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()?
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http://www.sqlalchemy.org/
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