"""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.base import Connection, Dialect from sqlalchemy.sql.compiler import SchemaGenerator from migrate.changeset import constraint,exceptions SchemaIterator = sa.engine.SchemaIterator class RawAlterTableVisitor(object): """Common operations for 'alter table' statements""" def _to_table(self,param): if isinstance(param,(sa.Column,sa.Index,sa.schema.Constraint)): ret = param.table else: ret = param return ret def _to_table_name(self,param): ret = self._to_table(param) if isinstance(ret,sa.Table): ret = ret.fullname return ret def start_alter_table(self,param): table = self._to_table(param) table_name = self._to_table_name(table) self.append('\nALTER TABLE "%s" ' % table_name) 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 #cons.remove(col) 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 AlterTableVisitor(SchemaIterator,RawAlterTableVisitor): """Common operations for 'alter table' statements""" class ANSIColumnGenerator(AlterTableVisitor,SchemaGenerator): """Extends ansisql generator for column creation (alter table add col)""" #def __init__(self, *args, **kwargs): # dialect = None # if isinstance(args[0], Connection): # dialect = args[0].engine.dialect # elif isinstance(args[0], Dialect): # dialect = args[0] # else: # raise exceptions.Error("Cannot infer dialect in __init__") # super(ANSIColumnGenerator, self).__init__(dialect, *args, # **kwargs) def visit_column(self,column): """Create a column (table already exists); #32""" table = self.start_alter_table(column) self.append(" ADD ") pks = table.primary_key colspec = self.get_column_specification(column) self.append(colspec) self.execute() #if column.primary_key: # cons = self._pk_constraint(table,column,True) # cons.drop() # cons.create() def visit_table(self,table): pass class ANSIColumnDropper(AlterTableVisitor): """Extends ansisql dropper for column dropping (alter table drop col)""" def visit_column(self,column): """Drop a column; #33""" table = self.start_alter_table(column) self.append(" DROP COLUMN %s"%column.name) self.execute() #if column.primary_key: # cons = self._pk_constraint(table,column,False) # cons.create() 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,param): """Rename a table; #38. Other ops aren't supported.""" table,newname = param self.start_alter_table(table) self.append("RENAME TO %s"%newname) self.execute() def visit_column(self,delta): """Rename/change a column; #34/#35""" # ALTER COLUMN is implemented as several ALTER statements 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 'primary_key' in keys: # #self._run_subvisit(delta,self._visit_column_primary_key) # self._visit_column_primary_key(delta) #if 'foreign_key' in keys: # self._visit_column_foreign_key(delta) if 'name' in keys: self._run_subvisit(delta,self._visit_column_name) def _run_subvisit(self,delta,func,col_name=None,table_name=None): if table_name is None: table_name = delta.table_name if col_name is None: col_name = delta.current_name ret = func(table_name,col_name,delta) self.execute() return ret 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_name,col_name,delta): nullable = delta['nullable'] table = self._to_table(delta) self.start_alter_table(table_name) self.append("ALTER COLUMN %s "%col_name) if nullable: self.append("DROP NOT NULL") else: self.append("SET NOT NULL") def _visit_column_default(self,table_name,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_name) self.append("ALTER COLUMN %s "%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_name,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.engine_impl(self.engine).get_col_spec() type_text = type.dialect_impl(self.dialect).get_col_spec() self.start_alter_table(table_name) self.append("ALTER COLUMN %s TYPE %s"%(col_name,type_text)) def _visit_column_name(self,table_name,col_name,delta): new_name = delta['name'] self.start_alter_table(table_name) self.append("RENAME COLUMN %s TO %s"%(col_name,new_name)) def visit_index(self,param): """Rename an index; #36""" index,newname = param #self.start_alter_table(index) #self.append("RENAME INDEX %s TO %s"%(index.name,newname)) self.append("ALTER INDEX %s RENAME TO %s"%(index.name,newname)) self.execute() 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): if cons.name is not None: ret = cons.name else: ret = cons.name = cons.autoname() return ret class ANSIConstraintGenerator(ANSIConstraintCommon): def get_constraint_specification(self,cons,**kwargs): if isinstance(cons,constraint.PrimaryKeyConstraint): col_names = ','.join([i.name for i in cons.columns]) ret = "PRIMARY KEY (%s)"%col_names if cons.name: # Named constraint ret = ("CONSTRAINT %s "%cons.name)+ret elif isinstance(cons,constraint.ForeignKeyConstraint): params = dict( columns=','.join([c.name for c in cons.columns]), reftable=cons.reftable, referenced=','.join([c.name for c in cons.referenced]), name=self.get_constraint_name(cons), ) ret = "CONSTRAINT %(name)s FOREIGN KEY (%(columns)s) "\ "REFERENCES %(reftable)s (%(referenced)s)"%params else: raise exceptions.InvalidConstraintError(cons) return ret def _visit_constraint(self,constraint): table = self.start_alter_table(constraint) self.append("ADD ") spec = self.get_constraint_specification(constraint) self.append(spec) self.execute() def visit_migrate_primary_key_constraint(self,*p,**k): return self._visit_constraint(*p,**k) def visit_migrate_foreign_key_constraint(self,*p,**k): return self._visit_constraint(*p,**k) class ANSIConstraintDropper(ANSIConstraintCommon): def _visit_constraint(self,constraint): self.start_alter_table(constraint) self.append("DROP CONSTRAINT ") self.append(self.get_constraint_name(constraint)) self.execute() def visit_migrate_primary_key_constraint(self,*p,**k): return self._visit_constraint(*p,**k) def visit_migrate_foreign_key_constraint(self,*p,**k): return self._visit_constraint(*p,**k) class ANSIDialect(object): columngenerator = ANSIColumnGenerator columndropper = ANSIColumnDropper schemachanger = ANSISchemaChanger @classmethod def visitor(self,name): return getattr(self,name) def reflectconstraints(self,connection,table_name): raise NotImplementedError()