On Sep 18, 2008, at 5:46 AM, Adam Dziendziel wrote:
Hi,
I have a column which contains XML, this XML is parsed when a record
is loaded and object attributes are populated with values from this
XML. When I set an attribute, I would like to mark the XML column
modified (in property() setter). I wouldn't need to serialize all
attributes and assign a new value to the XML column explicitly when
only a single attribute changes. This would generate too much overhead
when I set many attributes subsequently. I'd like to just make the XML
column (or the whole record) dirty, so that I'm able to serialize
attributes to XML only in before_insert/before_update handlers in a
MapperExtension.
Is this possible with SQLAlchemy? I'm using 0.4.x.
This description was very hard to parse, but I think what you're
saying is an attribute changes on a *different* object somewhere,
which you would like to mark the XML-holding object as dirty. To
mark the object dirty you can say instance_state(myobject).modified =
True , where instance_state is in sqlalchemy.orm.attributes.Theres
no dirty flag on individual attributes, the change status is
determined by the contents of the attribute. So just blanking out the
XML attribute until needed is a pretty easy approach here too.Yet
another option which is the most lightweight would be to use a
SessionExtension with an after_flush() method that issues an UPDATE to
the XML-holding column directly.
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