Source code for soma.sqlite_tools

# -*- coding: utf-8 -*-

#  This software and supporting documentation are distributed by
#      Institut Federatif de Recherche 49
#      CEA/NeuroSpin, Batiment 145,
#      91191 Gif-sur-Yvette cedex
#      France
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# This software is governed by the CeCILL-B license under
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'''
This module contains functions and classes related to sqlite databases.

* author: Yann Cointepas
* organization: NeuroSpin
* license: `CeCILL B <http://www.cecill.info/licences/Licence_CeCILL-B_V1-en.html>`_
'''
from __future__ import absolute_import
from __future__ import print_function
__docformat__ = "restructuredtext en"


import sys
import threading
import sqlite3

#------------------------------------------------------------------------------


[docs]class ThreadSafeSQLiteConnection(object): ''' Python wrapping of SQLite do not allow sharing of database connection between threads. This class allows to automatically create a connection for each thread. ''' _currentId = 0 _classLock = threading.RLock() def __init__(self, *args, **kwargs): ''' A ThreadSafeSQLiteConnection is created with the parameters that would be used for a call to sqlite3.connect() in a single thread system. These parameters are stored to allow to create a separate SQLite connection for any thread with get_connection(). ''' super(ThreadSafeSQLiteConnection, self).__init__() self.__args = args self.__kwargs = kwargs self._instanceLock = threading.RLock() self.connections = {} self._classLock.acquire() try: self._id = ThreadSafeSQLiteConnection._currentId ThreadSafeSQLiteConnection._currentId += 1 finally: self._classLock.release() def __del__(self): if threading is None: # The interpretor is exiting and we cannot access threading # module. We cannot do anything. return if self.__args is not None: sqliteFile = self.__args[0] self.close() for thread in self.connections.keys(): connection, connectionClosed = self.connections[thread] if connection is not None: currentThread = threading.currentThread().getName() print('WARNING: internal error: an sqlite connection on', repr(sqliteFile), 'is opened for thread', thread, 'but the corresponding ThreadSafeSQLiteConnection instance (number ' + str(self._id) + ') is being deleted in thread', currentThread + '. Method currentThreadCleanup() should have been called from', thread, 'to supress this warning.', file=sys.stderr)
[docs] def get_connection(self): ''' Returns a SQLite connection (i.e. the result of sqlite3.connect) for the current thread. If it does not already exists, it is created and stored for the current thread. In order to destroy this connection it is necessary to call self.delete_connection() from the current thread. If a ThreadSafeSQLiteConnection is destroyed in a thread, all connections opened in other threads must have been deleted. ''' if self.__args is None: raise RuntimeError( 'Attempt to access to a closed ThreadSafeSQLiteConnection') currentThread = threading.currentThread().getName() # print('!ThreadSafeSQLiteConnection:' + currentThread + '!') # _getConnection( id =', self._id, ')', self.__args self._instanceLock.acquire() try: # currentThreadConnections = self.connections.setdefault( currentThread, {} ) # print('!ThreadSafeSQLiteConnection:' + currentThread + '!') # currentThreadConnections =', currentThreadConnections connection, connectionClosed = self.connections.get( currentThread, (None, True)) if connectionClosed: if connection is not None: connection.close() connection = sqlite3.connect(*self.__args, **self.__kwargs) # print('!ThreadSafeSQLiteConnection:' + currentThread + '!' # opened', connection) self.connections[currentThread] = (connection, False) finally: self._instanceLock.release() return connection
[docs] def delete_connection(self): ''' Delete the connection previously created for the current thread with get_connection() ''' if threading.currentThread is None: # exiting, threading attributes have become None return currentThread = threading.currentThread().getName() self._instanceLock.acquire() try: connection, connectionClosed = self.connections.pop( currentThread, (None, True)) finally: self._instanceLock.release() if connection is not None: connection.close()
[docs] def close(self): ''' After this call no more connection can be opened ''' if self.__args is not None: self.closeSqliteConnections() self.__args = None self.__kwargs = None
[docs] def close_connections(self): ''' Mark the opened connection for all the threads as closed. Subsequent calls to get_connection() will have to recreate the sqlite connection with sqlite3.connect(). This method does not delete the connection of the current thread. ''' if self.__args is not None: if threading.currentThread is None: # exiting, threading attributes have become None return self.currentThreadCleanup() currentThread = threading.currentThread().getName() self._instanceLock.acquire() try: for thread in self.connections.keys(): connection, connectionClosed = self.connections[thread] self.connections[thread] = (connection, True) finally: self._instanceLock.release()
# For backward compatibility _getConnection = get_connection currentThreadCleanup = delete_connection closeSqliteConnections = close_connections