docker-offlineimap/offlineimap/folder/LocalStatusSQLite.py
Nicolas Sebrecht 3f70d9ef37 sqlite: open database when we use it rather than at instantiation time
Backported from 8e995a69bfa003ab822b55731429d84b3bc5626f.

We currently close the database as soon as possible while we handle the status
backend but this is still too early because autorefresh induces looping on this
code block.

Instead of delaying the closing outside of the loop, it's easier to delay the
opening as late as possible (inside the loop). The downside is that the database
is opened/closed more than once when autorefresh is enabled. The good news is
that this make the code much easier.

Fixes regression introduces by 6fb5700.

Reported-by: Łukasz Żarnowiecki <dolohow@outlook.com>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>
2016-06-08 01:59:39 +02:00

417 lines
16 KiB
Python

# 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
from sys import exc_info
from threading import Lock
try:
import sqlite3 as sqlite
except:
pass #fail only if needed later on, not on import
from .Base import BaseFolder
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
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.messagelist = {}
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)
# This lock protects against concurrent writes in same connection.
self._dblock = Lock()
self.connection = None
def openfiles(self):
# 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 cannot connect "
"with available bindings to '%s'. Is the sqlite3 package "
"installed?."% self.filename), None, exc_info()[2]
except sqlite.OperationalError as e:
# Operation had failed.
raise 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)), None, exc_info()[2]
# 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.__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 storesmessages(self):
return False
def getfullname(self):
return self.filename
# Interface from LocalStatusFolder
def isnewfolder(self):
return self._newfolder
# Interface from LocalStatusFolder
def deletemessagelist(self):
"""Delete all messages in the db."""
self.__sql_write('DELETE FROM status')
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)
# 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.messagelist = {}
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):
try:
self.connection.close()
except:
pass
def dropmessagelistcache(self):
self.messagelist = {}
# Interface from LocalStatusFolder
def save(self):
pass
# Noop. every transaction commits to database!
def saveall(self):
"""Saves the entire messagelist to the database."""
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 getmessagelist(self):
return self.messagelist
# 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))
self.__sql_write('INSERT INTO status (id,flags,mtime,labels) VALUES (?,?,?,?)',
(uid,flags,mtime,labels))
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=?', zip(uidlist, ), True)
for uid in uidlist:
del(self.messagelist[uid])