def _update_page(self, page, cache): ''' Write in the temp_cache given by _read_page ''' page_content = JSONStorage(find_nth_file(self.name, os.getcwd()+'/'+self._db.db_name, page)) page_content.write(cache)
def __init__(self, name, database):
# The maximum limit of each JSON file
self.FILE_SIZE_LIMIT = 100
# The write-in frequency
self.WRITE_IN_FREQ = 0.1
# The size for the query cache file
self.QUERY_CACHE_SIZE_LIMIT = 30
# The number of JSON files and the path for the current JSON file
self.file_num, self.current_file = find_current_file(name, os.getcwd()+'/'+database.db_name)
self.storage = JSONStorage(self.current_file)
self.name = name
self._db = database
# Cache for the whole collection
self._cache = {}
# Cache for the latest file that is being used to write in
self._current_cache = {}
#Cache for the most frequently queried items
# self._query_cache = LRUCache(self.QUERY_CACHE_SIZE_LIMIT)
# Each entry has a unique id as the primary key
existing_ids = self._read().keys()
if existing_ids:
self._last_id = max(i for i in existing_ids)
else:
self._last_id = 0
self._load_query_cache()
self.update_storage()
def update_storage(self):
if len(self._current_cache) >= self.FILE_SIZE_LIMIT:
# If we enter this function because of the file size limit, we do the following:
## write to the file
## create the next file
## point our current storage block to the next file
self.storage.write(dict(self._current_cache))
# print time.ctime(), 'size limit'
self._current_cache = {}
self.file_num += 1
self.storage = JSONStorage(os.getcwd()+'/'+ self._db.db_name + '/' + self.name + '_' + str(self.file_num) + '.json')
else:
# Else, it is just because of the timer expiration, we do the regular write-in
# print time.ctime(), 'regular write-in', len(self._current_cache)
self.storage.write(dict(self._current_cache))
self.query_storage.write(self._query_cache.items)
# print self._query_cache.items
# Set the timer again. Make it periodic.
self.t = threading.Timer(self.WRITE_IN_FREQ, self.update_storage)
self.t.start()
def _load_query_cache(self): self.query_storage = JSONStorage(os.getcwd()+'/'+ self._db.db_name + '/' + self.name + '_query.json') self._query_cache = LRUCache(self.QUERY_CACHE_SIZE_LIMIT, self.query_storage.read(is_ordered_dict=True))
class Collection(object):
def __init__(self, name, database):
# The maximum limit of each JSON file
self.FILE_SIZE_LIMIT = 100
# The write-in frequency
self.WRITE_IN_FREQ = 0.1
# The size for the query cache file
self.QUERY_CACHE_SIZE_LIMIT = 30
# The number of JSON files and the path for the current JSON file
self.file_num, self.current_file = find_current_file(name, os.getcwd()+'/'+database.db_name)
self.storage = JSONStorage(self.current_file)
self.name = name
self._db = database
# Cache for the whole collection
self._cache = {}
# Cache for the latest file that is being used to write in
self._current_cache = {}
#Cache for the most frequently queried items
# self._query_cache = LRUCache(self.QUERY_CACHE_SIZE_LIMIT)
# Each entry has a unique id as the primary key
existing_ids = self._read().keys()
if existing_ids:
self._last_id = max(i for i in existing_ids)
else:
self._last_id = 0
self._load_query_cache()
self.update_storage()
def setting(self, file_size=None, query_cache_size=None, write_freq=None):
if file_size is not None:
self.FILE_SIZE_LIMIT = file_size
if query_cache_size is not None:
self.QUERY_CACHE_SIZE_LIMIT = query_cache_size
if write_freq is not None:
self.WRITE_IN_FREQ = write_freq
def _load_query_cache(self):
self.query_storage = JSONStorage(os.getcwd()+'/'+ self._db.db_name + '/' + self.name + '_query.json')
self._query_cache = LRUCache(self.QUERY_CACHE_SIZE_LIMIT, self.query_storage.read(is_ordered_dict=True))
# print self._query_cache.items.keys()
def update_storage(self):
if len(self._current_cache) >= self.FILE_SIZE_LIMIT:
# If we enter this function because of the file size limit, we do the following:
## write to the file
## create the next file
## point our current storage block to the next file
self.storage.write(dict(self._current_cache))
# print time.ctime(), 'size limit'
self._current_cache = {}
self.file_num += 1
self.storage = JSONStorage(os.getcwd()+'/'+ self._db.db_name + '/' + self.name + '_' + str(self.file_num) + '.json')
else:
# Else, it is just because of the timer expiration, we do the regular write-in
# print time.ctime(), 'regular write-in', len(self._current_cache)
self.storage.write(dict(self._current_cache))
self.query_storage.write(self._query_cache.items)
# print self._query_cache.items
# Set the timer again. Make it periodic.
self.t = threading.Timer(self.WRITE_IN_FREQ, self.update_storage)
self.t.start()
def process_element(self, func, cond=None, eid=None):
data = self._read()
if eid is not None:
for i in eid:
func(data, eid)
else:
for eid in list(data):
if cond(data[eid]):
func(data, eid)
self._write(data)
def _get_next_id(self):
current = self._last_id + 1
self._last_id = current
return current
def _read(self):
if self._cache == {}:
# When the current collection is first read, read it all at once to the cache.
self._read_all()
return self._cache
def _read_all(self):
for i in range(1, self.file_num+1):
raw = JSONStorage(find_nth_file(self.name, os.getcwd()+'/'+self._db.db_name, i)).read()
for key in list(raw):
eid = int(key)
self._cache[eid] = Element(raw[key], eid)
if i == self.file_num:
self._current_cache[eid] = Element(raw[key], eid)
def _write(self, values):
self.storage.write(values)
def __len__(self):
return len(self._read())
def all(self):
return list(self._read().values())
def insert(self, value):
eid = self._get_next_id()
self._cache[eid] = value
self._current_cache[eid] = value
'''
If the file in-use reaches the size limit, we do the following:
1. cancel the timer
2. enter the update_storage
Otherwise, we can just wait until the timer expires
'''
if len(self._current_cache) >= self.FILE_SIZE_LIMIT:
self.t.cancel()
self.update_storage()
def insert_multiple(self, values):
for value in values:
self.insert(value)
def update(self, fields, cond=None, eids= None):
'''
Update can be performed by specifying eid or cond, or both.
But at least one of them should be specified.
'''
if cond is None and eids is None:
eids = self._cache.keys()
if cond is not None:
eids = self._select_to_be_updated_eid(cond, eids)
pages_eid = self._group_eids(eids)
self._update_cache(eids, pages_eid, fields)
self._update_disk(pages_eid, fields)
def _update_disk(self, pages_eid, fields, remove=False):
# do the update for the files
temp_caches = {}
for page in pages_eid:
temp_caches[page] = self._read_page(page)
temp_caches[page] = self._write_in_page(fields, pages_eid[page], temp_caches[page], remove)
for page in temp_caches:
self._update_page(page, temp_caches[page])
def _group_eids(self, eids):
'''
group eids based on which page it belongs to
'''
pages_eid = {}
for i in eids:
page = int(math.ceil(float(i)/float(self.FILE_SIZE_LIMIT)))
if page not in pages_eid:
pages_eid[page] = [i]
else:
pages_eid[page].append(i)
return pages_eid
def _select_to_be_updated_eid(self, cond, eids):
# Given a condition, return a list of id that satisfies the condition
filtered_ids = []
if eids is None:
# if edis not specified, iterate all possible eids
for id in self._cache:
if cond(self._cache[id]):
filtered_ids.append(id)
else:
# check whether the given id satisfied the cond
for id in eids:
if cond(self._cache[id]):
filtered_ids.append(id)
return filtered_ids
def _update_cache(self, eids, pages_eid, fields=None, remove=False):
# update the cache first before write-in to the file
for i in eids:
if remove:
self._cache.pop(i, None)
else:
self._cache[i].update(fields)
for page in pages_eid:
if page == self.file_num:
for id in pages_eid[page]:
if remove:
self._current_cache.pop(id, None)
else:
self._current_cache[id].update(fields)
def _read_page(self, page):
'''
Used for update()
read every related page
return a temp_cache
'''
page_content = JSONStorage(find_nth_file(self.name, os.getcwd()+'/'+self._db.db_name, page)).read()
temp_cache = {}
for key in list(page_content):
id = int(key)
temp_cache[id] = Element(page_content[key], id)
return temp_cache
def _write_in_page(self, fields, eids, temp_cache, remove=False):
# write in the updated items
for eid in eids:
if remove:
temp_cache.pop(eid, None)
else:
try:
temp_cache[eid].update(fields)
except KeyError:
pass
return temp_cache
def _update_page(self, page, cache):
'''
Write in the temp_cache given by _read_page
'''
page_content = JSONStorage(find_nth_file(self.name, os.getcwd()+'/'+self._db.db_name, page))
page_content.write(cache)
def remove(self, cond=None, eids=None):
if cond is None and eids is None:
# this means removing all elements
eids = self._cache.keys()
if cond is not None:
eids = self._select_to_be_updated_eid(cond, eids)
pages_eid = self._group_eids(eids)
self._update_cache(eids, pages_eid, fields=None, remove=True)
self._update_disk(pages_eid, fields=None, remove=True)
def search(self, cond, keys=None):
elements = self._query_cache.get(str(cond))
if elements == -1:
elements = [e for e in self.all() if cond(e)]
self._query_cache.set(str(cond), elements)
if keys is not None:
selected_elements = [{key: e[key] for key in keys} for e in elements]
return selected_elements
return elements
def clear(self):
self.remove()
def get(self, cond=None, eid=None):
if eid is not None:
read_all = self._read()
return read_all[eid]
elements = self.search(cond)
if elements == []:
return {}
return elements[0]
def close(self):
# when closing the database, remember to store those that are still in cache and cancel the write-in.
self.t.cancel()
self.update_storage()
self._cache.clear()
self._current_cache.clear()
self.t.cancel()
