Yes, the constraints are defined in Python and have names explicitly defined. The CheckConstraint I need to use is defined in a @declared_attr method for the column in a base class from which the mapped class inherits. I did find the CheckConstraint I need in MappedClass.__table__.c.column_name.constraints, but it is not bound to a table, so when I pass it to DropConstraint(), I get:
sqlalchemy.exc.InvalidRequestError: This constraint is not bound to a table. Did you mean to call table.append_constraint(constraint) ? If I pass the the CheckConstraint to MappedClass.__table__.append_constraint(), DropConstraint() works, but I don't understand why I need to explicitly add the constraint to the table. On Friday, November 18, 2016 at 5:11:10 PM UTC-5, Mike Bayer wrote: > > Assuming here your constraints are already defined in Python and we are > not talking about using reflection, we're talking about the CHECK > constraint objects you've already built. If they are defined for a > Table then they would be in table.constraints. If you have them on the > Column then it's true they might only be in column.constraints in that > case. If you're defining them in either place then you'd need to look > in either place. It might be best to go with all table-bound CHECK > constraints as I'm not sure it's as flexible to do add/drop with the > column-level ones. At the very least, constraints need to have an > explicit name in order to support ADD/DROP. > > Alembic's docs get into this a bit here: > http://alembic.zzzcomputing.com/en/latest/naming.html where it talks > about the "naming convention" feature of SQLAlchemy that may or may not > be of use here. > > > > > > On 11/18/2016 04:43 PM, Jonathan Rogers wrote: > > I have a Declarative-instrumented class with several constraints, some > > defined at the table level and some on a column. AFAICT, all the > > constraints are configured correctly because they are rendered correctly > > by CreateTable() when called with the class's Table instance. In order > > to import some data into my carefully designed model, I need to drop > > some constraints, then recreate them NOT VALID. I want to use the > > existing Table instance to execute SQL rather than typing duplicate SQL > > manually. However, I'm having trouble introspecting the Table instance > > to find a specific CheckConstraint defined on a specific column. The > > Table instance's "constraints" property does not contain the constraint > > I need. I can find a CheckConstraint instance in the column's > > "constraints" property but it's not bound to a Table so I can't just > > pass it to DropConstraint(). What is the proper way to get a > > CheckConstraint instance defined on a column that I can pass to > > DropConstraint() and AddConstraint()? > > > > -- > > SQLAlchemy - > > The Python SQL Toolkit and Object Relational Mapper > > > > http://www.sqlalchemy.org/ > > > > To post example code, please provide an MCVE: Minimal, Complete, and > > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > > description. > > --- > > You received this message because you are subscribed to the Google > > Groups "sqlalchemy" group. > > To unsubscribe from this group and stop receiving emails from it, send > > an email to sqlalchemy+...@googlegroups.com <javascript:> > > <mailto:sqlalchemy+unsubscr...@googlegroups.com <javascript:>>. > > To post to this group, send email to sqlal...@googlegroups.com > <javascript:> > > <mailto:sqlal...@googlegroups.com <javascript:>>. > > Visit this group at https://groups.google.com/group/sqlalchemy. > > For more options, visit https://groups.google.com/d/optout. > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
