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Zac Medico wrote:
> I've implemented whiteouts so that items can now be deleted properly. The
> whiteouts themselves are stored inside the existing writable database
> (self.db_rw) in order to avoid the need for an additional storage area
> (similar to unionfs whiteouts which are implemented as hidden files).
>
> The whiteouts (if they exist) are validated on access and removed if
> necessary. A whiteout is considered invalid if it's _mtime_ and _eclasses_
> are not exactly equal to underlying database entry that it erases (or the
> underlying database entry no longer exists). This should cause whiteouts to
> be automatically invalidated whenever the underlying cache changes.
Here's a small patch to the previous module that compares the values given in a
_setitem call to the underlying db_ro in order to ensure that the writable
layer remains empty whenever possible.
Zac
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--- metadata_overlay.py.orig 2006-01-29 01:57:12.000000000 -0800
+++ metadata_overlay.py 2006-01-29 02:31:27.000000000 -0800
@@ -35,7 +35,17 @@
return value
def _setitem(self, name, values):
- self.db_rw[name] = values
+ try:
+ value_ro = self.db_ro[name]
+ if self._are_values_identical(value_ro,values):
+ # we have matching values in the underlying
db_ro
+ # so it is unnecessary to store data in db_rw
+ try:
+ del self.db_rw[name] # delete unwanted
whiteout when necessary
+ except KeyError:
+ pass
+ except KeyError:
+ self.db_rw[name] = values
def _delitem(self, cpv):
value = self[cpv] # validates whiteout and/or raises a KeyError
when necessary
@@ -71,8 +81,11 @@
def _is_whiteout_valid(self, name, value_rw):
try:
value_ro = self.db_ro[name]
- if long(value_rw["_mtime_"]) !=
long(value_ro["_mtime_"]):
- return False
- return value_rw["_eclasses_"] == value_ro["_eclasses_"]
+ return self._are_values_identical(value_rw,value_ro)
except KeyError:
return False
+
+ def _are_values_identical(self, value1, value2):
+ if long(value1["_mtime_"]) != long(value2["_mtime_"]):
+ return False
+ return value1["_eclasses_"] == value2["_eclasses_"]
