I have only just started to use ZODB and have been able to use it with
ease so far.


I want to be able to have access to multiple ZODB databases at the same
time that are completely independent.

What I cannot see how to do is to keep the changes to the objects from
each database separate - that is making the transaction commits only
occur for one database at a time even if changes have occurred to
multiple databases between commits.


Can the transactions be made specific to a particular database or


Below is example code that accesses two independent databases.

It opens the databases, increments the value for an object in each
database, but I only want to commit the changes to one of databases.

The code here commits the changes for both databases.


How do I stop that happening?

I am assuming that I need to do something different than just
"transaction.commit()" but what do I need to do?








from ZODB import FileStorage, DB

import transaction


from persistent import Persistent



def get_item_root(file_name):

    # open the database

    storage = FileStorage.FileStorage(file_name)

    db = DB(storage)

    conn = db.open()

    dbroot = conn.root()

    return dbroot


def get_item(dbroot, name):


        item = dbroot[name]

    except KeyError:

        item = None

    return item


def add_item(dbroot, item):

    if item.name not in dbroot: 

        dbroot[item.name] = item


def save_item(dbroot, item):



class Test(Persistent):

    def __init__(self, name):

        self.name = name

        self.value = 0



db_1 = get_item_root("db_1")

db_2 = get_item_root("db_2")


test_1 = get_item(db_1, "test_1")

if test_1 is None:

    test_1 = Test("test_1")

    add_item(db_1, test_1)


test_2 = get_item(db_2, "test_2")

if test_2 is None:

    test_2 = Test("test_2")

    add_item(db_2, test_2)


print "BEFORE: test_1: [%s] [%s]" % (test_1.name, test_1.value)

print "BEFORE: test_2: [%s] [%s]" % (test_2.name, test_2.value)


# increment values

test_1.value = test_1.value + 1

test_2.value = test_2.value + 1

print "AFTER: test_1: [%s] [%s]" % (test_1.name, test_1.value)

print "AFTER: test_2: [%s] [%s]" % (test_2.name, test_2.value)


save_item(db_1, test_1)



##### END CODE #####


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