Hi,
Is there way to map a class to a new table again
mapper(klass, table_1)
mapping the same klass again
mapper(klass, table_2)
already has a primary mapper defined. Use non_primary=True to create a non
primary Mapper. clear_mappers() will remove *all* current mappers from all
classes.
Cannot use clear_mappers(), which will clear other declarative mappings,
Srikanth Bemineni
On Thursday, November 24, 2016 at 10:04:02 PM UTC-6, Srikanth Bemineni
wrote:
>
> Hi,
>
> I am using sqlalchemy in my pyramid application. I have situation here,
> where I need to map a table on the fly in the application during run time.
> I also dont want to re-map all tables, there are some table which are
> defined using a declarative base. I need those mapping to remain as is. How
> can we do this?. Does clear_mappers() remove even declarative base mapping ?
>
>
> DBSession =
> scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
> Base = declarative_base()
>
> class User(Base):
> __tablename__ ="youzer"
> uid = Column(Integer,autoincrement=True, primary_key=True)
> uname = Column(Text,nullable=False,index=True)
>
> Just one of the tables as example. There are many tables that I need to
> map for different request
>
> class GroupOrder()
> gtid = Column(Integer, autoincrement=True,primary_key=True)
> group_id = Column(Integer,
> ForeignKey("group.gid",ondelete="CASCADE"),nullable=False)
> ...
> ...
>
> These groups can grow huge , so decision was made to shard these group
> based on a hash. These are similar structured tables , with different names.
>
> Tables
> group_order_<shard1>
> group_order_<shard1>
> group_order_<shard1>
>
> table_object = Table(<shard table name with similar structure>,
> Base.metadata,
> Column('gtid', Integer, primary_key=True),
> Column('group_id', ForeignKey('group.gid',ondelete="CASCADE"),
> nullable=False),
> ....
> ...
>
>
> Based on the request, I need to map the GroupOrder to the concerned table
> and process the request.
>
> This is a uwsgi application will the clear_mapper affect other worker
> threads. ?
>
> Srikanth Bemineni
>
>
>
>
>
>
>
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