[ZODB-Dev] BTrees and Mutables, was Re: [IndexedCatalog] bug in default indexing

[Casey Duncan]

On Tuesday 11 February 2003 04:57 pm, Casey Duncan wrote:
> On Tuesday 11 February 2003 04:04 pm, Christian Reis wrote:
> > On Tue, Feb 11, 2003 at 03:24:05PM -0500, Shane Hathaway wrote:
> > > Casey Duncan wrote:
> > > > An alternative which is perhaps more palatable is to just set the=
=20
whole=20
> > > > mutable object into the btree again. Like:
> > > >=20
> > > > l =3D tree['bar']
> > > > l.append(4)
> > > > tree['bar'] =3D l # Trigger list persistance
> > >=20
> > > In fact, if you put simple lists in BTrees, you have to use this=20
> > > pattern.  Setting tree._p_changed will not get the right object sto=
red.=20
> >=20
> > Whoa. You mean to say that:
> >=20
> >     l =3D tree['bar']
> >     l.append(4)
> >     tree['bar'] =3D l
> >=20
> > is *not* the same as:
> >=20
> >     tree['bar'].append(4)
> >=20
> > right? And the first form *does* work as expected, or are there
> > side-effects?
>=20
> The side affect is that the new list value is persisted. Otherwise it i=
sn't=20
> (as in the 2nd example) and the next time it is loaded from the databas=
e the=20
> list will not contain 4.
>=20
> As Shane mentioned, you probably should store non-persistent mutable ob=
jects=20
> in BTrees at all.

Oops that should read:

you probably should not store non-persistent mutable objects in BTrees at=
 all.