[ZODB-Dev] Getting refcount of object in ZODB

[Michel Pelletier]

Zope's control panel uses this code to show refcounts on the debug screen:

class Fake:
    def locked_in_version(self): return 0

class DebugManager: ...

    def refcount(self, n=None, t=(type(Fake), type(Acquisition.Implicit))):
        # return class reference info
        dict={}
        for m in sys.modules.values():
            for sym in dir(m):
                ob=getattr(m, sym)
                if type(ob) in t:
                    dict[ob]=sys.getrefcount(ob)
        pairs=[]
        append=pairs.append
        for ob, v in dict.items():
            if hasattr(ob, '__module__'):
                name='%s.%s' % (ob.__module__, ob.__name__)
            else: name='%s' % ob.__name__
            append((v, name))
        pairs.sort()
        pairs.reverse()
        if n is not None:
            pairs=pairs[:n]
        return pairs

This is just the normal in-memory refcounts.  Did you want to know about
references between persistent objects in the storage, even if deactivated?

-Michel

On Thu, 28 Jun 2001, Greg Ward wrote:

> On 28 June 2001, Barry A. Warsaw said:
> > There's no advertised storage API way of getting this information
> > AFAIK.  Different storages will maintain that information in different
> > ways (e.g. in Berkeley Full, it's maintained in a separate table --
> > well, two tables really, one for objects and the other for pickles ;).
> 
> So is GC entirely the storage's responsibility, then?  I.e., should I be
> poking about in FileStorage.py looking for rude back-door ways of
> getting the refcount?
> 
> Or should I just say: Jim, given DB/Connection/FileStorage objects and
> either an OID or database object, how do I get the refcount for the
> object?  And is that info available for ClientStorage as well?  Or will
> I have to shutdown my ZEO server and access the database as a
> FileStorage to find this out?
> 
> No, I do *not* intend to use this in an application, it's mainly
> curiosity.  I want to make sure that an object I think is about to drop
> to zero refs really does drop to zero refs.
> 
>         Greg
> 
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