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LocalStatusSQLite.py
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LocalStatusSQLite.py
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# Local status cache virtual folder: SQLite backend
# Copyright (C) 2009-2017 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
import sqlite3 as sqlite
from sys import exc_info
from threading import Lock
import six
from .Base import BaseFolder
class DatabaseFileLock(object):
"""Lock at database file level."""
def __init__(self):
self._lock = Lock()
self._counter = 0
def __enter__(self):
self._lock.acquire()
def __exit__(self, typ, value, tb):
self._lock.release()
def registerNewUser(self):
self._counter += 1
def removeOneUser(self):
self._counter -= 1
def getLock(self):
return self._lock
def shouldClose(self):
return self._counter < 1
class LocalStatusSQLiteFolder(BaseFolder):
"""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 = 2
# Keep track on how many threads need access to the database.
locks = {} # Key: filename, value: DatabaseFileLock instance.
def __init__(self, name, repository):
self.sep = '.' # Needs to be set before super().__init__().
super(LocalStatusSQLiteFolder, self).__init__(name, repository)
self.root = repository.root
self.filename = os.path.join(self.getroot(), self.getfolderbasename())
self._newfolder = False # Flag if the folder is new.
dirname = os.path.dirname(self.filename)
if not os.path.exists(dirname):
os.makedirs(dirname)
if not os.path.isdir(dirname):
raise UserWarning("SQLite database path '%s' is not a directory."%
dirname)
self.connection = None
# The lock serialize the writing/open/close of database accross threads.
if self.filename not in LocalStatusSQLiteFolder.locks:
LocalStatusSQLiteFolder.locks[self.filename] = DatabaseFileLock()
self._databaseFileLock = LocalStatusSQLiteFolder.locks[self.filename]
self._in_transactions = 0
def __enter__(self):
if not self.dofsync():
assert self.connection is not None
self._in_transactions += 1
def __exit__(self, exc_type, exc_val, exc_tb):
if not self.dofsync():
assert self._in_transactions > 0
self._in_transactions -= 1
if self._in_transactions < 1:
self.connection.commit()
def openfiles(self):
# Make sure sqlite is in multithreading SERIALIZE mode.
assert sqlite.threadsafety == 1, 'Your sqlite is not multithreading safe.'
with self._databaseFileLock.getLock():
# Try to establish connection, no need for threadsafety in __init__.
try:
self.connection = sqlite.connect(self.filename,
check_same_thread=False)
self._databaseFileLock.registerNewUser()
except sqlite.OperationalError as e:
# Operation had failed.
six.reraise(UserWarning,
UserWarning(
"cannot open database file '%s': %s.\nYou might"
" want to check the rights to that file and if "
"it cleanly opens with the 'sqlite<3>' command"%
(self.filename, e)),
exc_info()[2])
# 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.__create_db()
else:
# Fetch db version and upgrade if needed.
version = int(cursor.fetchone()[0])
if version < LocalStatusSQLiteFolder.cur_version:
self.__upgrade_db(version)
def purge(self):
"""Remove any pre-existing database. Do not call in dry-run mode."""
try:
os.unlink(self.filename)
except OSError as e:
self.ui.debug('', "could not remove file %s: %s"%
(self.filename, e))
def storesmessages(self):
return False
def getfullname(self):
return self.filename
# Interface from LocalStatusFolder
def isnewfolder(self):
return self._newfolder
def __sql_write(self, sql, args=None, executemany=False):
"""Execute some SQL, retrying if the db was locked.
:param sql: the SQL string passed to execute()
:param args: 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: None or raises an Exception."""
success = False
while not success:
try:
with self._databaseFileLock.getLock():
if args is None:
if executemany:
self.connection.executemany(sql)
else:
self.connection.execute(sql)
else:
if executemany:
self.connection.executemany(sql, args)
else:
self.connection.execute(sql, args)
success = True
if not self._in_transactions:
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
def __upgrade_db(self, from_ver):
"""Upgrade the sqlite format from version 'from_ver' to current"""
if self.connection is not None:
self.connection.close() # Close old connections first.
self.connection = sqlite.connect(self.filename,
check_same_thread=False)
# Upgrade from database version 1 to version 2
# This change adds labels and mtime columns, to be used by Gmail IMAP and Maildir folders.
if from_ver <= 1:
self.ui._msg('Upgrading LocalStatus cache from version 1 to version 2 for %s:%s'%
(self.repository, self))
self.connection.executescript("""ALTER TABLE status ADD mtime INTEGER DEFAULT 0;
ALTER TABLE status ADD labels VARCHAR(256) DEFAULT '';
UPDATE metadata SET value='2' WHERE key='db_version';
""")
self.connection.commit()
# Future version upgrades come here...
# if from_ver <= 2: ... #upgrade from 2 to 3
# if from_ver <= 3: ... #upgrade from 3 to 4
def __create_db(self):
"""Create a new db file.
self.connection must point to the opened and valid SQlite
database connection."""
self.ui._msg('Creating new Local Status db for %s:%s'%
(self.repository, self))
self.connection.executescript("""
CREATE TABLE metadata (key VARCHAR(50) PRIMARY KEY, value VARCHAR(128));
INSERT INTO metadata VALUES('db_version', '2');
CREATE TABLE status (id INTEGER PRIMARY KEY, flags VARCHAR(50), mtime INTEGER, labels VARCHAR(256));
""")
self.connection.commit()
self._newfolder = True
# Interface from BaseFolder
def msglist_item_initializer(self, uid):
return {'uid': uid, 'flags': set(), 'labels': set(), 'time': 0, 'mtime': 0}
# Interface from BaseFolder
def cachemessagelist(self):
self.dropmessagelistcache()
cursor = self.connection.execute('SELECT id,flags,mtime,labels from status')
for row in cursor:
uid = row[0]
self.messagelist[uid] = self.msglist_item_initializer(uid)
flags = set(row[1])
try:
labels = set([lb.strip() for lb in
row[3].split(',') if len(lb.strip()) > 0])
except AttributeError:
# FIXME: This except clause was introduced because row[3] from
# database can be found of unexpected type NoneType. See
# https://github.com/OfflineIMAP/offlineimap/issues/103
#
# We are fixing the type here but this would require more
# researches to find the true root cause. row[3] is expected to
# be a (empty) string, not None.
#
# Also, since database might return None, we have to fix the
# database, too.
labels = set()
self.messagelist[uid]['flags'] = flags
self.messagelist[uid]['labels'] = labels
self.messagelist[uid]['mtime'] = row[2]
def closefiles(self):
with self._databaseFileLock.getLock():
self._databaseFileLock.removeOneUser()
if self._databaseFileLock.shouldClose():
try:
self.connection.close()
except:
pass
# Interface from LocalStatusFolder
def save(self):
pass
# Noop. every transaction commits to database!
def saveall(self):
"""Saves the entire messagelist to the database."""
with self._databaseFileLock.getLock():
data = []
for uid, msg in self.messagelist.items():
mtime = msg['mtime']
flags = ''.join(sorted(msg['flags']))
labels = ', '.join(sorted(msg['labels']))
data.append((uid, flags, mtime, labels))
self.__sql_write('INSERT OR REPLACE INTO status '
'(id,flags,mtime,labels) VALUES (?,?,?,?)',
data, executemany=True)
# 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"
# Interface from BaseFolder
def savemessage(self, uid, content, flags, rtime, mtime=0, labels=set()):
"""Writes a new message, with the specified uid.
See folder/Base for detail. Note that savemessage() does not
check against dryrun settings, so you need to ensure that
savemessage is never called in a dryrun mode."""
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] = self.msglist_item_initializer(uid)
self.messagelist[uid] = {'uid': uid, 'flags': flags, 'time': rtime, 'mtime': mtime, 'labels': labels}
flags = ''.join(sorted(flags))
labels = ', '.join(sorted(labels))
try:
self.__sql_write('INSERT INTO status (id,flags,mtime,labels) VALUES (?,?,?,?)',
(uid,flags,mtime,labels))
except Exception as e:
six.reraise(UserWarning,
UserWarning("%s while inserting UID %s"%
(str(e), str(uid))),
exc_info()[2])
return uid
# Interface from BaseFolder
def savemessageflags(self, uid, flags):
assert self.uidexists(uid)
self.messagelist[uid]['flags'] = flags
flags = ''.join(sorted(flags))
self.__sql_write('UPDATE status SET flags=? WHERE id=?',(flags,uid))
def getmessageflags(self, uid):
return self.messagelist[uid]['flags']
def savemessagelabels(self, uid, labels, mtime=None):
self.messagelist[uid]['labels'] = labels
if mtime: self.messagelist[uid]['mtime'] = mtime
labels = ', '.join(sorted(labels))
if mtime:
self.__sql_write('UPDATE status SET labels=?, mtime=? WHERE id=?',(labels,mtime,uid))
else:
self.__sql_write('UPDATE status SET labels=? WHERE id=?',(labels,uid))
def savemessageslabelsbulk(self, labels):
"""
Saves labels from a dictionary in a single database operation.
"""
data = [(', '.join(sorted(l)), uid) for uid, l in labels.items()]
self.__sql_write('UPDATE status SET labels=? WHERE id=?', data, executemany=True)
for uid, l in labels.items():
self.messagelist[uid]['labels'] = l
def addmessageslabels(self, uids, labels):
data = []
for uid in uids:
newlabels = self.messagelist[uid]['labels'] | labels
data.append((', '.join(sorted(newlabels)), uid))
self.__sql_write('UPDATE status SET labels=? WHERE id=?', data, executemany=True)
for uid in uids:
self.messagelist[uid]['labels'] = self.messagelist[uid]['labels'] | labels
def deletemessageslabels(self, uids, labels):
data = []
for uid in uids:
newlabels = self.messagelist[uid]['labels'] - labels
data.append((', '.join(sorted(newlabels)), uid))
self.__sql_write('UPDATE status SET labels=? WHERE id=?', data, executemany=True)
for uid in uids:
self.messagelist[uid]['labels'] = self.messagelist[uid]['labels'] - labels
def getmessagelabels(self, uid):
return self.messagelist[uid]['labels']
def savemessagesmtimebulk(self, mtimes):
"""Saves mtimes from the mtimes dictionary in a single database operation."""
data = [(mt, uid) for uid, mt in mtimes.items()]
self.__sql_write('UPDATE status SET mtime=? WHERE id=?', data, executemany=True)
for uid, mt in mtimes.items():
self.messagelist[uid]['mtime'] = mt
def getmessagemtime(self, uid):
return self.messagelist[uid]['mtime']
# Interface from BaseFolder
def deletemessage(self, uid):
if not uid in self.messagelist:
return
self.__sql_write('DELETE FROM status WHERE id=?', (uid, ))
del(self.messagelist[uid])
# Interface from BaseFolder
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=?', list(zip(uidlist, )), True)
for uid in uidlist:
del(self.messagelist[uid])