""" Extensions to SQLAlchemy for altering existing tables. At the moment, this isn't so much based off of ANSI as much as things that just happen to work with multiple databases. """ import sqlalchemy as sa from sqlalchemy.engine.default import DefaultDialect from sqlalchemy.sql.compiler import SchemaGenerator, SchemaDropper from sqlalchemy.schema import (ForeignKeyConstraint, PrimaryKeyConstraint, CheckConstraint, UniqueConstraint) from migrate.changeset import exceptions, constraint SchemaIterator = sa.engine.SchemaIterator class AlterTableVisitor(SchemaIterator): """Common operations for ``ALTER TABLE`` statements.""" def _to_table(self, param): """Returns the table object for the given param object.""" if isinstance(param, (sa.Column, sa.Index, sa.schema.Constraint)): ret = param.table else: ret = param return ret def start_alter_table(self, param): """Returns the start of an ``ALTER TABLE`` SQL-Statement. Use the param object to determine the table name and use it for building the SQL statement. :param param: object to determine the table from :type param: :class:`sqlalchemy.Column`, :class:`sqlalchemy.Index`, :class:`sqlalchemy.schema.Constraint`, :class:`sqlalchemy.Table`, or string (table name) """ table = self._to_table(param) self.append('\nALTER TABLE %s ' % self.preparer.format_table(table)) return table def _pk_constraint(self, table, column, status): """Create a primary key constraint from a table, column. Status: true if the constraint is being added; false if being dropped """ if isinstance(column, basestring): column = getattr(table.c, name) ret = constraint.PrimaryKeyConstraint(*table.primary_key) if status: # Created PK ret.c.append(column) else: # Dropped PK names = [c.name for c in cons.c] index = names.index(col.name) del ret.c[index] # Allow explicit PK name assignment if isinstance(pk, basestring): ret.name = pk return ret class ANSIColumnGenerator(AlterTableVisitor, SchemaGenerator): """Extends ansisql generator for column creation (alter table add col)""" def visit_column(self, column): """Create a column (table already exists). :param column: column object :type column: :class:`sqlalchemy.Column` instance """ table = self.start_alter_table(column) self.append("ADD ") colspec = self.get_column_specification(column) self.append(colspec) self.execute() # add in foreign keys if column.foreign_keys: self.visit_alter_foriegn_keys(column) def visit_alter_foriegn_keys(self, column): for fk in column.foreign_keys: self.define_foreign_key(fk.constraint) def visit_table(self, table): """Default table visitor, does nothing. :param table: table object :type table: :class:`sqlalchemy.Table` instance """ pass class ANSIColumnDropper(AlterTableVisitor, SchemaDropper): """Extends ANSI SQL dropper for column dropping (``ALTER TABLE DROP COLUMN``). """ def visit_column(self, column): """Drop a column from its table. :param column: the column object :type column: :class:`sqlalchemy.Column` """ table = self.start_alter_table(column) self.append(' DROP COLUMN %s' % self.preparer.format_column(column)) self.execute() class ANSISchemaChanger(AlterTableVisitor, SchemaGenerator): """Manages changes to existing schema elements. Note that columns are schema elements; ``ALTER TABLE ADD COLUMN`` is in SchemaGenerator. All items may be renamed. Columns can also have many of their properties - type, for example - changed. Each function is passed a tuple, containing (object, name); where object is a type of object you'd expect for that function (ie. table for visit_table) and name is the object's new name. NONE means the name is unchanged. """ def visit_table(self, table): """Rename a table. Other ops aren't supported.""" self.start_alter_table(table) self.append("RENAME TO %s" % self.preparer.quote(table.new_name, table.quote)) self.execute() def visit_index(self, index): """Rename an index""" self.append("ALTER INDEX %s RENAME TO %s" % (self.preparer.quote(self._validate_identifier(index.name, True), index.quote), self.preparer.quote(self._validate_identifier(index.new_name, True) , index.quote))) self.execute() def visit_column(self, column): """Rename/change a column.""" # ALTER COLUMN is implemented as several ALTER statements delta = column.delta keys = delta.keys() if 'type' in keys: self._run_subvisit(delta, self._visit_column_type) if 'nullable' in keys: self._run_subvisit(delta, self._visit_column_nullable) if 'server_default' in keys: # Skip 'default': only handle server-side defaults, others # are managed by the app, not the db. self._run_subvisit(delta, self._visit_column_default) if 'name' in keys: self._run_subvisit(delta, self._visit_column_name) def _run_subvisit(self, delta, func): """Runs visit method based on what needs to be changed on column""" table = self._to_table(delta.table) col_name = delta.current_name ret = func(table, col_name, delta) self.execute() def _visit_column_foreign_key(self, delta): table = delta.table column = getattr(table.c, delta.current_name) cons = constraint.ForeignKeyConstraint(column, autoload=True) fk = delta['foreign_key'] if fk: # For now, cons.columns is limited to one column: # no multicolumn FKs column.foreign_key = ForeignKey(*cons.columns) else: column_foreign_key = None cons.drop() cons.create() def _visit_column_primary_key(self, delta): table = delta.table col = getattr(table.c, delta.current_name) pk = delta['primary_key'] cons = self._pk_constraint(table, col, pk) cons.drop() cons.create() def _visit_column_nullable(self, table, col_name, delta): nullable = delta['nullable'] table = self._to_table(table) self.start_alter_table(table) # TODO: use preparer.format_column self.append("ALTER COLUMN %s " % self.preparer.quote_identifier(col_name)) if nullable: self.append("DROP NOT NULL") else: self.append("SET NOT NULL") def _visit_column_default(self, table, col_name, delta): server_default = delta['server_default'] # Dummy column: get_col_default_string needs a column for some # reason dummy = sa.Column(None, None, server_default=server_default) default_text = self.get_column_default_string(dummy) self.start_alter_table(table) # TODO: use preparer.format_column self.append("ALTER COLUMN %s " % self.preparer.quote_identifier(col_name)) if default_text is not None: self.append("SET DEFAULT %s" % default_text) else: self.append("DROP DEFAULT") def _visit_column_type(self, table, col_name, delta): type_ = delta['type'] if not isinstance(type_, sa.types.AbstractType): # It's the class itself, not an instance... make an # instance type_ = type_() type_text = type_.dialect_impl(self.dialect).get_col_spec() self.start_alter_table(table) # TODO: does type need formating? # TODO: use preparer.format_column self.append("ALTER COLUMN %s TYPE %s" % (self.preparer.quote_identifier(col_name), type_text)) def _visit_column_name(self, table, col_name, delta): new_name = delta['name'] self.start_alter_table(table) # TODO: use preparer.format_column self.append('RENAME COLUMN %s TO %s' % \ (self.preparer.quote_identifier(col_name), self.preparer.quote_identifier(new_name))) class ANSIConstraintCommon(AlterTableVisitor): """ Migrate's constraints require a separate creation function from SA's: Migrate's constraints are created independently of a table; SA's are created at the same time as the table. """ def get_constraint_name(self, cons): """Gets a name for the given constraint. If the name is already set it will be used otherwise the constraint's :meth:`autoname ` method is used. :param cons: constraint object """ if cons.name is not None: ret = cons.name else: ret = cons.name = cons.autoname() return self.preparer.quote(ret, cons.quote) def visit_migrate_primary_key_constraint(self, *p, **k): self._visit_constraint(*p, **k) def visit_migrate_foreign_key_constraint(self, *p, **k): self._visit_constraint(*p, **k) def visit_migrate_check_constraint(self, *p, **k): self._visit_constraint(*p, **k) def visit_migrate_unique_constraint(self, *p, **k): self._visit_constraint(*p, **k) class ANSIConstraintGenerator(ANSIConstraintCommon, SchemaGenerator): def get_constraint_specification(self, cons, **kwargs): """Constaint SQL generators. We cannot use SA visitors because they append comma. """ if isinstance(cons, PrimaryKeyConstraint): if cons.name is not None: self.append("CONSTRAINT %s " % self.preparer.format_constraint(cons)) self.append("PRIMARY KEY ") self.append("(%s)" % ', '.join(self.preparer.quote(c.name, c.quote) for c in cons)) self.define_constraint_deferrability(cons) elif isinstance(cons, ForeignKeyConstraint): self.define_foreign_key(cons) elif isinstance(cons, CheckConstraint): if cons.name is not None: self.append("CONSTRAINT %s " % self.preparer.format_constraint(cons)) self.append(" CHECK (%s)" % cons.sqltext) self.define_constraint_deferrability(cons) elif isinstance(cons, UniqueConstraint): if cons.name is not None: self.append("CONSTRAINT %s " % self.preparer.format_constraint(cons)) self.append(" UNIQUE (%s)" % \ (', '.join(self.preparer.quote(c.name, c.quote) for c in cons))) self.define_constraint_deferrability(cons) else: raise exceptions.InvalidConstraintError(cons) def _visit_constraint(self, constraint): table = self.start_alter_table(constraint) constraint.name = self.get_constraint_name(constraint) self.append("ADD ") self.get_constraint_specification(constraint) self.execute() class ANSIConstraintDropper(ANSIConstraintCommon, SchemaDropper): def _visit_constraint(self, constraint): self.start_alter_table(constraint) self.append("DROP CONSTRAINT ") self.append(self.get_constraint_name(constraint)) if constraint.cascade: self.append(" CASCADE") self.execute() class ANSIDialect(DefaultDialect): columngenerator = ANSIColumnGenerator columndropper = ANSIColumnDropper schemachanger = ANSISchemaChanger constraintgenerator = ANSIConstraintGenerator constraintdropper = ANSIConstraintDropper