Working with NHibernate and Oracle Sequences? - sql

Question

How to work with NHibernate and Oracle using Oracle Sequence?
When I call to the SaveOrUpdate() method, it only performs a select query against the Oracle sequence.
I have used an interceptor to look up the query the session was performing, and the is the instruction I get:
select INFO_ACCESS_REQS_ID_SEQ.nextval from dual;
And that is the only thing being executed against the underlying Oracle database when I call to ISession.SaveOrUpdate().
hibernate.cfg.xml
<?xml version="1.0" encoding="utf-8"?>
<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2" >
<session-factory name="MyProject">
<property name="connection.driver_class">
NHibernate.Driver.OracleClientDriver
</property>
<property name="format_sql">true</property>
<property name="show_sql">true</property>
<property name="dialect">NHibernate.Dialect.Oracle10gDialect</property>
<property name="query.substitutions">
true 1, false 0, yes 'Y', no 'N'
</property>
</session-factory>
</hibernate-configuration>
InformationAccessRequest.hbm.xml
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
namespace="MyProject.Model"
assembly="MyProject">
<class name="InformationAccessRequest" table="INFO_ACCESS_REQS">
<id name="Id" column="INFO_ACCESS_REQS_ID">
<generator class="native">
<param name="sequence">INFO_ACCESS_REQS_ID_SEQ</param>
</generator>
</id>
<property name="Assembly" column="ASSEMBLY_DT" />
<property name="Requested" column="INFO_ACCESS_REQ_DT" />
<property name="Expiration" column="INFO_ACCESS_REQ_EXP_DT" />
<property name="RequesterIdentification" column="INFO_ACCESS_REQ_USR_ID" />
<property name="Number" column="INFO_ACCESS_REQ_NUM" />
<property name="Reception" column="INFO_ACCESS_REQ_RECEP_DT" />
<property name="Creator" column="CREATOR_ID" />
<property name="Created" column="CREATED_DT" />
<property name="Updater" column="UPDATER_ID" />
<property name="Updated" column="UPDATED_DT" />
<property name="Deleted" column="DELETED_DT" />
</class>
</hibernate-mapping>
ISession.SaveOrUpdate()
var newRequest = new InformationAccessRequest();
newRequest.Requested = DateTime.Today.AddDays(-1);
newRequest.Expiration = DateTime.Today.AddDays(1);
newRequest.Reception = DateTime.Today;
newRequest.Number = Guid.NewGuid().ToString().Substring(0, 12);
newRequest.RequesterIndentification = Guid.NewGuid()..ToString().Substring(0, 10);
newRequest.Created = DateTime.Today;
newRequest.Creator = User.Current.Login;
newRequest.IsNew = true;
newRequest.IsDirty = true;
session.SaveOrUpdate(newRequest);
All required information provided, and all database constraints respected. The SaveOrUpdate() only does the select against the sequence, and no other sql instruction gets performed.

Answer 1

I just discovered a new feature of NHibernate working with identity-type, though it is an old feature actually.
Based on this article: NH2.1.0: New generators, I shall specify the generator class as sequence-identity.
From that new generators article, here's the plain explanation:
sequence-identity
The “sequence-identity” is based on “sequence” but work as an “identity”. The POID values is retrieved with the INSERT query. The types, in your entity, maybe are System.Int32 or System.Int64 depending on your RDBMS sequence generator.
The query that run in ORACLE is:
INSERT INTO my_entity (id, name)
VALUES (hibernate_sequence.nextval, :p0) returning id into :nhIdOutParam
The “hibernate_sequence” is the default name for a sequence where no alternative name is provided trough the mapping. As you can see, in this case, the “sequence” are working like “identity”, the value of the POID is retrieved immediately and the generator has the same problem of “identity”.
InformationAccesRequest.hbm.xml (updated accordingly)
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
namespace="MyProject.Model"
assembly="MyProject">
<class name="InformationAccessRequest" table="INFO_ACCESS_REQS">
<id name="Id" column="INFO_ACCESS_REQS_ID">
<generator class="sequence-identity">
<param name="sequence">INFO_ACCESS_REQS_ID_SEQ</param>
</generator>
</id>
<property name="Assembly" column="ASSEMBLY_DT" />
<property name="Requested" column="INFO_ACCESS_REQ_DT" />
<property name="Expiration" column="INFO_ACCESS_REQ_EXP_DT" />
<property name="RequesterIdentification" column="INFO_ACCESS_REQ_USR_ID" />
<property name="Number" column="INFO_ACCESS_REQ_NUM" />
<property name="Reception" column="INFO_ACCESS_REQ_RECEP_DT" />
<property name="Creator" column="CREATOR_ID" />
<property name="Created" column="CREATED_DT" />
<property name="Updater" column="UPDATER_ID" />
<property name="Updated" column="UPDATED_DT" />
<property name="Deleted" column="DELETED_DT" />
</class>
</hibernate-mapping>