On Dec 21, 2010, at 8:36 AM, tim wrote:
> Hi,
>
> I have some meta-data columns in my schema. How can I make sure they
> are not part of the SELECT, INSERT and UPDATE statements SQLAlchemy is
> doing in the background?
>
> I tried:
>
>
> Column('lastUpdate', DateTime, DefaultClause('CURRENT_TIMESTAMP'),
> nullable=False), # for Nebula's Syncer
>
>
> along with
>
>
> mapper(Location, locations, version_id_col=locations.c.STAMP,
> exclude_properties=['lastUpdate'], properties = {
> 'site': relation(Site, backref='locations'),
> })
>
>
> But the lastUpdate column still turns up in the SQL it is executing,
> and what's worse, without using it's default value!
>
> Would anyone please help me out?
If the column has an existing server-side default on it, you'd want to specify
server_default=FetchedValue() :
http://www.sqlalchemy.org/docs/core/schema.html#triggered-columns
If you want to "exclude" the column from being used in your application in any
way, simply don't place it in the Table definition. If you're using
reflection, you could use the "include_columns" list on Table to specify which
columns you want.
"exclude_properties" in the ORM prevents those columns from being mapped, but
doesn't prevent the core table level functionality from dealing with this
column so that's why you need to ensure the Table metadata is correct.
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