diff options
Diffstat (limited to 'lib/sqlalchemy/dialects/oracle/base.py')
| -rw-r--r-- | lib/sqlalchemy/dialects/oracle/base.py | 61 |
1 files changed, 58 insertions, 3 deletions
diff --git a/lib/sqlalchemy/dialects/oracle/base.py b/lib/sqlalchemy/dialects/oracle/base.py index 7cb9aae57..2e5ce2581 100644 --- a/lib/sqlalchemy/dialects/oracle/base.py +++ b/lib/sqlalchemy/dialects/oracle/base.py @@ -18,10 +18,47 @@ Auto Increment Behavior SQLAlchemy Table objects which include integer primary keys are usually assumed to have "autoincrementing" behavior, meaning they can generate their -own primary key values upon INSERT. Since Oracle has no "autoincrement" +own primary key values upon INSERT. For use within Oracle, two options are +available, which are the use of IDENTITY columns (Oracle 12 and above only) +or the association of a SEQUENCE with the column. + +Specifying GENERATED AS IDENTITY (Oracle 12 and above) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Starting from version 12 Oracle can make use of identity columns using +the :class:`_sql.Identity` to specify the autoincrementing behavior:: + + t = Table('mytable', metadata, + Column('id', Integer, Identity(start=3), primary_key=True), + Column(...), ... + ) + +The CREATE TABLE for the above :class:`_schema.Table` object would be: + +.. sourcecode:: sql + + CREATE TABLE mytable ( + id INTEGER GENERATED BY DEFAULT AS IDENTITY (START WITH 3) NOT NULL, + ..., + PRIMARY KEY (id) + ) + +The :class:`_schema.Identity` object support many options to control the +"autoincrementing" behavior of the column, like the starting value, the +incrementing value, etc. +In addition to the standard options, Oracle supports setting +:paramref:`_schema.Identity.always` to ``None`` to use the default +generated mode, rendering GENERATED AS IDENTITY in the DDL. It also supports +setting :paramref:`_schema.Identity.on_null` to ``True`` to specify ON NULL +in conjunction with a 'BY DEFAULT' identity column. + +Using a SEQUENCE (all Oracle versions) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Older version of Oracle had no "autoincrement" feature, SQLAlchemy relies upon sequences to produce these values. With the -Oracle dialect, *a sequence must always be explicitly specified to enable -autoincrement*. This is divergent with the majority of documentation +older Oracle versions, *a sequence must always be explicitly specified to +enable autoincrement*. This is divergent with the majority of documentation examples which assume the usage of an autoincrement-capable database. To specify sequences, use the sqlalchemy.schema.Sequence object which is passed to a Column construct:: @@ -38,6 +75,10 @@ This step is also required when using table reflection, i.e. autoload=True:: autoload=True ) +.. versionchanged:: 1.4 Added :class:`_schema.Identity` construct + in a :class:`_schema.Column` to specify the option of an autoincrementing + column. + Transaction Isolation Level / Autocommit ---------------------------------------- @@ -1252,6 +1293,20 @@ class OracleDDLCompiler(compiler.DDLCompiler): text += " VIRTUAL" return text + def visit_identity_column(self, identity, **kw): + if identity.always is None: + kind = "" + else: + kind = "ALWAYS" if identity.always else "BY DEFAULT" + text = "GENERATED %s" % kind + if identity.on_null: + text += " ON NULL" + text += " AS IDENTITY" + options = self.get_identity_options(identity) + if options: + text += " (%s)" % options + return text + class OracleIdentifierPreparer(compiler.IdentifierPreparer): |