# Local status cache virtual folder: SQLite backend # Copyright (C) 2009-2011 Stewart Smith and contributors # # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program; if not, write to the Free Software # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA import os.path import re from threading import Lock from .LocalStatus import LocalStatusFolder try: import sqlite3 as sqlite except: pass #fail only if needed later on, not on import class LocalStatusSQLiteFolder(LocalStatusFolder): """LocalStatus backend implemented with an SQLite database As python-sqlite currently does not allow to access the same sqlite objects from various threads, we need to open get and close a db connection and cursor for all operations. This is a big disadvantage and we might want to investigate if we cannot hold an object open for a thread somehow.""" #though. According to sqlite docs, you need to commit() before #the connection is closed or your changes will be lost!""" #get db connection which autocommits #connection = sqlite.connect(self.filename, isolation_level=None) #cursor = connection.cursor() #return connection, cursor #current version of our db format cur_version = 1 def __init__(self, name, repository): super(LocalStatusSQLiteFolder, self).__init__(name, repository) # dblock protects against concurrent writes in same connection self._dblock = Lock() #Try to establish connection, no need for threadsafety in __init__ try: self.connection = sqlite.connect(self.filename, check_same_thread = False) except NameError: # sqlite import had failed raise UserWarning('SQLite backend chosen, but no sqlite python ' 'bindings available. Please install.') #Make sure sqlite is in multithreading SERIALIZE mode assert sqlite.threadsafety == 1, 'Your sqlite is not multithreading safe.' #Test if db version is current enough and if db is readable. try: cursor = self.connection.execute("SELECT value from metadata WHERE key='db_version'") except sqlite.DatabaseError: #db file missing or corrupt, recreate it. self.upgrade_db(0) else: # fetch db version and upgrade if needed version = int(cursor.fetchone()[0]) if version < LocalStatusSQLiteFolder.cur_version: self.upgrade_db(version) def sql_write(self, sql, vars=None, executemany=False): """Execute some SQL, retrying if the db was locked. :param sql: the SQL string passed to execute() :param vars: the variable values to `sql`. E.g. (1,2) or {uid:1, flags:'T'}. See sqlite docs for possibilities. :param executemany: bool indicating whether we want to perform conn.executemany() or conn.execute(). :returns: the Cursor() or raises an Exception""" success = False while not success: self._dblock.acquire() try: if vars is None: if executemany: cursor = self.connection.executemany(sql) else: cursor = self.connection.execute(sql) else: if executemany: cursor = self.connection.executemany(sql, vars) else: cursor = self.connection.execute(sql, vars) success = True self.connection.commit() except sqlite.OperationalError as e: if e.args[0] == 'cannot commit - no transaction is active': pass elif e.args[0] == 'database is locked': self.ui.debug('', "Locked sqlite database, retrying.") success = False else: raise finally: self._dblock.release() return cursor def upgrade_db(self, from_ver): """Upgrade the sqlite format from version 'from_ver' to current""" if hasattr(self, 'connection'): self.connection.close() #close old connections first self.connection = sqlite.connect(self.filename, check_same_thread = False) if from_ver == 0: # from_ver==0: no db existent: plain text migration? self.create_db() # below was derived from repository.getfolderfilename() logic plaintextfilename = os.path.join( self.repository.account.getaccountmeta(), 'LocalStatus', self.getfolderbasename()) # MIGRATE from plaintext if needed if os.path.exists(plaintextfilename): self.ui._msg('Migrating LocalStatus cache from plain text ' 'to sqlite database for %s:%s' %\ (self.repository, self)) file = open(plaintextfilename, "rt") line = file.readline().strip() data = [] for line in file.xreadlines(): uid, flags = line.strip().split(':') uid = long(uid) flags = ''.join(sorted(flags)) data.append((uid,flags)) self.connection.executemany('INSERT INTO status (id,flags) VALUES (?,?)', data) self.connection.commit() file.close() os.rename(plaintextfilename, plaintextfilename + ".old") # Future version upgrades come here... # if from_ver <= 1: ... #upgrade from 1 to 2 # if from_ver <= 2: ... #upgrade from 2 to 3 def create_db(self): """Create a new db file""" self.ui._msg('Creating new Local Status db for %s:%s' \ % (self.repository, self)) if hasattr(self, 'connection'): self.connection.close() #close old connections first self.connection = sqlite.connect(self.filename, check_same_thread = False) self.connection.executescript(""" CREATE TABLE metadata (key VARCHAR(50) PRIMARY KEY, value VARCHAR(128)); INSERT INTO metadata VALUES('db_version', '1'); CREATE TABLE status (id INTEGER PRIMARY KEY, flags VARCHAR(50)); """) self.connection.commit() def isnewfolder(self): # testing the existence of the db file won't work. It is created # as soon as this class instance was intitiated. So say it is a # new folder when there are no messages at all recorded in it. return self.getmessagecount() > 0 def deletemessagelist(self): """delete all messages in the db""" self.sql_write('DELETE FROM status') def cachemessagelist(self): self.messagelist = {} cursor = self.connection.execute('SELECT id,flags from status') for row in cursor: flags = set(row[1]) self.messagelist[row[0]] = {'uid': row[0], 'flags': flags} def save(self): #Noop in this backend pass # Following some pure SQLite functions, where we chose to use # BaseFolder() methods instead. Doing those on the in-memory list is # quicker anyway. If our db becomes so big that we don't want to # maintain the in-memory list anymore, these might come in handy # in the future though. # #def uidexists(self,uid): # conn, cursor = self.get_cursor() # with conn: # cursor.execute('SELECT id FROM status WHERE id=:id',{'id': uid}) # return cursor.fetchone() # This would be the pure SQLite solution, use BaseFolder() method, # to avoid threading with sqlite... #def getmessageuidlist(self): # conn, cursor = self.get_cursor() # with conn: # cursor.execute('SELECT id from status') # r = [] # for row in cursor: # r.append(row[0]) # return r #def getmessagecount(self): # conn, cursor = self.get_cursor() # with conn: # cursor.execute('SELECT count(id) from status'); # return cursor.fetchone()[0] #def getmessageflags(self, uid): # conn, cursor = self.get_cursor() # with conn: # cursor.execute('SELECT flags FROM status WHERE id=:id', # {'id': uid}) # for row in cursor: # flags = [x for x in row[0]] # return flags # assert False,"getmessageflags() called on non-existing message" def savemessage(self, uid, content, flags, rtime): if uid < 0: # We cannot assign a uid. return uid if self.uidexists(uid): # already have it self.savemessageflags(uid, flags) return uid self.messagelist[uid] = {'uid': uid, 'flags': flags, 'time': rtime} flags = ''.join(sorted(flags)) self.sql_write('INSERT INTO status (id,flags) VALUES (?,?)', (uid,flags)) return uid def savemessageflags(self, uid, flags): self.messagelist[uid] = {'uid': uid, 'flags': flags} flags = ''.join(sorted(flags)) self.sql_write('UPDATE status SET flags=? WHERE id=?',(flags,uid)) def deletemessage(self, uid): if not uid in self.messagelist: return self.sql_write('DELETE FROM status WHERE id=?', (uid, )) del(self.messagelist[uid]) def deletemessages(self, uidlist): """Delete list of UIDs from status cache This function uses sqlites executemany() function which is much faster than iterating through deletemessage() when we have many messages to delete.""" # Weed out ones not in self.messagelist uidlist = [uid for uid in uidlist if uid in self.messagelist] if not len(uidlist): return # arg2 needs to be an iterable of 1-tuples [(1,),(2,),...] self.sql_write('DELETE FROM status WHERE id=?', zip(uidlist, ), True) for uid in uidlist: del(self.messagelist[uid])