec 2, 2009, at 5:46 PM, Dave Paola wrote:
I'm getting this: ConcurrentModificationError: updated rowcount 0 does not
match number of objects updated 1 when I try to commit a simple deletion.
I'm using Sqlite locally but the error also occurs on a Postgres database
in a live environment with only ONE user connected.
I saw this post from Nov. 11th:
http://groups.google.com/group/sqlalchemy/browse_thread/thread/e7175c7351963128but
because I'm not doing any copying (just deletion), it didn't seem to
provide anything useful. Both session.dirty and session.new are empty.
I have a Task class mapped to an association table called TaskTag that has
a task_id and tag_id. I'm literally doing a session.delete(task) followed
by a session.commit() and session.close(). Here's my mapper:
mapper(Task, tasks_table, properties = {
'tags' : relation(Tag, secondary=tasktags_table, lazy =
False)
})
I suspect this has something to do with the many-to-many relationship, but
for the life of me I cannot figure out what's going on. Thanks in advance.
this can happen if you have tasktags_table explicitly mapped elsewhere.
the mapper for tasktags_table will issue a DELETE, and then if Task.tags is
also modified in some way that affects the same row, the DELETE issued
corresponding to the relation() will not find its row.In that case the
Concurrent name is referring to two different configurations within a
single flush conflicting with each other. If this is your issue, strategies
to address include placing viewonly=True on the relation() or using the
association proxy pattern (you can even use both if you want to pick and
choose how the SQL to load records is emitted).
P.S. I use SqlAlchemy so often, I love the framework. Thanks to everyone
for your hard work, it's greatly appreciated :-)
The compliments are appreciated !
--
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Re: [sqlalchemy] ConcurrentModificationError
Dave Paola wrote:
Indeed, I do have TaskTags mapped to it's own class. However, I never
explicitly delete any TaskTag object, only create them.
In any case, what would the preferred way to add a new tag to a task
(a new entry in the association table)? I was using the ORM to just
create a new instance of TaskTag (the mapped class). If having the
association table mapped to its own class becomes problematic, what's
the convention for accomplishing this?
Thanks for your feedback :-)
(I'm about 80% sure this paragraph is correct, so take it with a grain
of salt).
I'm guessing you also have a relation from Task to TaskTags (e.g.
Task.task_tags). By default, many-to-many relations will cascade the
delete to the the secondary table (so the Task.tags relation cascades
DELETEs to tasktags_table), and one-to-many relations will set foreign
key columns to NULL on the related table (so the Task.task_tags relation
cascades UPDATEs to tasktags_table). Add this all up and SQLAlchemy will
try to UPDATE a deleted row or DELETE an updated row, depending on which
cascade happens first. A similar situation occurs if the Task.task_tags
relation has cascade=delete set (SQLAlchemy would try to DELETE a
deleted row).
Usually a table like tasktags_table has no columns except for foreign
keys to the related tables (e.g. task_id and tag_id columns). If this is
the case for your tasktags_table table, you probably don't want to map
it at all: just use it as a secondary table in the relation.
Otherwise, I would recommend the association_proxy method over the
viewonly=True method, because the viewonly=True method leaves a lot of
room for things to get out of sync until you commit or expire the
session. To use the association_proxy, try this:
from sqlalchemy.ext.associationproxy import association_proxy
mapper(Task, tasks_table, properties = {
# Assumes you have a TaskTag.tag relation.
'tags' : association_proxy(
'task_tags',
'tag',
creator=lambda tag: TaskTag(tag=tag)),
'task_tags': relation(TaskTag, lazy=False)
})
You only need the creator argument if you want to create TaskTag objects
implicitly, e.g. my_task.tags.append(my_tag). I'm also guessing your
TaskTag constructor accepts a tag keyword parameter.
Hope it helps,
-Conor
On Wed, Dec 2, 2009 at 4:58 PM, Michael Bayer
mike...@zzzcomputing.com mailto:mike...@zzzcomputing.com wrote:
On Dec 2, 2009, at 5:46 PM, Dave Paola wrote:
I'm getting this: ConcurrentModificationError: updated rowcount 0
does not match number of objects updated 1 when I try to commit a
simple deletion. I'm using Sqlite locally but the error also
occurs on a Postgres database in a live environment with only ONE
user connected.
I saw this post from Nov.
11th:
http://groups.google.com/group/sqlalchemy/browse_thread/thread/e7175c7351963128
but because I'm not doing any copying (just deletion), it didn't
seem to provide anything useful. Both session.dirty and
session.new are empty.
I have a Task class mapped to an association table called TaskTag
that has a task_id and tag_id. I'm literally doing a
session.delete(task) followed by a session.commit() and
session.close(). Here's my mapper:
mapper(Task, tasks_table, properties = {
'tags' : relation(Tag, secondary=tasktags_table,
lazy = False)
})
I suspect this has something to do with the many-to-many
relationship, but for the life of me I cannot figure out what's
going on. Thanks in advance.
this can happen if you have tasktags_table explicitly mapped
elsewhere.the mapper for tasktags_table will issue a DELETE,
and then if Task.tags is also modified in some way that affects
the same row, the DELETE issued corresponding to the relation()
will not find its row.In that case the Concurrent name is
referring to two different configurations within a single flush
conflicting with each other. If this is your issue, strategies to
address include placing viewonly=True on the relation() or using
the association proxy pattern (you can even use both if you want
to pick and choose how the SQL to load records is emitted).
P.S. I use SqlAlchemy so often, I love the framework. Thanks to
everyone for your hard work, it's greatly appreciated :-)
The compliments are appreciated !
--
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