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jonhattan | 1 Jul 2007 22:08
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who creates the related table in a RelatedJoin

Hi all,

I've found a problem I've hade the chance to circumvent it but would 
like to comment it out here in order to get some feedback.

the background (that will be a recipe in the wiki):

I use to use RelatedJoins to simulate one-to-many relations without the 
pain to add a foreignkey field for each relation.
Consider having a Telephone class and several clases that are naturally 
many-to-one related with telephone numbers. The tipical one-to-many 
aproach is:

class Telephone(SQLObject):
    number = StringCol()
    type = EnumCol(enumValues=['fax', 'line', 'movil'])
    person = ForeignKey('Person')
    entity = ForeignKey('Entity')

class Person(SQLObject):
    name = StringCol()
    t = MultipleJoin('Telephone')

class Entity(SQLObject):
    name = StringCol()
    t = MultipleJoin('Telephone')

So we have an ugly telephones table with two fk columns that should be 
mutually exclusive at a higher abstraction level than sql, but nothing 
constraints us to create a
(Continue reading)

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Oleg Broytmann | 1 Jul 2007 22:17
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Re: who creates the related table in a RelatedJoin

On Sun, Jul 01, 2007 at 09:08:39PM +0100, jonhattan wrote:
> So I have two questions.
> 
> first is, shouldn't it work with the last class definition I've shown?

   No, RelatedJoin was designed to be used symmetrically; you have to have
two RelatedJoins pointing to each other.

> second, could SQLObject create the table on first RelatedJoin it found, 
> instead of on the one resulting on applying the alphabetical sort?

   Currently no, but you can try to extend SQLObject. Patches (that work)
will be gladly accepted.

Oleg.
--

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     Oleg Broytmann            http://phd.pp.ru/            phd <at> phd.pp.ru
           Programmers don't die, they just GOSUB without RETURN.

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Humberto Diogenes | 4 Jul 2007 04:37
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Re: sqlite and threads - bug?

Hi, guys!

   I was just sending a new e-mail to the list when I saw this thread.
   I was having problems recently with sqlobject+sqlite in CherryPy  
and Apache (traceback attached), and noticed they started after a  
change from sqlobject.sqlite.sqliteconnection.SQLiteConnection (which  
was issuing deprecation warnings) to sqlobject.connectionForUri  
(recommended by those same warnings).
   Anyway, after I changed back to using the deprecated function it  
magically worked again.
   I then went to look at the source code, to see if there was  
anything different in connectionForURI. I saw that it tries to do  
some caching, and ends with this:

         #  <at>  <at> : Do we care if we clobber another connection?
         self.cachedURIs[uri] = conn
         return conn

   Can someone please tell me if connectionForURI is really doing  
what it was supposed to do?


Traceback (most recent call last):
  File "/usr/lib/python2.4/site-packages/cherrypy/_cphttptools.py", line 105, in _run
    self.main()
  File "/usr/lib/python2.4/site-packages/cherrypy/_cphttptools.py", line 254, in main
    body = page_handler(*virtual_path, **self.params)
  File "./servidor.py", line 275, in listar
    dados = [dict(documento_id=f.documento_id,
(Continue reading)

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Oleg Broytmann | 4 Jul 2007 09:08
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Re: sqlite and threads - bug?

On Tue, Jul 03, 2007 at 11:37:40PM -0300, Humberto Diogenes wrote:
>         #  <at>  <at> : Do we care if we clobber another connection?
>         self.cachedURIs[uri] = conn

   Does it help if you coment out this?

Oleg.
--

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

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Brian Cole | 4 Jul 2007 16:44
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Column name can not be the same as table name?

Hello All,

Just started using SQLObject yesterday, so if I made a rookie mistake
please tell me. It appears SQLObject doesn't allow me to have the same
column name as my table name. Here is the MySQL table definition:
CREATE TABLE `sysname` (
`sysname_id` int(11) NOT NULL auto_increment,
`sysname` varchar(64) NOT NULL,
PRIMARY KEY  (`sysname_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

And the corresponding SQLObject code:
class Sysname(SQLObject):
    class sqlmeta:
        fromDatabase = True
        idName = "sysname_id"

    def getSysnameID(cls):
        sysname = platform.system()
        for s in cls.selectBy(sysname=sysname):
            return s.id

        return cls(sysname=sysname).id
    getSysnameID = classmethod(getSysnameID)

print Sysname.getSysnameID()

I get the following traceback from SQLObject:
Traceback (most recent call last):
  File "knightly/machine.py", line 22, in ?
(Continue reading)

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Oleg Broytmann | 4 Jul 2007 17:50
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Re: Column name can not be the same as table name?

On Wed, Jul 04, 2007 at 08:44:15AM -0600, Brian Cole wrote:
> CREATE TABLE `sysname` (
> `sysname_id` int(11) NOT NULL auto_increment,
> `sysname` varchar(64) NOT NULL,
> PRIMARY KEY  (`sysname_id`)
> ) ENGINE=InnoDB DEFAULT CHARSET=utf8
> 
> '_SO_class_'+column.foreignKey).q.id
> TypeError: cannot concatenate 'str' and 'NoneType' objects

   I suspect SQLObject has problems getting column decriptions from the
database (due to fromDatabase). To start debugging print Sysname.sqlmeta.columns
- do they look right?

Oleg.
--

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

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bernhard.maeder | 5 Jul 2007 10:17
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Creating more sqlobjects in _create()

Hello all

I'm experiencing frequent deadlocks in my cherrypy/sqlobject multithreaded server application. I'm unable to reproduce the error in a small-scale example yet, but one thing I noticed is, that it might be related to me creating other sqlobjects in an overwritten _create() function.

What I see is that various threads try to acquire a threadSafeMethod decorator's lock, originating from various places:

...
File "/usr/lib/python2.4/site-packages/sqlobject/sresults.py", line 165, in __iter__
return iter(list(self.lazyIter()))
File "/usr/lib/python2.4/site-packages/sqlobject/dbconnection.py", line 804, in next
obj = self.select.sourceClass.get(result[0], selectResults=result[1:], connection=self.dbconn)
File "/usr/lib/python2.4/site-packages/sqlobject/main.py", line 915, in get
val = cls(_SO_fetch_no_create=1)
File "/usr/lib/python2.4/site-packages/sqlobject/declarative.py", line 92, in _wrapper
lock.acquire()
File "threading.py", line 100, in acquire
rc = self.__block.acquire(blocking)

And one thread is pending on the cache's lock:

...
File "/usr/lib/python2.4/site-packages/sqlobject/declarative.py", line 94, in _wrapper
return fn(self, *args, **kwargs)
File "/usr/lib/python2.4/site-packages/sqlobject/main.py", line 1214, in __init__
self._create(id, **kw)
File "/usr/lib/python2.4/site-packages/sqlobject/main.py", line 1245, in _create
self._SO_finishCreate(id)
File "/usr/lib/python2.4/site-packages/sqlobject/main.py", line 1271, in _SO_finishCreate
cache.created(id, self.__class__, self)
File "/usr/lib/python2.4/site-packages/sqlobject/cache.py", line 300, in created
self.caches[cls.__name__].created(id, obj)
File "/usr/lib/python2.4/site-packages/sqlobject/cache.py", line 177, in created
self.cull()
File "/usr/lib/python2.4/site-packages/sqlobject/cache.py", line 190, in cull
self.lock.acquire()

.. originating from a certain _create function (hence my assumption).

My create() is looking quite straight-forward, something like this:

class MyClass(sqlobject):
foo = ForeignKey('OtherClass', default=None)
bar = ForeignKey('OtherClass', default=None)

def _create(self, *args, **kw):
# Create the object
super(MyClass, self)._create(*args, **kw)

# Create other object
self.foo = OtherClass()
self.bar = OtherClass()

So, my question is: is this problematic, and, if yes, what other ways are there to do it?

Thanks a million
Bernhard


... and, sorry for the mess:
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Oleg Broytmann | 5 Jul 2007 10:55
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Re: Creating more sqlobjects in _create()

On Thu, Jul 05, 2007 at 10:17:31AM +0200, bernhard.maeder <at> zkb.ch wrote:
> I'm experiencing frequent deadlocks in my cherrypy/sqlobject multithreaded
> server application. I'm unable to reproduce the error in a small-scale
> example yet, but one thing I noticed is, that it might be related to me
> creating other sqlobjects in an overwritten _create() function.
> 
> What I see is that various threads try to acquire a threadSafeMethod
> decorator's lock, originating from various places:

   Are they different locks? And what are the error messages?

Oleg.
--

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

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bernhard.maeder | 5 Jul 2007 11:22
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Antwort: Re: Creating more sqlobjects in _create()

Hi Oleg, thanks for your response

> On Thu, Jul 05, 2007 at 10:17:31AM +0200, bernhard.maeder <at> zkb.ch wrote:
> > I'm experiencing frequent deadlocks in my cherrypy/sqlobject multithreaded
> > server application. I'm unable to reproduce the error in a small-scale
> > example yet, but one thing I noticed is, that it might be related to me
> > creating other sqlobjects in an overwritten _create() function.
> >
> > What I see is that various threads try to acquire a threadSafeMethod
> > decorator's lock, originating from various places:
>
>    Are they different locks?

I don't know, is there an easy way to tell? All I can see at the moment are the stack traces I have posted.

The accesses are made in different threads, to objects of the same class (MyClass in my example). One locks while resolving a ForeignKey in _SO_foreignKey(), one locks in _SO_finishCreate() and the third one in the selectresult's __iter__().

> And what are the error messages?

I have none, the application just locks. Or, more precisely: calls to sqlobject lock, while other parts of the application still work.

Bernhard

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Oleg Broytmann | 5 Jul 2007 11:31
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Re: Antwort: Re: Creating more sqlobjects in _create()

On Thu, Jul 05, 2007 at 11:22:36AM +0200, bernhard.maeder <at> zkb.ch wrote:
> The accesses are made in different threads, to objects of the same class
> (MyClass in my example). One locks while resolving a ForeignKey in
> _SO_foreignKey(), one locks in _SO_finishCreate() and the third one in the
> selectresult's __iter__().

   Can you do an experiment - create objects of OtherClass outside of
_create() and assign them to foreign keys after the object has been fully
created?

Oleg.
--

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

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