sqlobject-discuss

[SQLObject] SQLObject and Zope 2.7.3/2.8.0a1

[Anders B. O. <an...@br...>]

Hi,

I realize that this question may have been brought up before, but I
haven't been able to find a good answer in the archives.

I am trying to make a Zope product that uses SQLObject to talk to a
MySQL database. In my main class (SimpleItem) I have a method called
listPeople() which looks like this:

def listPeople(self):
    """Return a list of people"""
    p = Backend.People.select(Backend.People.q.entity == 0)
    people = list()
    for person in list(p):
        people.append({"id": person.id, "name": person.name, "lived": person.lived})
    return people

It is called from a ZPT file to get a list of authors (it's a book
database) that can be displayed.

It works fine right after being added, but after refreshing the product
or restarting the Zope server, I get this error whenever I try to view a
page that calls that method:

Error Type: AttributeError
Error Value: 'NoneType' object has no attribute 'iterSelect'

According to the errorlog the error occurs on the line where I do the
for-loop, which means that the problem is the list(p) call. I am
guessing that this is due to persistence or something like that. I
thought it might be something related to cache, so I tried setting
_cacheValues = False on the Backend.People class, but that didn't change
anything.

Can anybody help?
Is it just 100% impossible to use SQLObject with Zope 2?
I have tried this with both Zope 2.7.3 and 2.8.0a1 with the same
results.

-- 
Anders
-----BEGIN GEEK CODE BLOCK-----
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Re: [SQLObject] SQLObject and Zope 2.7.3/2.8.0a1

[Oleg B. <ph...@ma...>]

On Fri, Nov 26, 2004 at 08:53:32AM +0100, Anders Bruun Olsen wrote:
> def listPeople(self):
>     """Return a list of people"""
>     p = Backend.People.select(Backend.People.q.entity == 0)
>     people = list()

   Why not
    people = []
   ?

>     for person in list(p):
>         people.append({"id": person.id, "name": person.name, "lived": person.lived})
>     return people
> 
> It is called from a ZPT file to get a list of authors (it's a book
> database) that can be displayed.
> 
> It works fine right after being added, but after refreshing the product
> or restarting the Zope server, I get this error whenever I try to view a
> page that calls that method:
> 
> Error Type: AttributeError
> Error Value: 'NoneType' object has no attribute 'iterSelect'
> 
> According to the errorlog the error occurs on the line where I do the
> for-loop, which means that the problem is the list(p) call. I am

   No. .select() cannot find a module or class.

> guessing that this is due to persistence or something like that. I

   No, this is due to problems with registries. SQLObject registries are
not compatible with module reloading (refresh).

> Is it just 100% impossible to use SQLObject with Zope 2?

   It is possible, at least in Zope3. Look at
http://codespeak.net/z3/sqlos/ . May be you can port it to Zope2.

Oleg.
-- 
     Oleg Broytmann            http://phd.pp.ru/            ph...@ph...
           Programmers don't die, they just GOSUB without RETURN.

Re: [SQLObject] SQLObject and Zope 2.7.3/2.8.0a1

[Anders B. O. <an...@br...>]

On Fri, Nov 26, 2004 at 12:32:31PM +0300, Oleg Broytmann wrote:
> >     people = list()
>    Why not
>     people = []
>    ?

Readability. I like list() because it seems just a tiny bit more clear
than [], even though the end result is the same.

> > According to the errorlog the error occurs on the line where I do the
> > for-loop, which means that the problem is the list(p) call. I am
>    No. .select() cannot find a module or class.

Ahh.. and .select() returns None, and the list(p) then fails because
list(None) does not make sense, since None is not iterable.

> > guessing that this is due to persistence or something like that. I
>    No, this is due to problems with registries. SQLObject registries are
> not compatible with module reloading (refresh).

Hmm.. and I assume there is no easy way to fix that?

> > Is it just 100% impossible to use SQLObject with Zope 2?
>    It is possible, at least in Zope3. Look at
> http://codespeak.net/z3/sqlos/ . May be you can port it to Zope2.

It looks really good, but I doubt that I can easily port it to Zope2,
and Zope3 looks like quite a different beast than Zope2.
I might end up having to just deal with SQL directly :(

-- 
Anders
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GCS/O d--@ s:+ a-- C++ UL+++$ P++ L+++ E- W+ N(+) o K? w O-- M- V
PS+ PE@ Y+ PGP+ t 5 X R+ tv+ b++ DI+++ D+ G e- h !r y?
------END GEEK CODE BLOCK------
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Re: [SQLObject] SQLObject and Zope 2.7.3/2.8.0a1

[Oleg B. <ph...@ma...>]

On Fri, Nov 26, 2004 at 12:26:45PM +0100, Anders Bruun Olsen wrote:
> On Fri, Nov 26, 2004 at 12:32:31PM +0300, Oleg Broytmann wrote:
> > >     people = list()
> >    Why not
> >     people = []
> >    ?
> 
> Readability. I like list() because it seems just a tiny bit more clear
> than [], even though the end result is the same.

   Oops. My readability taste says opposite! :) I prefer [] to list().
The matter of taste...

> > > According to the errorlog the error occurs on the line where I do the
> > > for-loop, which means that the problem is the list(p) call. I am
> >    No. .select() cannot find a module or class.
> 
> Ahh.. and .select() returns None, and the list(p) then fails because
> list(None) does not make sense, since None is not iterable.

   Clear, but not exactly. .select() returns SelectResult, whose
__iter__ returns iterSelect of its dbconnection. It seems connection
object was broken or lost during refresh.

> > > guessing that this is due to persistence or something like that. I
> >    No, this is due to problems with registries. SQLObject registries are
> > not compatible with module reloading (refresh).
> 
> Hmm.. and I assume there is no easy way to fix that?

   Do not use refresh. Always do full Zope restart - stop and start it
anew.

Oleg.
-- 
     Oleg Broytmann            http://phd.pp.ru/            ph...@ph...
           Programmers don't die, they just GOSUB without RETURN.

Re: [SQLObject] SQLObject and Zope 2.7.3/2.8.0a1

[Anders B. O. <an...@br...>]

On Fri, Nov 26, 2004 at 02:36:07PM +0300, Oleg Broytmann wrote:
> > Readability. I like list() because it seems just a tiny bit more clear
> > than [], even though the end result is the same.
>    Oops. My readability taste says opposite! :) I prefer [] to list().
> The matter of taste...

Yup! :)

> > Ahh.. and .select() returns None, and the list(p) then fails because
> > list(None) does not make sense, since None is not iterable.
>    Clear, but not exactly. .select() returns SelectResult, whose
> __iter__ returns iterSelect of its dbconnection. It seems connection
> object was broken or lost during refresh.

Okay.

> > >    No, this is due to problems with registries. SQLObject registries are
> > > not compatible with module reloading (refresh).
> > Hmm.. and I assume there is no easy way to fix that?
>    Do not use refresh. Always do full Zope restart - stop and start it
> anew.

Same problem. Whenever Zope has been stopped my product breaks as I have
described, and it needs to be added again. I have tried with "Restart"
in the Zope panel and actually stopping the Zope service on the server
and starting it again.

-- 
Anders
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GCS/O d--@ s:+ a-- C++ UL+++$ P++ L+++ E- W+ N(+) o K? w O-- M- V
PS+ PE@ Y+ PGP+ t 5 X R+ tv+ b++ DI+++ D+ G e- h !r y?
------END GEEK CODE BLOCK------
PGPKey: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x8BFECB41

Re: [SQLObject] SQLObject and Zope 2.7.3/2.8.0a1

[Oleg B. <ph...@ma...>]

On Fri, Nov 26, 2004 at 04:54:14PM +0100, Anders Bruun Olsen wrote:
> >    Do not use refresh. Always do full Zope restart - stop and start it
> > anew.
> 
> Same problem. Whenever Zope has been stopped my product breaks as I have
> described, and it needs to be added again. I have tried with "Restart"
> in the Zope panel and actually stopping the Zope service on the server
> and starting it again.

   Ouch! I am not sure about what caused this. My guess is that Zope or
ZODB cannot unpickle connection object. I am not sure if it is possible
to fix the problem. This is probably that "pickle problem" - SQLObject
tables are essentially non-picklable, I am afraid.

Oleg.
-- 
     Oleg Broytmann            http://phd.pp.ru/            ph...@ph...
           Programmers don't die, they just GOSUB without RETURN.

Re: [SQLObject] SQLObject and Zope 2.7.3/2.8.0a1

[Anders B. O. <an...@br...>]

On Fri, Nov 26, 2004 at 07:39:48PM +0300, Oleg Broytmann wrote:
> > Same problem. Whenever Zope has been stopped my product breaks as I have
> > described, and it needs to be added again. I have tried with "Restart"
> > in the Zope panel and actually stopping the Zope service on the server
> > and starting it again.
>    Ouch! I am not sure about what caused this. My guess is that Zope or
> ZODB cannot unpickle connection object. I am not sure if it is possible
> to fix the problem. This is probably that "pickle problem" - SQLObject
> tables are essentially non-picklable, I am afraid.

Damn.. oh well, I guess it's I'm gonna have to use the MySQLdb module
and do the SQL manually then :-/.
Since I was planning to first learn Zope and then get a Plone site up
and running for work and then integrate a few databases we have in there
through Zope/Plone products, it isn't just possible for me to use
something like Webware instead (which I believe I read somewhere runs
sqlobject just fine). I'll have to do the manual work for now since
Plone doesn't run on Zope3 yet and Zope3 seems quite a bit different
from Zope2.

Anyways, thank you for your help!

-- 
Anders
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GCS/O d--@ s:+ a-- C++ UL+++$ P++ L+++ E- W+ N(+) o K? w O-- M- V
PS+ PE@ Y+ PGP+ t 5 X R+ tv+ b++ DI+++ D+ G e- h !r y?
------END GEEK CODE BLOCK------
PGPKey: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x8BFECB41

Re: [SQLObject] SQLObject and Zope 2.7.3/2.8.0a1

[Anders B. O. <an...@br...>]

On Fri, Nov 26, 2004 at 07:39:48PM +0300, Oleg Broytmann wrote:
>    Ouch! I am not sure about what caused this. My guess is that Zope or
> ZODB cannot unpickle connection object. I am not sure if it is possible
> to fix the problem. This is probably that "pickle problem" - SQLObject
> tables are essentially non-picklable, I am afraid.

WHOA! It seems I fixed it!
I have in my Backend.py file not set a _connection for any of my
SQLObject classes because I want to define that information directly
when adding the object to Zope, and I then set it with
Backend.People.setConnection and so forth in my main class's __init__. I
thought I would give this one simply try to see if it was indeed just a
question of restoring the connection (and without knowing whether
sqlobject would indeed do what I thought it would do). I moved those
.setConnection calls into a method of it's own that is called from
__init__ but also from the methods that actually fetch information from
SQLObject right before instantiating any SQLObject classes, and it
bloody well survives both Zope restarts AND product refreshes now!
I know that it might be quite an evil punch in the gut of performance
for my app, but so far it is only a few people on our LAN that will use
it to interact with a few databases. Later when I need to integrate
those databases with a Plone site I can give some more consideration to
performance and see if it does indeed hurt performance to reconnect to
the db on every db-related-action.
Since most normal webapps do one db-connection per page load and this
will be almost the same I don't really think it will be that bad
performance-wise.

-- 
Anders
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GCS/O d--@ s:+ a-- C++ UL+++$ P++ L+++ E- W+ N(+) o K? w O-- M- V
PS+ PE@ Y+ PGP+ t 5 X R+ tv+ b++ DI+++ D+ G e- h !r y?
------END GEEK CODE BLOCK------
PGPKey: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x8BFECB41

Re: [SQLObject] SQLObject and Zope 2.7.3/2.8.0a1

[Oleg B. <ph...@ma...>]

On Fri, Nov 26, 2004 at 06:03:14PM +0100, Anders Bruun Olsen wrote:
> WHOA! It seems I fixed it!
[skip]
> Backend.People.setConnection and so forth in my main class's __init__. I

   Congratulations!

Oleg.
-- 
     Oleg Broytmann            http://phd.pp.ru/            ph...@ph...
           Programmers don't die, they just GOSUB without RETURN.