Reimplemented DemoStorage to be just a wrapper around a base storage

and a changes storage.

src/ZODB/DemoStorage.test

+DemoStorage demo (doctest)
+--------------------------
+
+Note that most people will configure the storage through ZConfig.  If
+you are one of those people, you may want to stop here. :)  The
+examples below show you how to use the storage from Python, but they
+also exercise lots of details you might not be interested in.
+
+To see how this works, we'll start by creating a base storage and
+puting an object (in addition to the root object) in it:
+
+    >>> from ZODB.FileStorage import FileStorage
+    >>> base = FileStorage('base.fs')
+    >>> from ZODB.DB import DB
+    >>> db = DB(base)
+    >>> from persistent.mapping import PersistentMapping
+    >>> conn = db.open()
+    >>> conn.root()['1'] = PersistentMapping({'a': 1, 'b':2})
+    >>> import transaction
+    >>> transaction.commit()
+    >>> db.close()
+    >>> import os
+    >>> original_size = os.path.getsize('base.fs')
+
+Now, lets reopen the base storage in read-only mode:
+
+    >>> base = FileStorage('base.fs', read_only=True)
+
+And open a new storage to store changes:
+
+    >>> changes = FileStorage('changes.fs')
+
+and combine the 2 in a demofilestorage:
+
+    >>> from ZODB.DemoStorage import DemoStorage
+    >>> storage = DemoStorage(base=base, changes=changes)
+
+If there are no transactions, the storage reports the lastTransaction
+of the base database:
+
+    >>> storage.lastTransaction() == base.lastTransaction()
+    True
+
+Let's add some data:
+
+    >>> db = DB(storage)
+    >>> conn = db.open()
+    >>> items = conn.root()['1'].items()
+    >>> items.sort()
+    >>> items
+    [('a', 1), ('b', 2)]
+
+    >>> conn.root()['2'] = PersistentMapping({'a': 3, 'b':4})
+    >>> transaction.commit()
+
+    >>> conn.root()['2']['c'] = 5
+    >>> transaction.commit()
+
+Here we can see that we haven't modified the base storage:
+
+    >>> original_size == os.path.getsize('base.fs')
+    True
+
+But we have modified the changes database:
+
+    >>> len(changes)
+    2
+
+Our lastTransaction reflects the lastTransaction of the changes:
+
+    >>> storage.lastTransaction() > base.lastTransaction()
+    True
+
+    >>> storage.lastTransaction() == changes.lastTransaction()
+    True
+
+Let's walk over some of the methods so ewe can see how we delegate to
+the new underlying storages:
+
+    >>> from ZODB.utils import p64, u64
+    >>> storage.load(p64(0), '') == changes.load(p64(0), '')
+    True
+    >>> storage.load(p64(0), '') == base.load(p64(0), '')
+    False
+    >>> storage.load(p64(1), '') == base.load(p64(1), '')
+    True
+
+    >>> serial = base.getTid(p64(0))
+    >>> storage.loadSerial(p64(0), serial) == base.loadSerial(p64(0), serial)
+    True
+
+    >>> serial = changes.getTid(p64(0))
+    >>> storage.loadSerial(p64(0), serial) == changes.loadSerial(p64(0),
+    ...                                                          serial)
+    True
+
+The object id of the new object is quite random, and typically large:
+
+    >>> print u64(conn.root()['2']._p_oid)
+    7106521602475165646
+
+Let's look at some other methods:
+
+    >>> storage.getName()
+    "DemoStorage('base.fs', 'changes.fs')"
+
+    >>> storage.sortKey() == changes.sortKey()
+    True
+
+    >>> storage.getSize() == changes.getSize()
+    True
+    
+    >>> len(storage) == len(changes)
+    True
+
+    
+Undo methods are simply copied from the changes storage:
+
+    >>> [getattr(storage, name) == getattr(changes, name)
+    ...  for name in ('supportsUndo', 'undo', 'undoLog', 'undoInfo')
+    ...  ]
+    [True, True, True, True]

src/ZODB/component.xml

@@ -174,9 +174,9 @@
 
   <sectiontype name="demostorage" datatype=".DemoStorage"
                implements="ZODB.storage">
-    <key name="name" default="Demo Storage"/>
-    <section type="ZODB.storage" name="*" attribute="base"/>
-    <key name="quota" datatype="integer"/>
+    <key name="name" />
+    <section type="ZODB.storage" name="*" attribute="base" />
+    <section type="ZODB.storage" name="changes" attribute="changes" />
   </sectiontype>
 
 

src/ZODB/config.py

@@ -125,9 +125,11 @@ class DemoStorage(BaseConfig):
             base = self.config.base.open()
         else:
             base = None
-        return DemoStorage(self.config.name,
-                           base=base,
-                           quota=self.config.quota)
+        if self.config.changes:
+            changes = self.config.changes.open()
+        else:
+            changes = None
+        return DemoStorage(self.config.name, base=base, changes=changes)
 
 class FileStorage(BaseConfig):
 

src/ZODB/tests/testDemoStorage.py

@@ -12,16 +12,34 @@
 #
 ##############################################################################
 import unittest
-
+import random
 import transaction
 from ZODB.DB import DB
+from zope.testing import doctest
+import zope.testing.setupstack
 import ZODB.utils
 import ZODB.DemoStorage
-from ZODB.tests import StorageTestBase, BasicStorage
-from ZODB.tests import Synchronization
-
-class DemoStorageTests(StorageTestBase.StorageTestBase,
+from ZODB.tests import (
+    BasicStorage,
+    HistoryStorage,
+    IteratorStorage,
+    MTStorage,
+    PackableStorage,
+    RevisionStorage,
+    StorageTestBase,
+    Synchronization,
+    )
+
+class DemoStorageTests(
+    StorageTestBase.StorageTestBase,
     BasicStorage.BasicStorage,
+        
+    HistoryStorage.HistoryStorage,
+    IteratorStorage.ExtendedIteratorStorage,
+    IteratorStorage.IteratorStorage,
+    MTStorage.MTStorage,
+    PackableStorage.PackableStorage,
+    RevisionStorage.RevisionStorage,
     Synchronization.SynchronizedStorage,
     ):
 
@@ -44,6 +62,25 @@ class DemoStorageTests(StorageTestBase.StorageTestBase,
         self.assertEqual(s2.load(ZODB.utils.z64, ''),
                          self._storage.load(ZODB.utils.z64, ''))
 
+    def checkLengthAndBool(self):
+        self.assertEqual(len(self._storage), 0)
+        self.assert_(not self._storage)
+        db = DB(self._storage) # creates object 0. :)
+        self.assertEqual(len(self._storage), 1)
+        self.assert_(self._storage)
+        conn = db.open()
+        for i in range(10):
+            conn.root()[i] = conn.root().__class__()
+        transaction.commit()
+        self.assertEqual(len(self._storage), 11)
+        self.assert_(self._storage)
+        
+    def checkLoadBeforeUndo(self):
+        pass # we don't support undo yet
+    checkUndoZombie = checkLoadBeforeUndo
+
+    def checkPackWithMultiDatabaseReferences(self):
+        pass # we never do gc
         
 class DemoStorageWrappedBase(DemoStorageTests):
 
@@ -59,29 +96,92 @@ class DemoStorageWrappedBase(DemoStorageTests):
     def _makeBaseStorage(self):
         raise NotImplementedError
 
-class DemoStorageWrappedAroundFileStorage(DemoStorageWrappedBase):
+class DemoStorageWrappedAroundMappingStorage(DemoStorageWrappedBase):
 
     def _makeBaseStorage(self):
         from ZODB.MappingStorage import MappingStorage
         return MappingStorage()
 
-class DemoStorageWrappedAroundMappingStorage(DemoStorageWrappedBase):
+class DemoStorageWrappedAroundFileStorage(DemoStorageWrappedBase):
 
     def _makeBaseStorage(self):
         from ZODB.FileStorage import FileStorage
         return FileStorage('FileStorageTests.fs')
                        
 
+
+def setUp(test):
+    random.seed(0)
+    zope.testing.setupstack.setUpDirectory(test)
+    zope.testing.setupstack.register(test, transaction.abort)
+
+def testSomeDelegation():
+    r"""
+    >>> class S:
+    ...     def __init__(self, name):
+    ...         self.name = name
+    ...     def registerDB(self, db):
+    ...         print self.name, db
+    ...     def close(self):
+    ...         print self.name, 'closed'
+    ...     sortKey = getSize = __len__ = history = getTid = None
+    ...     tpc_finish = tpc_vote = tpc_transaction = None
+    ...     _lock_acquire = _lock_release = lambda: None
+    ...     getName = lambda self: 'S'
+    ...     isReadOnly = tpc_transaction = None
+    ...     supportsUndo = undo = undoLog = undoInfo = None
+    ...     supportsTransactionalUndo = None
+    ...     def new_oid(self):
+    ...         return '\0' * 8
+    ...     def tpc_begin(self, t, tid, status):
+    ...         print 'begin', tid, status
+    ...     def tpc_abort(self, t):
+    ...         pass
+
+    >>> from ZODB.DemoStorage import DemoStorage
+    >>> storage = DemoStorage(base=S(1), changes=S(2))
+
+    >>> storage.registerDB(1)
+    2 1
+
+    >>> storage.close()
+    1 closed
+    2 closed
+
+    >>> storage.tpc_begin(1, 2, 3)
+    begin 2 3
+    >>> storage.tpc_abort(1)
+
+    """
+
+def test_suite():
+    return unittest.TestSuite((
+        doctest.DocFileSuite('synchronized.txt'),
+        doctest.DocTestSuite(
+            setUp=setUp, tearDown=zope.testing.setupstack.tearDown,
+            ),
+        doctest.DocFileSuite(
+            'README.txt',
+            setUp=setUp, tearDown=zope.testing.setupstack.tearDown,
+            ),
+        ))
+
+
+
+
 def test_suite():
-    suite = unittest.TestSuite()
+    suite = unittest.TestSuite((
+        doctest.DocTestSuite(
+            setUp=setUp, tearDown=zope.testing.setupstack.tearDown,
+            ),
+        doctest.DocFileSuite(
+            '../DemoStorage.test',
+            setUp=setUp, tearDown=zope.testing.setupstack.tearDown,
+            ),
+        ))
     suite.addTest(unittest.makeSuite(DemoStorageTests, 'check'))
     suite.addTest(unittest.makeSuite(DemoStorageWrappedAroundFileStorage,
                                      'check'))
     suite.addTest(unittest.makeSuite(DemoStorageWrappedAroundMappingStorage,
                                      'check'))
     return suite
-
-if __name__ == "__main__":
-    loader = unittest.TestLoader()
-    loader.testMethodPrefix = "check"
-    unittest.main(testLoader=loader)