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from alembic.ddl.impl import DefaultImpl
from alembic import util
#from sqlalchemy.ext.compiler import compiles
#from alembic.ddl.base import AddColumn, alter_table
#from sqlalchemy.schema import AddConstraint
class SQLiteImpl(DefaultImpl):
__dialect__ = 'sqlite'
transactional_ddl = False
"""SQLite supports transactional DDL, but pysqlite does not:
see: http://bugs.python.org/issue10740
"""
def add_constraint(self, const):
# attempt to distinguish between an
# auto-gen constraint and an explicit one
if const._create_rule is None:
raise NotImplementedError(
"No support for ALTER of constraints in SQLite dialect")
elif const._create_rule(self):
util.warn("Skipping unsupported ALTER for "
"creation of implicit constraint")
def drop_constraint(self, const):
if const._create_rule is None:
raise NotImplementedError(
"No support for ALTER of constraints in SQLite dialect")
#@compiles(AddColumn, 'sqlite')
#def visit_add_column(element, compiler, **kw):
# return "%s %s" % (
# alter_table(compiler, element.table_name, element.schema),
# add_column(compiler, element.column, **kw)
# )
#def add_column(compiler, column, **kw):
# text = "ADD COLUMN %s" % compiler.get_column_specification(column, **kw)
# # need to modify SQLAlchemy so that the CHECK associated with a Boolean
# # or Enum gets placed as part of the column constraints, not the Table
# # see ticket 98
# for const in column.constraints:
# text += compiler.process(AddConstraint(const))
# return text
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