Author: cito
Date: Thu Nov 1 07:40:55 2012
New Revision: 461
Log:
Add transaction handling methods and context managers to pg.
Modified:
trunk/module/pg.py
Modified: trunk/module/pg.py
==============================================================================
--- trunk/module/pg.py Thu Nov 1 07:18:23 2012 (r460)
+++ trunk/module/pg.py Thu Nov 1 07:40:55 2012 (r461)
@@ -29,6 +29,11 @@
except ImportError: # Python < 2.4
pass
try:
+ from contextlib import contextmanager
+except ImportError: # Python < 2.5
+ def contextmanager(f):
+ raise NotImplementedError
+try:
from collections import namedtuple
except ImportError: # Python < 2.6
namedtuple = None
@@ -165,12 +170,13 @@
self._attnames = {}
self._pkeys = {}
self._privileges = {}
+ self._transaction = False
self._args = args, kw
self.debug = None # For debugging scripts, this can be set
# * to a string format specification (e.g. in CGI set to "%s<BR>"),
- # * to a file object to write debug statements,
- # * to a callable object which takes a string argument or
- # * to any other true value to just print debug statements.
+ # * to a file object to write debug statements or
+ # * to a callable object which takes a string argument
+ # * to any other true value to just print debug statements
def __getattr__(self, name):
# All undefined members are same as in underlying pg connection:
@@ -179,6 +185,23 @@
else:
raise _int_error('Connection is not valid')
+ # Context manager methods
+
+ def __enter__(self):
+ if self._transaction:
+ self.begin()
+ return self
+
+ def __exit__(self, typ, val, tb):
+ if self._transaction:
+ self._transaction = None
+ if tb is None:
+ self.commit()
+ else:
+ self.rollback()
+ else:
+ self.close()
+
# Auxiliary methods
def _do_debug(self, s):
@@ -335,6 +358,45 @@
self.db.close()
self.db = db
+ def begin(self, mode=None):
+ """Begin a transaction."""
+ qstr = 'BEGIN'
+ if mode:
+ qstr += ' ' + mode
+ return self.query(qstr)
+
+ start = begin
+
+ def commit(self):
+ """Commit the current transaction."""
+ return self.query('COMMIT')
+
+ end = commit
+
+ def rollback(self, name=None):
+ """Rollback the current transaction."""
+ qstr = 'ROLLBACK'
+ if name:
+ qstr += ' TO ' + name
+ return self.query('ROLLBACK')
+
+ def savepoint(self, name=None):
+ """Define a new savepoint within the current transaction."""
+ qstr = 'SAVEPOINT'
+ if name:
+ qstr += ' ' + name
+ return self.query(qstr)
+
+ def release(self, name):
+ """Destroy a previously defined savepoint."""
+ return self.query('RELEASE ' + name)
+
+ @property
+ def transaction(self):
+ """Return a context manager for running a transaction."""
+ self._transaction = True
+ return self
+
def query(self, qstr, *args):
"""Executes a SQL command string.
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