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//usr/lib64/python2.7/site-packages/mx/BeeBase/BeeDict.py
""" BeeDict - On-disk dictionary like databases """ import exceptions, os import BeeIndex,BeeStorage from mx import Tools freeze = Tools.freeze from mx.Log import * #import TraceCalls; TraceCalls.install() #log.setup(ignore_level=SYSTEM_LOG_EVERYTHING) ### Globals # Write debug info _debug = 0 ### Constants # Special keys FirstKey = BeeIndex.FirstKey LastKey = BeeIndex.LastKey # Maximal cache size default value ( == size of transaction log; kept in memory !) MAXCACHESIZE = 1000 ### Errors class Error(exceptions.StandardError): pass class IndexError(Error): """ This error is raised for index related errors. """ pass class RecreateIndexError(IndexError): """ This error is raised in case the index for a dictionary was not found and/or needs to be recreated by running recovery. """ pass class RecoverError(Error): """ This error is raised in case the storage for a dictionary was found to be in an inconsistent state. """ pass ### Base classes # State constants READ = 0 MODIFIED = 1 DELETED = 2 READKEYONLY = 3 # XXX Currently not used. class BeeBaseDict: """ Base class that collects some method that all dicts can usually share without modification. The base class implements a transaction based caching mechanism. The cache stores data in the form key:(state,value) where state is: * READ for read but not yet modified * MODIFIED for added/modified * DELETED for deleted * READKEYONLY for key read, value still on disk The .commit method has to implement the needed disk mechanism to write the cache data to disk storage. """ # Name of the dictionary name = 'NoName' # Name of the storage file; set in .__init__() storage_name = name + '.dat' # Name of the index file; set in .__init__() index_name = name + '.idx' # Bee*Index object index = None # Bee*Storage object storage = None # Is the dictionary closed ? closed = 0 # Cache dictionary cache = None # Is the dictionary read-only ? readonly = 0 # Run in auto-commit mode ? This will perform a commit whenever # the cache gets to full. autocommit = 0 # Max. cache size in number of items to store in the in-memory # transaction cache maxcachesize = MAXCACHESIZE # Special keys that can be used for .cursor() FirstKey = FirstKey LastKey = LastKey def __init__(self, name, keysize=8, min_recordsize=0, readonly=0, recover=0, autocommit=0, validate=0, index=BeeIndex.BeeIntegerIndex, maxcachesize=None): """ Create an instance using name as basename for the data and index files. Two files will be created: <name>.dat and <name>.idx. keysize gives the maximal size of the key strings used as index keys. This is only useful for string based keys. min_recordsize is passed to the BeeStorage as indicator of the minimum size for data records. readonly can be set to true to open the files in read-only mode, preventing any disk modifications. To open the dictionary in recovery mode, pass a keyword recover=1. Then run .recover() and reopen using the normal settings. If autocommit is true the cache control will do an automatic .commit() whenever the transaction log overflows. If validate is true, the dictionary will run a validation check after having successfully opened storage and index. RecreateIndexError or RecoverError exceptions could be raised in case inconsistencies are found. index gives the constructor to use for the .index. The constructors BeeIntegerIndex and BeeStringIndex from the BeeIndex module are supported. maxcachesize defines the maximum size of the in-memory transaction cache. It defaults to MAXCACHESIZE if not given. """ # Init instance vars self.name = name self.storage_name = name + '.dat' self.index_name = name + '.idx' self.cache = {} if maxcachesize is not None: self.maxcachesize = maxcachesize else: self.maxcachesize = self.maxcachesize # Open storage self.storage = BeeStorage.BeeKeyValueStorage( self.storage_name, lock= not readonly, cache=0, min_recordsize=min_recordsize, readonly=readonly, recover=recover) # Determine the filemode for the index if readonly: # Readonly mode filemode = 1 else: if self.storage.is_new or recover: # Create a new file (overwriting a possibly existing one) filemode = 2 else: # Open an existing file, recreate if non-existing filemode = 0 # Open the index try: # Special argument treatment for the indexes; we check # depending on the used constructor function if (index is BeeIndex.BeeStringIndex or index is BeeIndex.BeeFixedLengthStringIndex): # Calculate the right sectorsize if keysize <= 30: sectorsize = 256 elif keysize <= 73: sectorsize = 512 elif keysize <= 158: sectorsize = 1024 else: raise IndexError, 'keysize %i is too large' % keysize self.index = index(self.index_name, keysize, dupkeys=0, filemode=filemode, sectorsize=sectorsize) elif index is BeeIndex.BeeIntegerIndex: # keysize is sizeof(long) self.index = index(self.index_name, dupkeys=1, filemode=filemode, sectorsize=256) elif index is BeeIndex.BeeFloatIndex: # keysize is sizeof(double) self.index = index(self.index_name, dupkeys=1, filemode=filemode, sectorsize=256) else: raise IndexError, 'unknown index type: %s' % repr(index) except IOError, why: # Make sure the storage lock is freed self.close() raise RecreateIndexError,\ 'Index for %s "%s" could not be opened' % \ (index.__name__, name) self.readonly = readonly self.autocommit = autocommit if validate: self.validate_index() self.validate_storage() def _calc_sectorsize(self, keysize): """ Calculate the sectorsize given the keysize. """ if keysize <= 30: return 256 elif keysize <= 73: return 512 elif keysize <= 158: return 1024 else: raise IndexError, 'keysize %i is too large' % keysize def remove_files(self): """ Deletes the storage and index files used for the instance. Closes the on-disk dictionary before proceeding with the removal. USE WITH CARE ! """ self.close() os.remove(self.storage_name) os.remove(self.index_name) def __len__(self): """ This only gives correct results if no modifications are pending. """ # Check for uncommitted changes if self.cache and self.changed(): raise Error, 'uncommitted data exists; can\'t calculate length' return len(self.index) def close(self): """ Flush buffers and close. This issues a .rollback(), so the current transaction is rolled back. It also frees the lock on the used index. """ if not self.closed: self.rollback() for obj in (self.index, self.storage): if obj is not None: # .rollback will have flushed the buffers obj.close() self.closed = 1 def __del__(self, AttributeError=AttributeError): """ Make sure the object is closed and locks are freed. """ #print '__del__ %s' % repr(self) if not self.closed: try: self.close() except AttributeError: # Could occur during interpreter cleanup pass def flush(self): """ Flush buffers to disk. """ if self.closed: # Nothing much to do return if self.storage is not None: self.storage.flush() if self.index is not None: self.index.flush() def __repr__(self): return '<%s instance for "%s" at 0x%x>' % (self.__class__.__name__, self.name, id(self)) def commit(self): """ Commit all changes and start a new transaction. This method does not implement any write operation, but takes care of managing the cache and flushing the storage and index buffers. You must override this method to have commit have any writing effect. The base method must be called after the cache has been processed. """ # Clear cache if self.cache is not None: self.cache.clear() # Flush storage and index self.flush() def rollback(self): """ Take back all changes and start a new transaction. Overriding is normally not needed. This method only takes care of managing the cache and flushing the storage and index buffers. """ # Clear cache if self.cache is not None: self.cache.clear() # Flush storage and index self.flush() def changed(self, modified=(MODIFIED,DELETED)): """ Return true in case the current transaction includes changes to the database, false otherwise. """ if self.cache: for key,(state,value) in self.cache.items(): if state in modified: return 1 return 0 def free_cache(self, len=len,unmodified=(READ,READKEYONLY)): """ Remove all unmodified entries from the cache. If self.autocommit and the cache cleanup did not reduce the size below the .maxcachesize limit, a .commit() will be executed automatically. Otherwise the processing continues. If the cache size hits 2 * .maxcachesize, a forced .rollback() is done and an error raised. """ cache = self.cache for key,(state,value) in cache.items(): if state in unmodified: del cache[key] size = len(cache) if size > self.maxcachesize: if self.autocommit: self.commit() return log(SYSTEM_ERROR, 'Cache overflow: %i modified items in cache',size) if size > 2 * self.maxcachesize: # Force .rollback() and raise an error log(SYSTEM_ERROR, 'Cache overflow: forced a .rollback()') self.rollback() raise Error,'cache overflow; last transaction rolled back' def read(self,key,checkonly=0): """ Read and return the value corresponding to key. If checkonly is true, only the availability of a value has to be checked. Override this method with an implementation that accesses the disk. """ raise KeyError,'key not found' def __setitem__(self,key,value, MODIFIED=MODIFIED): """ Save the item in the dictionary. Note that it is written to the cache first. Use .commit() to make sure it is written to disk. """ self.cache[key] = (MODIFIED, value) def __getitem__(self,key, validstates=(READ,MODIFIED),len=len,KeyError=KeyError, DELETED=DELETED,READ=READ): """ Get an item from the dictionary. This first tries to read the item from cache and reverts to the disk storage if it is not found. """ try: cache = self.cache state,value = cache[key] if state in validstates: return value except KeyError: pass else: if state == DELETED: raise KeyError,'key deleted' # Read from disk value = self.read(key) # Cache the item if len(cache) > self.maxcachesize: self.free_cache() cache[key] = (READ, value) return value def __delitem__(self, key, DELETED=DELETED): """ Delete an item. The item is only marked for deletion. The next .commit() will make the action permanent. """ cache = self.cache if not cache.has_key(key): self.read(key, 1) cache[key] = (DELETED, None) def has_key(self,key, len=len,KeyError=KeyError,DELETED=DELETED,READ=READ): """ Check if the dictionary has an item indexed by key. Successfully found items are put in the cache for fast subsequent access. """ try: cache = self.cache state,value = cache[key] if state == DELETED: return 0 return 1 except KeyError: pass # Read from disk try: value = self.read(key) except KeyError: return 0 # Cache the item if len(cache) > self.maxcachesize: self.free_cache() cache[key] = (READ, value) return 1 def get(self,key,default=None, len=len,KeyError=KeyError,DELETED=DELETED,READ=READ): """ Get item indexed by key from the dictionary or default if no such item exists. This first tries to read the item from cache and reverts to the disk storage if it is not found. """ try: cache = self.cache state,value = cache[key] if state == DELETED: return default return value except KeyError: pass # Read from disk try: value = self.read(key) except KeyError: return default # Cache the item if len(cache) > self.maxcachesize: self.free_cache() cache[key] = (READ, value) return value def cursor(self, key=FirstKey, default=None): """ Return a cursor instance for this kind of dictionary. If key is given, the cursor is positioned on that key in the dictionary. Otherwise, the first entry in the dictionary is used which guarantees that all entries are scanned. In case the key is not found, default is returned instead. Note that cursors operate with the data on disk meaning that any uncommitted changes will not be seen by the cursor. Has to be overridden to return a suitable cursor object. """ # Check for uncommitted changes if self.cache and self.changed(): raise Error,'uncommitted data exists' # Get the index cursor and create a dict cursor from it cursor = self.index.cursor(key,None) if cursor is None: return default return BeeBaseDictCursor(self,cursor) def garbage(self): """ Determine the amount of garbage in bytes that has accumulated in the storage file. This amount would be freed if .collect() were run. """ valid,old,invalid = self.storage.statistics() return old + invalid def collect(self): """ Run the storage garbage collector. Storage collection can only be done for writeable dictionaries and then only if the current transaction does not contain any pending changes. This can take a while depending on the size of the dictionary. """ if self.readonly: raise Error,'dict is read-only' # Check for uncommitted changes if self.cache and self.changed(): raise Error,'uncommitted data exists' self.flush() log(SYSTEM_INFO,'Collecting %s',self) # Run collector self.storage.collect(self.collect_callback) # End the storage transaction self.storage.end_transaction() def collect_callback(self,old_position,new_position,raw_data): """ Internal callback used to update the index when the storage garbage collector moves a record. This method must be overridden to account for the different indexing schemes. """ raise Error,'.collect_callback() not implemented' def recover(self): """ Recover all valid records and recreate the index. """ log(SYSTEM_INFO,'Recovering %s',self) # Clear the index self.index.clear() # Run recovery and recreate the index through the callback self.storage.recover(self.recover_callback) # End the storage transaction self.storage.end_transaction() def recover_callback(self,old_position,new_position,raw_data): """ Internal callback used to update the index when the storage recovery collector finds a record. old_position is only given as additional information, new_position contains the position of the found record. This method must be overridden to account for the different indexing schemes. """ raise Error,'.recover_callback() not implemented' def validate_index(self): """ Checks the consistency of the index and raises an RecreateIndexError in case the index is found to be inconsistent. Validation takes places for the data on disk. The in memory data is not checked. """ log(SYSTEM_INFO,'Validating index for %s',self) if not self.index.validate(): raise RecreateIndexError,'index is inconsistent' def validate_storage(self): """ Checks the consistency of the storage and raises an RecoverError in case it is found to be inconsistent. Validation takes places for the data on disk. The in memory data is not checked. XXX This currently does nothing since storages don't support validation yet. """ log(SYSTEM_INFO,'Validating storage for %s',self) return def backup(self,archive=None): """ Issues a backup request to the storage using archive which defaults to the storage filename + '.backup'. This causes an implicit .rollback() to be done. """ self.rollback() self.storage.backup(archive) def restore(self,archive): """ Restores the storage from an archive file. XXX Currently does NOT work. """ raise SystemError,'.restore() not implemented !' ### Iterator interface def __iter__(self, method='items'): """ Iterator interface. Creates an iterator which iterates over the items of the complete dictionary. Note that this only works if there are no uncommitted changes. """ cursor = self.cursor(FirstKey) if cursor is None: return EmptyIterator() if method == 'items': return BeeBaseIterator(cursor) elif method == 'keys': return BeeBaseIterator(cursor, cursor.read_key) elif method == 'values': return BeeBaseIterator(cursor, cursor.read_value) else: raise ValueError, 'unknown iterator method: %s' % method def iteritems(self): """ Returns an iterator to iterate over the items of the dictionary. """ return self.__iter__() def iterkeys(self): """ Returns an iterator to iterate over the keys of the dictionary. """ return self.__iter__('keys') def itervalues(self): """ Returns an iterator to iterate over the values of the dictionary. """ return self.__iter__('values') ### BeeBase iterators # To make iterators work in Python 2.1 and below try: StopIteration except NameError: class StopIteration(exceptions.IndexError): pass class EmptyIterator: """ Empty iterator. """ def next(self): raise StopIteration def __getitem__(self, index): raise StopIteration class BeeBaseIterator: """ Iterator for BeeBaseDict subclasses. """ def __init__(self, cursor, read_method=None): """ Iterate over cursor and return the values which the read_method function returns when called without arguments. If read_method is None, cursor.read_item is used. """ self.cursor = cursor if read_method is None: self.read_method = cursor.read_item else: self.read_method = read_method self.stop = 0 def next(self): if self.stop: raise StopIteration x = self.read_method() self.stop = not self.cursor.next() return x def __getitem__(self, index): return self.next() ### Cursor base class class BeeBaseDictCursor: """ Cursor for BeeBaseDict subclasses. The read/read_key/write methods assume that the dictionary uses a BeeKeyValueStorage instances as storage facility. Note that modifying the targetted dictionary while using a cursor can cause the cursor to skip new entries or fail due to deleted items. Especially deleting the key to which the cursor currently points can cause errors to be raised. In all other cases, the cursor will be repositioned. """ cursor = None def __init__(self,dict,cursor): self.dict = dict self.cursor = cursor self.key = cursor.key self.value = cursor.value # Alias self.read_value = self.read def position(self, key, value=None): """ Position the index cursor to index[key]. If value is given, index[key] == value is assured. key may also be FirstKey or LastKey (in which case value has to be None). """ # Create and position the cursor self.cursor = cursor = self.dict.index.cursor(key) if value and cursor.value != value: # assure that the cursor points to key,value while cursor.next(): if cursor.value == value: break if cursor.key != key: raise KeyError,'key not found' else: raise KeyError,'key not found' self.key = key self.value = value def next(self): """ Moves to the next entry in the dictionary. Returns true on success, false if the end-of-data has been reached. """ cursor = self.cursor if not cursor.valid: self.position(self.key,self.value) cursor = self.cursor rc = cursor.next() self.key = cursor.key self.value = cursor.value return rc def prev(self): """ Moves to the previous entry in the dictionary. Returns true on success, false if the end-of-data has been reached. """ cursor = self.cursor if not cursor.valid: self.position(self.key,self.value) cursor = self.cursor rc = cursor.prev() self.key = cursor.key self.value = cursor.value return rc def read(self): """ Reads the value object from the dict to which the cursor currently points. This method assumes a BeeKeyValueStorage instance in self.storage and an index that holds copies of the key objects. Override if this is not the case. """ return self.dict[self.key] def read_key(self): """ Reads the key object from the dict to which the cursor currently points. This method is intended for dictionaries that store hash values in the index. Normally, accessing the instance variable .key would give the current key object. This method assumes a BeeKeyValueStorage instance in self.storage. Override if this is not the case. """ return self.dict.storage.read_key(self.value) def read_item(self): """ Reads the (key, value) item object from the dict to which the cursor currently points. This method is intended for dictionaries that store hash values in the index. This method assumes a BeeKeyValueStorage instance in self.storage. Override if this is not the case. """ keyobj = self.dict.storage.read_key(self.value) return keyobj, self.dict[keyobj] def write(self,object): """ Writes the value object to the dict under the key to which the cursor currently points. The new data is not written to disk until the dictionaries current transaction is committed. This method assumes a BeeKeyValueStorage instance in self.storage and an index that holds copies of the key objects. Override if this is not the case. """ self.dict[self.key] = object ### Actual implementations class BeeDict(BeeBaseDict): """ On-disk dictionary that uses a "hash to address" index. Both Keys and values must be pickleable. Keys also have to be hashable. Both can have arbitrary size (keys shouldn't be too long though). Hash collisions are treated by sequential reads of all records with the same hash value and testing for equality of keys. This can be expensive ! """ # Count the number of hash collisions in writes collisions = 0 def __init__(self,name,min_recordsize=0,readonly=0,recover=0, autocommit=0,validate=0, maxcachesize=None, basemethod=BeeBaseDict.__init__): """ Create an instance using name as basename for the data and index files. Two files will be created: <name>.dat and <name>.idx. min_recordsize is passed to the BeeStorage as indicator of the minimum size for data records. readonly can be set to true to open the files in read-only mode, preventing any disk modifications. To open the dictionary in recovery mode, pass a keyword recover=1. Then run .recover() and reopen using the normal settings. If autocommit is true the cache control will do an automatic .commit() whenever the transaction log overflows. If validate is true, the dictionary will run a validation check after having successfully opened storage and index. RecreateIndexError or RecoverError exceptions could be raised in case inconsistencies are found. maxcachesize defines the maximum size of the in-memory transaction cache. It defaults to MAXCACHESIZE if not given. """ basemethod(self, name, min_recordsize=min_recordsize, readonly=readonly, recover=recover, autocommit=autocommit, validate=validate, index=BeeIndex.BeeIntegerIndex, maxcachesize=maxcachesize) def find_address(self,cursor,hashvalue,key): """ Find the address of a key by scanning the hash value set pointed to by the cursor. Returns the address of the found key or None. """ while cursor.next(): if cursor.key != hashvalue: # Left set of identical keys in index: not found return None if key == self.storage.read_key(cursor.value): # Found return cursor.value # EOF reached index: not found return None def index_cursor(self, key=FirstKey, default=None): """ Return an index cursor pointing to key. If key is not given, it defaults to FirstKey. In case the key is not found, default is returned. XXX Should use this method in more places... """ if key is FirstKey or key is LastKey: return self.index.cursor(key, default) hashvalue = hash(key) cursor = self.index.cursor(hashvalue,None) if cursor is None: return default # Check that we have really found the key address = cursor.value if key != self.storage.read_key(address): # Ah, a collision address = self.find_address(cursor,hashvalue,key) if address is None: return default return cursor def commit(self, basemethod=BeeBaseDict.commit,MODIFIED=MODIFIED,DELETED=DELETED): """ Commit all changes and start a new transaction. """ # Write all changed entries in the cache to disk index = self.index index_cursor = index.cursor index_update = index.update index_delete = index.delete storage = self.storage storage_read_key = storage.read_key storage_write = storage.write storage_delete = storage.delete readonly = self.readonly NotFound = None debug = _debug if debug: log(SYSTEM_DEBUG,'Committing all changes for "%s"...',self.name) for key,(state,value) in self.cache.items(): if state == MODIFIED: if debug: log.object(SYSTEM_DEBUG,' writing key %r:' % repr(key), value) if readonly: raise Error,'dict is read-only' hashvalue = hash(key) cursor = index_cursor(hashvalue, NotFound) if cursor is not NotFound: # Update an existing entry (or maybe add a new one if there # was a hash collision) address = cursor.value if key != storage_read_key(address): self.collisions = self.collisions + 1 address = self.find_address(cursor, hashvalue, key) # address may be None (== NotFound)... meaning # that we have to add a new record new_address = storage_write(key, value, address) if new_address == address: continue # Update index if address is not NotFound: index_update(hashvalue, new_address, address) else: index[hashvalue] = new_address else: # Add a new entry address = storage_write(key, value) # Update index index[hashvalue] = address elif state == DELETED: if debug: log(SYSTEM_DEBUG,' deleting key %r', repr(key)) if readonly: raise Error,'dict is read-only' hashvalue = hash(key) cursor = index_cursor(hashvalue) # Check that we have really found the key address = cursor.value if key != storage_read_key(address): # Ah, a collision address = self.find_address(cursor, hashvalue, key) if address is NotFound: raise KeyError,'key not found' storage_delete(address) # Update index index_delete(hashvalue, address) # End the storage transaction storage.end_transaction() # Call basemethod basemethod(self) def read(self,key,checkonly=0): # Load from disk hashvalue = hash(key) cursor = self.index.cursor(hashvalue) # Check that we have really found the key address = cursor.value if key != self.storage.read_key(address): # Ah, a collision address = self.find_address(cursor,hashvalue,key) if address is None: raise KeyError,'key not found' if checkonly: return else: return self.storage.read(address)[1] def keys(self, DELETED=DELETED): """ Return a list of keys. The method does not load any data into the cache, but does take notice of uncommitted changes. """ l = [] read_key = self.storage.read_key # First the cache entries that are not yet committed for key,(state,value) in self.cache.items(): if state != DELETED: l.append(key) # Next the remaining entries read from disk key_added = self.cache.has_key for address in self.index.values(): key = read_key(address) if not key_added(key): l.append(key) return l def values(self, DELETED=DELETED): """ Return a list of values. The method does not load any data into the cache, but does take notice of uncommitted changes. """ l = [] read = self.storage.read # First the cache entries that are not yet committed for key,(state,value) in self.cache.items(): if state != DELETED: l.append(value) # Next the remaining entries read from disk key_added = self.cache.has_key for address in self.index.values(): key,value = read(address) if not key_added(key): l.append(value) return l def items(self, DELETED=DELETED): """ Return a list of items. The method does not load any data into the cache, but does take notice of uncommitted changes. """ l = [] read = self.storage.read # First the cache entries that are not yet committed for key,(state,value) in self.cache.items(): if state != DELETED: l.append((key,value)) # Next the remaining entries read from disk key_added = self.cache.has_key for address in self.index.values(): key,value = read(address) if not key_added(key): l.append((key,value)) return l def cursor(self, key=FirstKey, default=None): """ Return a cursor instance for this kind of dictionary. If key is given, the cursor is positioned on that key in the dictionary. Otherwise, the first entry in the dictionary is used which guarantees that all entries are scanned. Note that cursors operate with the data on disk. The method will raise an error in case there are uncommitted changes pending. In case the key is not found, default is returned instead. """ # Check for uncommitted changes if self.cache and self.changed(): raise Error,'uncommitted data exists' # Get the index cursor and create a dict cursor from it cursor = self.index_cursor(key,None) if cursor is None: return default return BeeDictCursor(self,cursor) def collect_callback(self, old_position, new_position, raw_data): """ Internal callback used to update the index when the storage garbage collector moves a record. """ key = hash(self.storage.decode_key(raw_data)) try: self.index.update(key,new_position,old_position) except KeyError: # Ok, then we'll add the key as new entry log(SYSTEM_WARNING, 'Collect callback detected a missing key in ' 'index: %i; restoring it',old_position) self.index[key] = new_position def recover_callback(self, old_position, new_position, raw_data): """ Internal callback used to update the index when the storage recovery collector finds a record. old_position is only given as additional information. new_position contains the position of the found record. """ self.index[hash(self.storage.decode_key(raw_data))] = new_position ### class BeeDictCursor(BeeBaseDictCursor): """ Cursor for BeeDict instances. Since the keys are not kept directly in the index, .read_key() must be used to obtain the real key objects instead of querying the instance variable .key. """ def read(self): """ Reads the value object from the dict to which the cursor currently points. """ keyobj = self.dict.storage.read_key(self.value) return self.dict[keyobj] def read_key(self): """ Reads the key object from the dict to which the cursor currently points. """ return self.dict.storage.read_key(self.value) def read_item(self): """ Reads the (key, value) item object from the dict to which the cursor currently points. """ keyobj = self.dict.storage.read_key(self.value) return keyobj, self.dict[keyobj] def write(self,object): """ Writes the value object to the dict under the key to which the cursor currently points. The new data is not written to disk until the dictionary's current transaction is committed. """ keyobj = self.dict.storage.read_key(self.value) self.dict[keyobj] = object freeze(BeeDictCursor) ### class BeeStringDict(BeeBaseDict): """ A dictionary that is indexed by limited size strings. The key strings may *not* contain embedded \0 characters. Though the keys must be strings of limited size, the values can be any pickleable object. """ def __init__(self,name,keysize=10,min_recordsize=0,readonly=0,recover=0, autocommit=0,validate=0, maxcachesize=None, basemethod=BeeBaseDict.__init__): """ Create an instance using name as dictionary name. Two files will be created: <name>.dat and <name>.idx. keysize gives the maximal size of the strings used as index keys. min_recordsize gives a hint to the expected typical size of (key,value) pickles: all records will have at least this size. To open the dictionary in recovery mode, pass a keyword recover=1. Then run .recover() and reopen using the normal settings. If autocommit is true the cache control will do an automatic .commit() whenever the transaction log overflows. If validate is true, the dictionary will run a validation check after having successfully opened storage and index. RecreateIndexError or RecoverError exceptions could be raised in case inconsistencies are found. maxcachesize defines the maximum size of the in-memory transaction cache. It defaults to MAXCACHESIZE if not given. XXX Save keysize in storage file header. """ basemethod(self, name, keysize=keysize, min_recordsize=min_recordsize, readonly=readonly, recover=recover, autocommit=autocommit, validate=validate, index=BeeIndex.BeeStringIndex, maxcachesize=maxcachesize) def commit(self, basemethod=BeeBaseDict.commit,DELETED=DELETED,MODIFIED=MODIFIED): """ Commit all changes and start a new transaction. """ # Write all changed entries in the cache to disk index = self.index index_get = index.get storage = self.storage storage_write = storage.write storage_delete = storage.delete readonly = self.readonly NotFound = None debug = _debug if debug: log(SYSTEM_DEBUG,'Committing all changes for "%s"...',self.name) for key,(state,value) in self.cache.items(): if state == MODIFIED: if debug: log.object(SYSTEM_DEBUG,' writing key %s:' % repr(key), value) address = index_get(key,NotFound) if address is not NotFound: # Update storage new_addr = storage_write(key,value,address) if new_addr == address: continue # Update index index[key] = new_addr else: # Add to storage address = storage_write(key,value) # Add to the index index[key] = address elif state == DELETED: if debug: log(SYSTEM_DEBUG,' deleting key %s', repr(key)) if readonly: raise Error,'dict is read-only' address = index_get(key,NotFound) if address is not NotFound: # Delete record storage_delete(address) # Update Index del index[key] else: raise KeyError,'key not found' # End the storage transaction storage.end_transaction() # Call basemethod basemethod(self) def read(self,key,checkonly=0): address = self.index[key] if checkonly: return else: return self.storage.read(address)[1] def keys(self): """ Return a list of keys. The method will raise an error if there are uncommitted changes pending. Output is sorted ascending according to keys. """ if self.cache and self.changed(): raise Error,'uncommitted data exists' return self.index.keys() def values(self): """ Return a list of values. The method will raise an error if there are uncommitted changes pending. Output is sorted ascending according to keys. """ if self.cache and self.changed(): raise Error,'uncommitted data exists' l = [] read = self.storage.read for address in self.index.values(): l.append(read(address)[1]) return l def items(self): """ Return a list of items. The method will raise an error if there are uncommitted changes pending. Output is sorted ascending according to keys. """ if self.cache and self.changed(): raise Error,'uncommitted data exists' l = [] read = self.storage.read for address in self.index.values(): l.append(read(address)) return l def cursor(self, key=FirstKey, default=None): """ Return a cursor instance for this kind of dictionary. If key is given, the cursor is positioned on that key in the dictionary. Otherwise, the first entry in the dictionary is used which guarantees that all entries are scanned. Note that cursors operate with the data on disk meaning that any uncommitted changes will not be seen by the cursor. In case the key is not found, default is returned instead. """ # Check for uncommitted changes if self.cache and self.changed(): raise Error,'uncommitted data exists' # Get the index cursor and create a dict cursor from it cursor = self.index.cursor(key,None) if cursor is None: return default return BeeStringDictCursor(self,cursor) def collect_callback(self,old_position,new_position,raw_data): """ Internal callback used to update the index when the storage garbage collector moves a record. """ key = self.storage.decode_key(raw_data) try: self.index.update(key,new_position,old_position) except KeyError: # Ok, then we'll add the key as new entry log(SYSTEM_WARNING, 'Collect callback detected a missing key in ' 'index: %i; restoring it',old_position) self.index[key] = new_position def recover_callback(self,old_position,new_position,raw_data): """ Internal callback used to update the index when the storage recovery collector finds a record. old_position is only given as additional information. new_position contains the position of the found record. XXX What if the recovery collector find two records with the same key ? """ self.index[self.storage.decode_key(raw_data)] = new_position freeze(BeeStringDict) ### class BeeFixedLengthStringDict(BeeStringDict): """ A dictionary that is indexed by fixed length strings. The key strings may contain embedded \0 characters. Though the keys must be strings of limited size, the values can be any pickleable object. """ def __init__(self,name,keysize=10,min_recordsize=0,readonly=0,recover=0, autocommit=0,validate=0, maxcachesize=None, basemethod=BeeBaseDict.__init__): """ Create an instance using name as dictionary name. Two files will be created: <name>.dat and <name>.idx. keysize gives the maximal size of the strings used as index keys. min_recordsize gives a hint to the expected typical size of (key,value) pickles: all records will have at least this size. To open the dictionary in recovery mode, pass a keyword recover=1. Then run .recover() and reopen using the normal settings. If autocommit is true the cache control will do an automatic .commit() whenever the transaction log overflows. If validate is true, the dictionary will run a validation check after having successfully opened storage and index. RecreateIndexError or RecoverError exceptions could be raised in case inconsistencies are found. maxcachesize defines the maximum size of the in-memory transaction cache. It defaults to MAXCACHESIZE if not given. XXX Save keysize in storage file header. """ basemethod(self, name, keysize=keysize, min_recordsize=min_recordsize, readonly=readonly, recover=recover, autocommit=autocommit, validate=validate, index=BeeIndex.BeeFixedLengthStringIndex, maxcachesize=maxcachesize) freeze(BeeFixedLengthStringDict) ### class BeeStringDictCursor(BeeBaseDictCursor): """ Cursor for BeeStringDict and BeeFixedLengthStringDict instances. """ def read_key(self): """ Reads the key object from the dict to which the cursor currently points. """ return self.key def read_item(self): """ Reads the (key, value) item object from the dict to which the cursor currently points. """ return self.key, self.dict[self.key] freeze(BeeStringDictCursor) ### def AutoRecover(Class,*args,**kws): """ Wrapper that runs recovery whenever needed. This can still fail, but at least many "normal" failures can be handled this way automatically. """ try: d = apply(Class,args,kws) return d except BeeStorage.RunRecoveryError: pass except RecreateIndexError: pass except RecoverError: pass # Open in recovery mode log(SYSTEM_ERROR, 'Database "%s" is corrupt; trying recovery...',args[0]) new_kws = kws.copy() new_kws['readonly'] = 0 new_kws['validate'] = 0 #new_kws['lock'] = 1 new_kws['recover'] = 1 d = apply(Class,args,new_kws) # Run recover & close d.recover() del d # Reopen in original mode d = apply(Class,args,kws) log(SYSTEM_WARNING, 'Successfully recovered the database "%s"',args[0]) return d ### if __name__ == '__main__': import sys print 'Testing BeeStringDict...' s = BeeStringDict('test-BeeStringDict') s['Marc'] = 'Sveta' s['Thorsten'] = 'Petra' s['Christian'] = 'Leesa' s.commit() print 'Testing BeeDict...' d = BeeDict('test-BeeDict') d['Marc'] = 'Sveta' d['Thorsten'] = 'Petra' d['Christian'] = 'Leesa' d.commit() d['Marc'] = 'Sveta' * 100 d.commit() del d,s print 'Testing iteration...' d = BeeDict('test-BeeDict') d['Marc'] = 'Sveta' d['Thorsten'] = 'Petra' d['Christian'] = 'Leesa' d.commit() i = 0 for k,v in d.iteritems(): print '%s: %s' % (k,v) i = i + 1 assert i == 3 if sys.version[:3] >= '2.2': i = 0 for k,v in d: print '%s: %s' % (k,v) i = i + 1 assert i == 3 del d print 'Works.'
