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