stevazi/addon
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases 3 Wiki Activity

test db con sqlitedict

Browse Source
This commit is contained in:
mac12m99
2021-02-02 22:41:10 +01:00
parent e62f9fd51d
commit c07558e545
5 changed files with 640 additions and 122 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/sqlitedict.py
+601
View File
@@ -0,0 +1,601 @@
#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# This code is distributed under the terms and conditions
# from the Apache License, Version 2.0
#
# http://opensource.org/licenses/apache2.0.php
#
# This code was inspired by:
# * http://code.activestate.com/recipes/576638-draft-for-an-sqlite3-based-dbm/
# * http://code.activestate.com/recipes/526618/
"""
A lightweight wrapper around Python's sqlite3 database, with a dict-like interface
and multi-thread access support::
>>> mydict = SqliteDict('some.db', autocommit=True) # the mapping will be persisted to file `some.db`
>>> mydict['some_key'] = any_picklable_object
>>> print mydict['some_key']
>>> print len(mydict) # etc... all dict functions work
Pickle is used internally to serialize the values. Keys are strings.
If you don't use autocommit (default is no autocommit for performance), then
don't forget to call `mydict.commit()` when done with a transaction.
"""
import sqlite3
import os
import sys
import tempfile
import logging
import time
import traceback
from threading import Thread
__version__ = '1.7.0.dev0'
major_version = sys.version_info[0]
if major_version < 3: # py <= 2.x
if sys.version_info[1] < 5: # py <= 2.4
raise ImportError("sqlitedict requires python 2.5 or higher (python 3.3 or higher supported)")
# necessary to use exec()_ as this would be a SyntaxError in python3.
# this is an exact port of six.reraise():
def exec_(_code_, _globs_=None, _locs_=None):
"""Execute code in a namespace."""
if _globs_ is None:
frame = sys._getframe(1)
_globs_ = frame.f_globals
if _locs_ is None:
_locs_ = frame.f_locals
del frame
elif _locs_ is None:
_locs_ = _globs_
exec("""exec _code_ in _globs_, _locs_""")
class TimeoutError(OSError):
pass
exec_("def reraise(tp, value, tb=None):\n"
" raise tp, value, tb\n")
else:
def reraise(tp, value, tb=None):
if value is None:
value = tp()
if value.__traceback__ is not tb:
raise value.with_traceback(tb)
raise value
try:
from cPickle import dumps, loads, HIGHEST_PROTOCOL as PICKLE_PROTOCOL
except ImportError:
from pickle import dumps, loads, HIGHEST_PROTOCOL as PICKLE_PROTOCOL
# some Python 3 vs 2 imports
try:
from collections import UserDict as DictClass
except ImportError:
from UserDict import DictMixin as DictClass
try:
from queue import Queue
except ImportError:
from Queue import Queue
logger = logging.getLogger(__name__)
def open(*args, **kwargs):
"""See documentation of the SqliteDict class."""
return SqliteDict(*args, **kwargs)
def encode(obj):
"""Serialize an object using pickle to a binary format accepted by SQLite."""
return sqlite3.Binary(dumps(obj, protocol=PICKLE_PROTOCOL))
def decode(obj):
"""Deserialize objects retrieved from SQLite."""
return loads(bytes(obj))
class SqliteDict(DictClass):
VALID_FLAGS = ['c', 'r', 'w', 'n']
def __init__(self, filename=None, tablename='unnamed', flag='c',
autocommit=False, journal_mode="DELETE", encode=encode, decode=decode, timeout=5):
"""
Initialize a thread-safe sqlite-backed dictionary. The dictionary will
be a table `tablename` in database file `filename`. A single file (=database)
may contain multiple tables.
If no `filename` is given, a random file in temp will be used (and deleted
from temp once the dict is closed/deleted).
If you enable `autocommit`, changes will be committed after each operation
(more inefficient but safer). Otherwise, changes are committed on `self.commit()`,
`self.clear()` and `self.close()`.
Set `journal_mode` to 'OFF' if you're experiencing sqlite I/O problems
or if you need performance and don't care about crash-consistency.
The `flag` parameter. Exactly one of:
'c': default mode, open for read/write, creating the db/table if necessary.
'w': open for r/w, but drop `tablename` contents first (start with empty table)
'r': open as read-only
'n': create a new database (erasing any existing tables, not just `tablename`!).
The `encode` and `decode` parameters are used to customize how the values
are serialized and deserialized.
The `encode` parameter must be a function that takes a single Python
object and returns a serialized representation.
The `decode` function must be a function that takes the serialized
representation produced by `encode` and returns a deserialized Python
object.
The default is to use pickle.
The `timeout` defines the maximum time (in seconds) to wait for initial Thread startup.
"""
self.in_temp = filename is None
if self.in_temp:
fd, filename = tempfile.mkstemp(prefix='sqldict')
os.close(fd)
if flag not in SqliteDict.VALID_FLAGS:
raise RuntimeError("Unrecognized flag: %s" % flag)
self.flag = flag
if flag == 'n':
if os.path.exists(filename):
os.remove(filename)
dirname = os.path.dirname(filename)
if dirname:
if not os.path.exists(dirname):
raise RuntimeError('Error! The directory does not exist, %s' % dirname)
self.filename = filename
# Use standard SQL escaping of double quote characters in identifiers, by doubling them.
# See https://github.com/RaRe-Technologies/sqlitedict/pull/113
self.tablename = tablename.replace('"', '""')
self.autocommit = autocommit
self.journal_mode = journal_mode
self.encode = encode
self.decode = decode
self.timeout = timeout
logger.info("opening Sqlite table %r in %r" % (tablename, filename))
self.conn = self._new_conn()
if self.flag == 'r':
if self.tablename not in SqliteDict.get_tablenames(self.filename):
msg = 'Refusing to create a new table "%s" in read-only DB mode' % tablename
raise RuntimeError(msg)
else:
MAKE_TABLE = 'CREATE TABLE IF NOT EXISTS "%s" (key TEXT PRIMARY KEY, value BLOB)' % self.tablename
self.conn.execute(MAKE_TABLE)
self.conn.commit()
if flag == 'w':
self.clear()
def _new_conn(self):
return SqliteMultithread(self.filename, autocommit=self.autocommit, journal_mode=self.journal_mode,
timeout=self.timeout)
def __enter__(self):
if not hasattr(self, 'conn') or self.conn is None:
self.conn = self._new_conn()
return self
def __exit__(self, *exc_info):
self.close()
def __str__(self):
return "SqliteDict(%s)" % (self.filename)
def __repr__(self):
return str(self) # no need of something complex
def __len__(self):
# `select count (*)` is super slow in sqlite (does a linear scan!!)
# As a result, len() is very slow too once the table size grows beyond trivial.
# We could keep the total count of rows ourselves, by means of triggers,
# but that seems too complicated and would slow down normal operation
# (insert/delete etc).
GET_LEN = 'SELECT COUNT(*) FROM "%s"' % self.tablename
rows = self.conn.select_one(GET_LEN)[0]
return rows if rows is not None else 0
def __bool__(self):
# No elements is False, otherwise True
GET_MAX = 'SELECT MAX(ROWID) FROM "%s"' % self.tablename
m = self.conn.select_one(GET_MAX)[0]
# Explicit better than implicit and bla bla
return True if m is not None else False
def iterkeys(self):
GET_KEYS = 'SELECT key FROM "%s" ORDER BY rowid' % self.tablename
for key in self.conn.select(GET_KEYS):
yield key[0]
def itervalues(self):
GET_VALUES = 'SELECT value FROM "%s" ORDER BY rowid' % self.tablename
for value in self.conn.select(GET_VALUES):
yield self.decode(value[0])
def iteritems(self):
GET_ITEMS = 'SELECT key, value FROM "%s" ORDER BY rowid' % self.tablename
for key, value in self.conn.select(GET_ITEMS):
yield key, self.decode(value)
def keys(self):
return self.iterkeys() if major_version > 2 else list(self.iterkeys())
def values(self):
return self.itervalues() if major_version > 2 else list(self.itervalues())
def items(self):
return self.iteritems() if major_version > 2 else list(self.iteritems())
def __contains__(self, key):
HAS_ITEM = 'SELECT 1 FROM "%s" WHERE key = ?' % self.tablename
return self.conn.select_one(HAS_ITEM, (key,)) is not None
def __getitem__(self, key):
GET_ITEM = 'SELECT value FROM "%s" WHERE key = ?' % self.tablename
item = self.conn.select_one(GET_ITEM, (key,))
if item is None:
raise KeyError(key)
return self.decode(item[0])
def __setitem__(self, key, value):
if self.flag == 'r':
raise RuntimeError('Refusing to write to read-only SqliteDict')
ADD_ITEM = 'REPLACE INTO "%s" (key, value) VALUES (?,?)' % self.tablename
self.conn.execute(ADD_ITEM, (key, self.encode(value)))
if self.autocommit:
self.commit()
def __delitem__(self, key):
if self.flag == 'r':
raise RuntimeError('Refusing to delete from read-only SqliteDict')
if key not in self:
raise KeyError(key)
DEL_ITEM = 'DELETE FROM "%s" WHERE key = ?' % self.tablename
self.conn.execute(DEL_ITEM, (key,))
if self.autocommit:
self.commit()
def update(self, items=(), **kwds):
if self.flag == 'r':
raise RuntimeError('Refusing to update read-only SqliteDict')
try:
items = items.items()
except AttributeError:
pass
items = [(k, self.encode(v)) for k, v in items]
UPDATE_ITEMS = 'REPLACE INTO "%s" (key, value) VALUES (?, ?)' % self.tablename
self.conn.executemany(UPDATE_ITEMS, items)
if kwds:
self.update(kwds)
if self.autocommit:
self.commit()
def __iter__(self):
return self.iterkeys()
def clear(self):
if self.flag == 'r':
raise RuntimeError('Refusing to clear read-only SqliteDict')
# avoid VACUUM, as it gives "OperationalError: database schema has changed"
CLEAR_ALL = 'DELETE FROM "%s";' % self.tablename
self.conn.commit()
self.conn.execute(CLEAR_ALL)
self.conn.commit()
@staticmethod
def get_tablenames(filename):
"""get the names of the tables in an sqlite db as a list"""
if not os.path.isfile(filename):
raise IOError('file %s does not exist' % (filename))
GET_TABLENAMES = 'SELECT name FROM sqlite_master WHERE type="table"'
with sqlite3.connect(filename) as conn:
cursor = conn.execute(GET_TABLENAMES)
res = cursor.fetchall()
return [name[0] for name in res]
def commit(self, blocking=True):
"""
Persist all data to disk.
When `blocking` is False, the commit command is queued, but the data is
not guaranteed persisted (default implication when autocommit=True).
"""
if self.conn is not None:
self.conn.commit(blocking)
sync = commit
def close(self, do_log=True, force=False):
if do_log:
logger.debug("closing %s" % self)
if hasattr(self, 'conn') and self.conn is not None:
if self.conn.autocommit and not force:
# typically calls to commit are non-blocking when autocommit is
# used. However, we need to block on close() to ensure any
# awaiting exceptions are handled and that all data is
# persisted to disk before returning.
self.conn.commit(blocking=True)
self.conn.close(force=force)
self.conn = None
if self.in_temp:
try:
os.remove(self.filename)
except Exception:
pass
def terminate(self):
"""Delete the underlying database file. Use with care."""
if self.flag == 'r':
raise RuntimeError('Refusing to terminate read-only SqliteDict')
self.close()
if self.filename == ':memory:':
return
logger.info("deleting %s" % self.filename)
try:
if os.path.isfile(self.filename):
os.remove(self.filename)
except (OSError, IOError):
logger.exception("failed to delete %s" % (self.filename))
def __del__(self):
# like close(), but assume globals are gone by now (do not log!)
try:
self.close(do_log=False, force=True)
except Exception:
# prevent error log flood in case of multiple SqliteDicts
# closed after connection lost (exceptions are always ignored
# in __del__ method.
pass
# Adding extra methods for python 2 compatibility (at import time)
if major_version == 2:
SqliteDict.__nonzero__ = SqliteDict.__bool__
del SqliteDict.__bool__ # not needed and confusing
class SqliteMultithread(Thread):
"""
Wrap sqlite connection in a way that allows concurrent requests from multiple threads.
This is done by internally queueing the requests and processing them sequentially
in a separate thread (in the same order they arrived).
"""
def __init__(self, filename, autocommit, journal_mode, timeout):
super(SqliteMultithread, self).__init__()
self.filename = filename
self.autocommit = autocommit
self.journal_mode = journal_mode
# use request queue of unlimited size
self.reqs = Queue()
self.setDaemon(True) # python2.5-compatible
self.exception = None
self._sqlitedict_thread_initialized = None
self.timeout = timeout
self.log = logging.getLogger('sqlitedict.SqliteMultithread')
self.start()
def run(self):
try:
if self.autocommit:
conn = sqlite3.connect(self.filename, isolation_level=None, check_same_thread=False)
else:
conn = sqlite3.connect(self.filename, check_same_thread=False)
except Exception:
self.log.exception("Failed to initialize connection for filename: %s" % self.filename)
self.exception = sys.exc_info()
raise
try:
conn.execute('PRAGMA journal_mode = %s' % self.journal_mode)
conn.text_factory = str
cursor = conn.cursor()
conn.commit()
cursor.execute('PRAGMA synchronous=OFF')
except Exception:
self.log.exception("Failed to execute PRAGMA statements.")
self.exception = sys.exc_info()
raise
self._sqlitedict_thread_initialized = True
res = None
while True:
req, arg, res, outer_stack = self.reqs.get()
if req == '--close--':
assert res, ('--close-- without return queue', res)
break
elif req == '--commit--':
conn.commit()
if res:
res.put('--no more--')
else:
try:
cursor.execute(req, arg)
except Exception:
self.exception = (e_type, e_value, e_tb) = sys.exc_info()
inner_stack = traceback.extract_stack()
# An exception occurred in our thread, but we may not
# immediately able to throw it in our calling thread, if it has
# no return `res` queue: log as level ERROR both the inner and
# outer exception immediately.
#
# Any iteration of res.get() or any next call will detect the
# inner exception and re-raise it in the calling Thread; though
# it may be confusing to see an exception for an unrelated
# statement, an ERROR log statement from the 'sqlitedict.*'
# namespace contains the original outer stack location.
self.log.error('Inner exception:')
for item in traceback.format_list(inner_stack):
self.log.error(item)
self.log.error('') # deliniate traceback & exception w/blank line
for item in traceback.format_exception_only(e_type, e_value):
self.log.error(item)
self.log.error('') # exception & outer stack w/blank line
self.log.error('Outer stack:')
for item in traceback.format_list(outer_stack):
self.log.error(item)
self.log.error('Exception will be re-raised at next call.')
if res:
for rec in cursor:
res.put(rec)
res.put('--no more--')
if self.autocommit:
conn.commit()
self.log.debug('received: %s, send: --no more--', req)
conn.close()
res.put('--no more--')
def check_raise_error(self):
"""
Check for and raise exception for any previous sqlite query.
For the `execute*` family of method calls, such calls are non-blocking and any
exception raised in the thread cannot be handled by the calling Thread (usually
MainThread). This method is called on `close`, and prior to any subsequent
calls to the `execute*` methods to check for and raise an exception in a
previous call to the MainThread.
"""
if self.exception:
e_type, e_value, e_tb = self.exception
# clear self.exception, if the caller decides to handle such
# exception, we should not repeatedly re-raise it.
self.exception = None
self.log.error('An exception occurred from a previous statement, view '
'the logging namespace "sqlitedict" for outer stack.')
# The third argument to raise is the traceback object, and it is
# substituted instead of the current location as the place where
# the exception occurred, this is so that when using debuggers such
# as `pdb', or simply evaluating the naturally raised traceback, we
# retain the original (inner) location of where the exception
# occurred.
reraise(e_type, e_value, e_tb)
def execute(self, req, arg=None, res=None):
"""
`execute` calls are non-blocking: just queue up the request and return immediately.
"""
self._wait_for_initialization()
self.check_raise_error()
# NOTE: This might be a lot of information to pump into an input
# queue, affecting performance. I've also seen earlier versions of
# jython take a severe performance impact for throwing exceptions
# so often.
stack = traceback.extract_stack()[:-1]
self.reqs.put((req, arg or tuple(), res, stack))
def executemany(self, req, items):
for item in items:
self.execute(req, item)
self.check_raise_error()
def select(self, req, arg=None):
"""
Unlike sqlite's native select, this select doesn't handle iteration efficiently.
The result of `select` starts filling up with values as soon as the
request is dequeued, and although you can iterate over the result normally
(`for res in self.select(): ...`), the entire result will be in memory.
"""
res = Queue() # results of the select will appear as items in this queue
self.execute(req, arg, res)
while True:
rec = res.get()
self.check_raise_error()
if rec == '--no more--':
break
yield rec
def select_one(self, req, arg=None):
"""Return only the first row of the SELECT, or None if there are no matching rows."""
try:
return next(iter(self.select(req, arg)))
except StopIteration:
return None
def commit(self, blocking=True):
if blocking:
# by default, we await completion of commit() unless
# blocking=False. This ensures any available exceptions for any
# previous statement are thrown before returning, and that the
# data has actually persisted to disk!
self.select_one('--commit--')
else:
# otherwise, we fire and forget as usual.
self.execute('--commit--')
def close(self, force=False):
if force:
# If a SqliteDict is being killed or garbage-collected, then select_one()
# could hang forever because run() might already have exited and therefore
# can't process the request. Instead, push the close command to the requests
# queue directly. If run() is still alive, it will exit gracefully. If not,
# then there's nothing we can do anyway.
self.reqs.put(('--close--', None, Queue(), None))
else:
# we abuse 'select' to "iter" over a "--close--" statement so that we
# can confirm the completion of close before joining the thread and
# returning (by semaphore '--no more--'
self.select_one('--close--')
self.join()
def _wait_for_initialization(self):
"""
Polls the 'initialized' flag to be set by the started Thread in run().
"""
# A race condition may occur without waiting for initialization:
# __init__() finishes with the start() call, but the Thread needs some time to actually start working.
# If opening the database file fails in run(), an exception will occur and self.exception will be set.
# But if we run check_raise_error() before run() had a chance to set self.exception, it will report
# a false negative: An exception occured and the thread terminates but self.exception is unset.
# This leads to a deadlock while waiting for the results of execute().
# By waiting for the Thread to set the initialized flag, we can ensure the thread has successfully
# opened the file - and possibly set self.exception to be detected by check_raise_error().
start_time = time.time()
while time.time() - start_time < self.timeout:
if self._sqlitedict_thread_initialized or self.exception:
return
time.sleep(0.1)
raise TimeoutError("SqliteMultithread failed to flag initialization withing %0.0f seconds." % self.timeout)
if __name__ == '__main__':
print(__version__)