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<div class=Section1>
<p class=MsoNormal>I have only just started to use ZODB and have been able to
use it with ease so far.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I want to be able to have access to multiple ZODB databases
at the same time that are completely independent.<o:p></o:p></p>
<p class=MsoNormal>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.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Can the transactions be made specific to a particular
database or connection?<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Below is example code that accesses two independent databases.<o:p></o:p></p>
<p class=MsoNormal>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.<o:p></o:p></p>
<p class=MsoNormal>The code here commits the changes for both databases.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>How do I stop that happening?<o:p></o:p></p>
<p class=MsoNormal>I am assuming that I need to do something different than
just “<span style='font-size:10.0pt;font-family:"Courier New";color:black'>transaction.commit()”
but what do I need to do?</span><o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Thanks<o:p></o:p></p>
<p class=MsoNormal>Matt<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>##### START CODE<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>from</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> ZODB </span><span style='font-size:
10.0pt;font-family:"Courier New";color:blue'>import</span><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> FileStorage, DB</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>import</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> transaction</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>from</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> persistent </span><span
style='font-size:10.0pt;font-family:"Courier New";color:blue'>import</span><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> Persistent</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>def</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> <b>get_item_root</b>(file_name):</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> </span><span
style='font-size:10.0pt;font-family:"Courier New";color:silver'># open the
database</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> storage =
FileStorage.FileStorage(file_name)</span><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> db = DB(storage)</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> conn = db.open()</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> dbroot = conn.root()</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> </span><span
style='font-size:10.0pt;font-family:"Courier New";color:blue'>return</span><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> dbroot</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>def</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> <b>get_item</b>(dbroot, name):</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> </span><span
style='font-size:10.0pt;font-family:"Courier New";color:blue'>try</span><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>:</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>
item = dbroot[name]</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> </span><span
style='font-size:10.0pt;font-family:"Courier New";color:blue'>except</span><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> KeyError:</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>
item = </span><span style='font-size:10.0pt;font-family:"Courier New";
color:blue'>None</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> </span><span
style='font-size:10.0pt;font-family:"Courier New";color:blue'>return</span><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> item</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>def</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> <b>add_item</b>(dbroot, item):</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> </span><span
style='font-size:10.0pt;font-family:"Courier New";color:blue'>if</span><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> item.name </span><span
style='font-size:10.0pt;font-family:"Courier New";color:blue'>not</span><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> </span><span
style='font-size:10.0pt;font-family:"Courier New";color:blue'>in</span><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> dbroot: </span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>
dbroot[item.name] = item</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> </span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>def</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> <b>save_item</b>(dbroot, item):</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> transaction.commit()</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>class</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> <b>Test</b>(Persistent):</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> </span><span
style='font-size:10.0pt;font-family:"Courier New";color:blue'>def</span><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> <b>__init__</b>(<i>self</i>,
name):</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>
<i>self</i>.name = name</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>
<i>self</i>.value = </span><span style='font-size:10.0pt;font-family:"Courier New";
color:maroon'>0</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>db_1 = get_item_root(</span><i><span
style='font-size:10.0pt;font-family:"Courier New";color:#00AA00'>"db_1"</span></i><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>)</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>db_2 = get_item_root(</span><i><span
style='font-size:10.0pt;font-family:"Courier New";color:#00AA00'>"db_2"</span></i><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>)</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>test_1 = get_item(db_1, </span><i><span
style='font-size:10.0pt;font-family:"Courier New";color:#00AA00'>"test_1"</span></i><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>)</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>if</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> test_1 </span><span style='font-size:
10.0pt;font-family:"Courier New";color:blue'>is</span><span style='font-size:
10.0pt;font-family:"Courier New";color:black'> </span><span style='font-size:
10.0pt;font-family:"Courier New";color:blue'>None</span><span style='font-size:
10.0pt;font-family:"Courier New";color:black'>:</span><span style='font-size:
10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> test_1 = Test(</span><i><span
style='font-size:10.0pt;font-family:"Courier New";color:#00AA00'>"test_1"</span></i><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>)</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> add_item(db_1,
test_1)</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>test_2 = get_item(db_2, </span><i><span
style='font-size:10.0pt;font-family:"Courier New";color:#00AA00'>"test_2"</span></i><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>)</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>if</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> test_2 </span><span style='font-size:
10.0pt;font-family:"Courier New";color:blue'>is</span><span style='font-size:
10.0pt;font-family:"Courier New";color:black'> </span><span style='font-size:
10.0pt;font-family:"Courier New";color:blue'>None</span><span style='font-size:
10.0pt;font-family:"Courier New";color:black'>:</span><span style='font-size:
10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> test_2 = Test(</span><i><span
style='font-size:10.0pt;font-family:"Courier New";color:#00AA00'>"test_2"</span></i><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>)</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> add_item(db_2,
test_2)</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>print</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> </span><i><span style='font-size:10.0pt;
font-family:"Courier New";color:#00AA00'>"BEFORE: test_1: [%s] [%s]"</span></i><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> % (test_1.name,
test_1.value)</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>print</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> </span><i><span style='font-size:10.0pt;
font-family:"Courier New";color:#00AA00'>"BEFORE: test_2: [%s] [%s]"</span></i><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> % (test_2.name,
test_2.value)</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:silver'># increment values</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>test_1.value = test_1.value + </span><span
style='font-size:10.0pt;font-family:"Courier New";color:maroon'>1</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>test_2.value = test_2.value + </span><span
style='font-size:10.0pt;font-family:"Courier New";color:maroon'>1</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>print</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> </span><i><span style='font-size:10.0pt;
font-family:"Courier New";color:#00AA00'>"AFTER: test_1: [%s] [%s]"</span></i><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> % (test_1.name,
test_1.value)</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:blue'>print</span><span style='font-size:10.0pt;
font-family:"Courier New";color:black'> </span><i><span style='font-size:10.0pt;
font-family:"Courier New";color:#00AA00'>"AFTER: test_2: [%s] [%s]"</span></i><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> % (test_2.name,
test_2.value)</span><span style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>save_item(db_1, test_1)</span><span
style='font-size:10.0pt;font-family:"Courier New"'><o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>##### END CODE #####<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
</div>
</body>
</html>
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