[PATCH 5/7] Don't keep sqlite connections open
Sebastian Spaeth
Sebastian at SSpaeth.de
Thu May 5 13:59:27 UTC 2011
Due to non-threadsafeness, we need to close the sqlite connection after
we used it. It would be nicer to keep a cursor open, but apparently the
python bindings to sqlite don't allow this as early versions of sqlite
could not deal with several threads accessing an sqlite object.
Signed-off-by: Sebastian Spaeth <Sebastian at SSpaeth.de>
---
offlineimap/folder/LocalStatusSQLite.py | 199 ++++++++++++++++++++-----------
1 files changed, 127 insertions(+), 72 deletions(-)
diff --git a/offlineimap/folder/LocalStatusSQLite.py b/offlineimap/folder/LocalStatusSQLite.py
index c8c179f..dbfad54 100644
--- a/offlineimap/folder/LocalStatusSQLite.py
+++ b/offlineimap/folder/LocalStatusSQLite.py
@@ -23,7 +23,13 @@ except:
pass #fail only if needed later on, not on import
class LocalStatusSQLiteFolder(LocalStatusFolder):
- """LocalStatus backend implemented with an SQLite database"""
+ """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."""
#current version of the db format
cur_version = 1
@@ -32,9 +38,9 @@ class LocalStatusSQLiteFolder(LocalStatusFolder):
repository,
accountname,
config)
- #Try to establish connection
+ #Try to establish connection, no need for threadsafety in __init__
try:
- self.connection = sqlite.connect(self.filename)
+ connection = sqlite.connect(self.filename)
except NameError:
# sqlite import had failed
raise UserWarning('SQLite backend chosen, but no sqlite python '
@@ -43,19 +49,31 @@ class LocalStatusSQLiteFolder(LocalStatusFolder):
#Test if the db version is current enough and if the db is
#readable.
try:
- self.cursor = self.connection.cursor()
- self.cursor.execute("SELECT value from metadata WHERE key='db_version'")
+ cursor = connection.cursor()
+ cursor.execute("SELECT value from metadata WHERE key='db_version'")
except sqlite.DatabaseError:
#db file missing or corrupt, recreate it.
- self.connection.close()
+ connection.close()
self.upgrade_db(0)
else:
# fetch db version and upgrade if needed
- version = int(self.cursor.fetchone()[0])
- self.cursor.close()
+ version = int(cursor.fetchone()[0])
+ connection.close()
if version < LocalStatusSQLiteFolder.cur_version:
self.upgrade_db(version)
- self.connection.close()
+
+ def get_cursor(self):
+ """Return a db (connection, cursor) that we can use
+
+ You are responsible for connection.commit() and
+ connection.close() yourself. Connection close() happens
+ automatically when the connection variable is destroyed
+ 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
def upgrade_db(self, from_ver):
"""Upgrade the sqlite format from version 'from_ver' to current"""
@@ -75,21 +93,20 @@ class LocalStatusSQLiteFolder(LocalStatusFolder):
file = open(plaintextfilename, "rt")
line = file.readline().strip()
assert(line == magicline)
- connection = sqlite.connect(self.filename)
- cursor = connection.cursor()
- for line in file.xreadlines():
- line = line.strip()
- uid, flags = line.split(':')
- uid = long(uid)
- flags = [x for x in flags]
- flags.sort()
- flags = ''.join(flags)
- self.cursor.execute('INSERT INTO status (id,flags) VALUES (?,?)',
+ conn, cursor = self.get_cursor()
+ with conn:
+ for line in file.xreadlines():
+ line = line.strip()
+ uid, flags = line.split(':')
+ uid = long(uid)
+ flags = [x for x in flags]
+ flags.sort()
+ flags = ''.join(flags)
+ cursor.execute('INSERT INTO status (id,flags) VALUES (?,?)',
(uid,flags))
+ conn.commit()
file.close()
- self.connection.commit()
os.rename(plaintextfilename, plaintextfilename + ".old")
- self.connection.close()
# Future version upgrades come here...
# if from_ver <= 1: ... #upgrade from 1 to 2
# if from_ver <= 2: ... #upgrade from 2 to 3
@@ -98,12 +115,12 @@ class LocalStatusSQLiteFolder(LocalStatusFolder):
"""Create a new db file"""
self.ui._msg('Creating new Local Status db for %s:%s' \
% (self.repository, self))
- connection = sqlite.connect(self.filename)
- cursor = connection.cursor()
- cursor.execute('CREATE TABLE metadata (key VARCHAR(50) PRIMARY KEY, value VARCHAR(128))')
- cursor.execute("INSERT INTO metadata VALUES('db_version', '1')")
- cursor.execute('CREATE TABLE status (id INTEGER PRIMARY KEY, flags VARCHAR(50))')
- self.save() #commit if needed
+ conn, cursor = self.get_cursor()
+ with conn:
+ cursor.execute('CREATE TABLE metadata (key VARCHAR(50) PRIMARY KEY, value VARCHAR(128))')
+ cursor.execute("INSERT INTO metadata VALUES('db_version', '1')")
+ cursor.execute('CREATE TABLE status (id INTEGER PRIMARY KEY, flags VARCHAR(50))')
+ conn.commit()
def isnewfolder(self):
# testing the existence of the db file won't work. It is created
@@ -113,37 +130,59 @@ class LocalStatusSQLiteFolder(LocalStatusFolder):
def deletemessagelist(self):
"""delete all messages in the db"""
- self.cursor.execute('DELETE FROM status')
+ conn, cursor = self.get_cursor()
+ with conn:
+ cursor.execute('DELETE FROM status')
+ conn.commit()
def cachemessagelist(self):
self.messagelist = {}
- self.cursor.execute('SELECT id,flags from status')
- for row in self.cursor:
- flags = [x for x in row[1]]
- self.messagelist[row[0]] = {'uid': row[0], 'flags': flags}
+ conn, cursor = self.get_cursor()
+ with conn:
+ cursor.execute('SELECT id,flags from status')
+ for row in cursor:
+ flags = [x for x in row[1]]
+ self.messagelist[row[0]] = {'uid': row[0], 'flags': flags}
def save(self):
#Noop in this backend
pass
- def uidexists(self,uid):
- self.cursor.execute('SELECT id FROM status WHERE id=:id',{'id': uid})
- for row in self.cursor:
- if(row[0]==uid):
- return 1
- return 0
-
- def getmessageuidlist(self):
- self.cursor.execute('SELECT id from status')
- r = []
- for row in self.cursor:
- r.append(row[0])
- return r
-
- def getmessagecount(self):
- self.cursor.execute('SELECT count(id) from status');
- row = self.cursor.fetchone()
- return row[0]
+ # 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:
@@ -155,30 +194,36 @@ class LocalStatusSQLiteFolder(LocalStatusFolder):
return uid
self.messagelist[uid] = {'uid': uid, 'flags': flags, 'time': rtime}
- flags.sort()
- flags = ''.join(flags)
- self.cursor.execute('INSERT INTO status (id,flags) VALUES (?,?)',
- (uid,flags))
- self.save()
+ flags = ''.join(sorted(flags))
+ conn, cursor = self.get_cursor()
+ with conn:
+ while True:
+ try:
+ cursor.execute('INSERT INTO status (id,flags) VALUES (?,?)',
+ (uid,flags))
+ conn.commit()
+ except sqlite.OperationalError as e:
+ if e.args[0] != 'database is locked':
+ raise
+ else: #success
+ break
return uid
- def getmessageflags(self, uid):
- self.cursor.execute('SELECT flags FROM status WHERE id=:id',
- {'id': uid})
- for row in self.cursor:
- flags = [x for x in row[0]]
- return flags
- assert False,"getmessageflags() called on non-existing message"
-
- def getmessagetime(self, uid):
- return self.messagelist[uid]['time']
-
def savemessageflags(self, uid, flags):
self.messagelist[uid] = {'uid': uid, 'flags': flags}
flags.sort()
flags = ''.join(flags)
- self.cursor.execute('UPDATE status SET flags=? WHERE id=?',(flags,uid))
- self.save()
+ conn, cursor = self.get_cursor()
+ with conn:
+ while True:
+ try:
+ cursor.execute('UPDATE status SET flags=? WHERE id=?',(flags,uid))
+ conn.commit()
+ except sqlite.OperationalError as e:
+ if e.args[0] != 'database is locked':
+ raise
+ else: #success
+ break
def deletemessages(self, uidlist):
# Weed out ones not in self.messagelist
@@ -186,7 +231,17 @@ class LocalStatusSQLiteFolder(LocalStatusFolder):
if not len(uidlist):
return
- for uid in uidlist:
- del(self.messagelist[uid])
- #if self.uidexists(uid):
- self.cursor.execute('DELETE FROM status WHERE id=:id', {'id': uid})
+ conn, cursor = self.get_cursor()
+ with conn:
+ for uid in uidlist:
+ del(self.messagelist[uid])
+ while True:
+ try:
+ cursor.execute('DELETE FROM status WHERE id=?',
+ uid)
+ conn.commit()
+ except sqlite.OperationalError as e:
+ if e.args[0] != 'database is locked':
+ raise
+ else: #success
+ break
--
1.7.4.1
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