firebird.py 文件源码

def visit_column(self, column):
        """Firebird supports 'DROP col' instead of 'DROP COLUMN col' syntax

        Drop primary key and unique constraints if dropped column is referencing it."""
        if column.primary_key:
            if column.table.primary_key.columns.contains_column(column):
                column.table.primary_key.drop()
                # TODO: recreate primary key if it references more than this column

        for index in column.table.indexes:
            # "column in index.columns" causes problems as all
            # column objects compare equal and return a SQL expression
            if column.name in [col.name for col in index.columns]:
                index.drop()
                # TODO: recreate index if it references more than this column

        for cons in column.table.constraints:
            if isinstance(cons,PrimaryKeyConstraint):
                # will be deleted only when the column its on
                # is deleted!
                continue

            should_drop = column.name in cons.columns
            if should_drop:
                self.start_alter_table(column)
                self.append("DROP CONSTRAINT ")
                self.append(self.preparer.format_constraint(cons))
                self.execute()
            # TODO: recreate unique constraint if it refenrences more than this column

        self.start_alter_table(column)
        self.append('DROP %s' % self.preparer.format_column(column))
        self.execute()