django-tidb/django_tidb/tidb/schema.py

from django.db.backends.mysql import schema as myschema


class DatabaseSchemaEditor(myschema.DatabaseSchemaEditor):
    sql_delete_table = "DROP TABLE %(table)s"
    sql_delete_column = "ALTER TABLE %(table)s DROP COLUMN %(column)s"

    def remove_field(self, model, field):
        # Drop any Index, TiDB requires explicite deletion
        if field.db_index:
            idx_names = self._constraint_names(model, [field.column], index=True)
            for idx_name in idx_names:
                self.execute(self._delete_constraint_sql(self.sql_delete_index, model, idx_name))
        super(DatabaseSchemaEditor, self).remove_field(model, field)

    def column_sql(self, model, field, include_default=False):
        """
        Take a field and return its column definition.
        The field must already have had set_attributes_from_name() called.
        """
        # Get the column's type and use that as the basis of the SQL
        db_params = field.db_parameters(connection=self.connection)
        sql = db_params['type']
        params = []
        # Check for fields that aren't actually columns (e.g. M2M)
        if sql is None:
            return None, None
        # Work out nullability
        null = field.null
        # If we were told to include a default value, do so
        include_default = include_default and not self.skip_default(field)
        if include_default:
            default_value = self.effective_default(field)
            if default_value is not None:
                if self.connection.features.requires_literal_defaults:
                    # Some databases can't take defaults as a parameter (oracle)
                    # If this is the case, the individual schema backend should
                    # implement prepare_default
                    sql += " DEFAULT %s" % self.prepare_default(default_value)
                else:
                    sql += " DEFAULT %s"
                    params += [default_value]
        # Oracle treats the empty string ('') as null, so coerce the null
        # option whenever '' is a possible value.
        if (field.empty_strings_allowed and not field.primary_key and
                self.connection.features.interprets_empty_strings_as_nulls):
            null = True
        if null and not self.connection.features.implied_column_null:
            sql += " NULL"
        elif not null:
            sql += " NOT NULL"
        # Primary key/unique outputs
        if field.primary_key:
            sql += " PRIMARY KEY"
        # elif field.unique:
        #     sql += " UNIQUE"
        # Optionally add the tablespace if it's an implicitly indexed column
        tablespace = field.db_tablespace or model._meta.db_tablespace
        if tablespace and self.connection.features.supports_tablespaces and field.unique:
            sql += " %s" % self.connection.ops.tablespace_sql(tablespace, inline=True)
        # Return the sql
        return sql, params