from typing import List, Set

from sqlalchemy import CheckConstraint

from sqlalchemy.engine import Connectable

from sqlalchemy.sql import ClauseElement

from sqlalchemy.sql.schema import (

ColumnCollectionConstraint, Constraint, ForeignKeyConstraint, Table)

def get_column_names(constraint: ColumnCollectionConstraint) -> List[str]:

return list(constraint.columns.keys())

def get_constraint_sort_key(constraint: Constraint) -> str:

if isinstance(constraint, CheckConstraint):

return f'C{constraint.sqltext}'

elif isinstance(constraint, ColumnCollectionConstraint):

return constraint.__class__.__name__[0] + repr(get_column_names(constraint))

else:

return str(constraint)

def get_compiled_expression(statement: ClauseElement, bind: Connectable) -> str:

"""Return the statement in a form where any placeholders have been filled in."""

return str(statement.compile(bind, compile_kwargs={"literal_binds": True}))

def get_common_fk_constraints(table1: Table, table2: Table) -> Set[ForeignKeyConstraint]:

"""Return a set of foreign key constraints the two tables have against each other."""

c1 = set(c for c in table1.constraints if isinstance(c, ForeignKeyConstraint) and

c.elements[0].column.table == table2)

c2 = set(c for c in table2.constraints if isinstance(c, ForeignKeyConstraint) and

c.elements[0].column.table == table1)

return c1.union(c2)