orm2.adapters.firebird.datatypes

59 """ 60 Datatype for automatically gernerated ids. 61 62 From U{The FireBird FAQ <http://firebird.sourceforge.net/index.php?op=faq#q0011.dat>} 63 64 How can i make an auto-incrementing primary key column? and is the NOT NULL constraint mandatory for a primary key? 65 =================================================================================================================== 66 In Firebird, you achieve an auto-incrementing PK using a generator 67 and a BEFORE INSERT trigger:: 68 69 CREATE GENERATOR GEN_PK_ATABLE; 70 COMMIT; 71 72 Define the column, e.g., ATABLE_ID, as BIGINT or INTEGER and yes, 73 the NOT NULL constraint is mandatory for a primary key. 74 75 The trigger for automatic population of the key is this:: 76 77 CREATE TRIGGER BI_ATABLE FOR ATABLE 78 ACTIVE BEFORE INSERT 79 AS 80 BEGIN 81 IF(NEW.ATABLE_ID IS NULL) THEN 82 NEW.ATABLE_ID = GEN_ID(GEN_PK_ATABLE, 1); 83 END 84 85 I{This is B{NOT} what orm does! It does...} 86 87 How can I get the value of my generated primary key after an insert ? 88 ===================================================================== 89 Firebird doesn't currently return values from insert statements 90 and, in multi-user, it isn't safe to query the generator 91 afterwards (GEN_ID(Generator_name, 0) because you have no way 92 to know whether the current 'latest' value was yours or someone 93 else's. The trick is to get the generator value into your 94 application as a variable before you post your insert. This 95 way, you make it available not just for your insert but for any 96 dependent rows you need to create for it inside the same 97 transaction:: 98 99 SELECT GEN_ID(Generator_name, 1) AS MyVar FROM RDB$DATABASE; 100 101 Some data access interfaces and drivers provide ways to do this 102 automatically for you. For example, IB Objects implements the 103 GeneratorLinks property for statement classes. 104 105 106 How it is handeld by orm 107 ======================== 108 orm is the kind of interface that does this automatically for 109 you. For any serial (and in fact L{common_serial 110 <orm2.datatypes.common_serial>}, see above) column it will query 111 the corresponding sequence and store the resulting value in the 112 right attribute to be used in the INSERT statement. If you use 113 a serial as your primary key, the select_after_insert() 114 mechanism (see L{orm2.datasource.datasource}) will work 115 correctly. 116 117 """ 118

119 - def __init__(self, column=None, sequence=None, title=None, 120 validators=(), widget_specs=()):

121 """ 122 @param sequence: Either a string or a sql.identifyer instance, 123 naming the sequence to be used by this serial column. Defaults 124 to GEN_PK_<relation name> 125 """ 126 integer.__init__(self, column, title, validators, widget_specs, 127 has_default=True) 128 129 self.sequence = sequence

130

131 - def __init_dbclass__(self, dbclass, attribute_name):

132 integer.__init_dbclass__(self, dbclass, attribute_name) 133 134 if self.sequence is None: 135 self.sequence = "GEN_PK_%s" % upper(dbclass.__relation__.name) 136 137 if type(self.sequence) == StringType: 138 self.sequence = sql.identifyer(self.sequence)

139

140 - def __set__(self, dbobj, value):

141 if self.isset(dbobj): 142 raise ORMException( "A auto_increment property is not mutable, "+\ 143 "once it is on object creation" ) 144 else: 145 integer.__set__(self, dbobj, value)

Source Code for Module orm2.adapters.firebird.datatypes