HiLo NHibernate id generator implementation - nhibernate

I would like to use "hilo" generator but there is no any complete example how to create "specific" table as NH documentation says, and which values pass to it.
The following code fragments taken from NH tutorial
public class Cat
{
private Int64 id;
private string name;
private char sex;
private float weight;
public Cat()
{}
public virtual Int64 Id
{
get { return id; }
set { id = value; }
}
....
}
Mapper
<hibernate-mapping ...>
<class name="Cat" table="Cat">
<id name="Id" >
<column name="CatId" sql-type="Int64" not-null="true"/>
<generator class="hilo"/>
</id>
<property name="Name">
<column name="Name" length="16" not-null="true" />
</property>
....
</class>
</hibernate-mapping>
DB table "Cat"
CatId bigint NOT NULL
Name varchar(16) NOT NULL
Sex char(1) NULL
Weight real NULL
doesn't create anything in the database by default.
Parameters in the "id" node
<param name="table">hi_value</param>
<param name="column">next_value</param>
<param name="max_lo">100</param>
gives "Invalid object name 'hi_value'" error message, without them I'm getting "Invalid object name 'hibernate_unique_key'."
Cuid.Comb that is shown in their tutorial works good but gives 99.12% of fragmentation when I added in a loop 20K cat objects.
Can somebody point me to an example of "hilo" implementation or give a tip what I'm missing?
Thanks.

This solution solved my problem. It's fairly simple, don't know why on nhibernate site there is no tiny example like that.

You may be running into NH-2687.

Related

HQL Query SELECT with NOT IN

I need a HQL Query but I just dont get it.
SELECT * FROM Poll WHERE pid NOT IN (
SELECT pid FROM votes WHERE uid = 'theuserid')
I want all List of PollĀ“s back where the uid not in the table votes exists.
Also helpfull would be the hql query where the uid in the table votes exists, but I guess this is very similar ;-)
These are the 2 classes:
public class Poll {
private int pid;
private String name;
private String description;
private Date deadline;
private Set<Team> teams = new HashSet<Team>(0);
//some getter & setter
}
public class Vote {
private int vid;
private String uid;
private int pid;
private int tid;
private int votes;
//some getter & setter
}
Can smbdy please help me. I guess it is a join with a WHERE and NOT LIKE but I just dont get it.
Merci!
This is btw the hibernate mapping:
<hibernate-mapping>
<class name="package.model.Poll" table="poll">
<id name="pid" column="pid" >
<generator class="increment"/>
</id>
<property name="name" column="name" />
<property name="description" column="description" />
<property name="deadline" type="timestamp" column="deadline" />
<set name="teams" table="pollchoice"
inverse="false" lazy="false" fetch="select" cascade="all" >
<key>
<column name="pid" not-null="true" />
</key>
<many-to-many entity-name="knt.exceedvote.model.Team">
<column name="tid" not-null="true" />
</many-to-many>
</set>
</class>
</hibernate-mapping>
<hibernate-mapping>
<class name="package.model.Vote" table="votes">
<id name="vid" column="vid" >
<generator class="increment"/>
</id>
<property name="pid" column="pid" />
<property name="uid" column="uid" />
<property name="tid" column="tid" />
<property name="votes" column="votes" />
</class>
</hibernate-mapping>
Please keep in mind, Hibernate is designed using the notion of Object Graph, which is a name given to the relational objects.
That core concept is missing in your mapping (Poll and Vote seem to be isolated) hence I doubt you can use HQL in its current state.
In my opinion, you have two options:
Define the relationship between Poll, pid and Vote, uid. Then you should be able to write simple HQL.
Use native SQL through Hibernate session itself.

nHibernate named query, result transformation and column name with whitespace

I've got a named nHibernate query which returns custom data. So I decided to make a bean class to encapsulate data. Here is some code:
public IList<Report> GetReport(int reportId)
{
return Session.GetNamedQuery("GetReport")
.SetParameter("Id", reportId)
.List<Report>();
}
public class Report
{
public virtual string Id { get; set; }
...
public virtual string CustomColumn { get; set; }
}
and mapping:
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="MyAssembly"
namespace="MyAssembly.Model">
<class name="Report" table="Report">
<id name="Id" column="Id">
<generator class="assigned"/>
</id>
...
<property column="`Custom column`" name="CustomColumn" />
</class>
<sql-query name="GetReport">
<return class="Report"/>
<query-param name="Id" type="int" />
exec GetReport :Id
</sql-query>
</hibernate-mapping>
But when I invoke this method I got an exception:
NHibernate.Exceptions.GenericADOException : could not execute query
----> System.IndexOutOfRangeException : [Custom column]
Help, anyone?
Ok, I found the problem myself. I thought, that I need to escape column names which contains spaces with ` as I do for table names. But apparently I shouldn't.
This syntax is fine.
<property column="Custom column" name="CustomColumn" />

Querying a many-to-many collection or how to include a many-to-many table in a criteria query?

I am quite new to the world of NHibernate and I can't seem to get this to work with the use of a criteria query: query a many-to-many relationship or query a collection (set/bag) on an entity. I've searched the internet and checked all the NHibernate books we have, but I can't find a specific answer to my "challenge".
I have made a simplified example of the problem I'm trying to solve. I have a table with books, a table with categories and a many-to-many table with the categories per book. Here are some of the technicalities:
data structure:
create table tableBook
(
BkId integer not null default autoincrement,
BkTitle char(40) not null,
BkWriter char(40) not null,
primary key (BkId)
);
create table tableCategory
(
CatId integer not null default autoincrement,
CatCode char(3) not null,
CatDesc char(40),
primary key (CatId)
);
create table tableCategoriesPerBook
(
CpbId integer not null default autoincrement,
CpbBkId integer not null, /*foreign key to tableBook*/
CpbCatId integer not null, /*foreign key to tableCategory*/
primary key (CpbId)
);
alter table tableCategoriesPerBook add foreign key FK_CpbBkId (CpbBkId) references tableBook (BkId) on update Restrict on delete Cascade;
alter table tableCategoriesPerBook add foreign key FK_CpbCatId (CpbCatId) references tableCategory (CatId) on update Restrict on delete Cascade;
create unique index idx_CpbCatId_CpbBkId on tableCategoriesPerBook (CpbCatId, CpbBkId);
C# classes:
public class BookEntity
{
public virtual Int32 BookId { get; set; }
public virtual string BookTitle { get; set; }
public virtual string BookWriter { get; set; }
private readonly IEnumerable<CategoryEntity> _categories = new ObservableCollection<CategoryEntity>();
public virtual IEnumerable<CategoryEntity> Categories
{
get { return _categories; }
}
}
public class CategoryEntity
{
public virtual Int32 CategoryId { get; set; }
public virtual string CategoryCode { get; set; }
public virtual string CategoryDesc { get; set; }
}
NHibernate mappings:
<?xml version="1.0" encoding="utf-8"?>
<hibernate-mapping namespace="Domain" assembly="Domain" xmlns="urn:nhibernate-mapping-2.2">
<class name="Domain.BookEntity" table="tableBook">
<id name="BookId" column="BkId" type="Int32">
<generator class="native" />
</id>
<property name="BookTitle" column="BkTitle" type="string" length="40"/>
<property name="BookWriter" column="BkWriter" type="string" length="40"/>
<idbag name="_categories" access="field" table="tableCategoriesPerBook">
<collection-id type="Int32" column="CpbId">
<generator class="native"/>
</collection-id>
<key column="CpbBkId" property-ref="BkId"/>
<many-to-many column="CpbCatId" class="Domain.CategoryEntity, Domain" />
</idbag>
</class>
</hibernate-mapping>
<?xml version="1.0" encoding="utf-8"?>
<hibernate-mapping namespace="Domain" assembly="Domain" xmlns="urn:nhibernate-mapping-2.2">
<class name="Domain.CategoryEntity" table="tableCategory">
<id name="CategoryId" column="CatId" type="Int32">
<generator class="native" />
</id>
<property name="CategoryCode" column="CatCode" type="string" length="3" />
<property name="CategoryDesc" column="CatDesc" type="string" length="40" />
</class>
</hibernate-mapping>
My question: is it possible to query (using ICriteria and/or detached criterias) the database in such a way that I get the books which is in one of the categories I specify (for instance: in catA or catB, could be "and" as well)? I want to optimize this in the query, not in C# (as I need to read all books from the database before I can filter the objects based on their collection of tags). If I'd write the SQL by hand, I would produce something like this:
SELECT * FROM tableBook
WHERE EXISTS
(
SELECT 1
FROM tableCategoriesPerBook
INNER JOIN tableCategory on (CpbCatId = CatId and CpbBkId = BkId)
WHERE CatCode in ('001', '002')
)
Since I don't have an entity for tableCategoriesPerBook, I don't see a way to get to this table with a criteria query. And I'd rather not add some handwritten piece of SQL expressions using:
criteria.Add(Expression.Sql("exists(.....)");
One last important factor: I am using a brownfield database, so I can't change the structure! this is what I'll have to work with database-wise.
This is pretty straight forward. You can use a detached criteria.
DetachedCriteria bookCategoryCriteria = DetachedCriteria.For<BookEntity>("bookCat");
bookCategoryCriteria
.CreateAlias("Categories", "cat", JointType.LeftOuterJoin)
.Add(Restrictions.In("cat.CategoryCode", categories)
.Add(Restrictions.Eq("bookCat.BookId", "book.BookId")
.SetProjection(Projections.Id());
Session.CreateCriteria<BookEntity>("book")
.Add(Subqueries.Exists(bookCategoryCriteria));

NHibernate filter collection

Using NHibernate I want to filter a collection in a class to contain ONLY a subset of possible objects. Below I am including a sample table data to help explain. I can find no way to do this using NHibernate.
Table:DataObject
DataObjectId(PK) / Name / CurrentVersion
11 "data.txt" 2
12 "info.txt" 3
Table:DataObjectVersion
Id / Comment / VersionNumber / DataObjectId(FK)
31 "Genesis" 1 11 <= Ignore this object
32 "Changed data" 2 11 <= Get this object
34 "Genesis" 1 12 <= Ignore this object
35 "Changed info" 2 12 <= Ignore this object
36 "Added info" 3 12 <= Get this object
I want to join on a non-foreign key DataObject.CurrentVersion = DataObjectVersion.VersionNumber for each DataObject in one command.
Here are the classes and mapping files:
public class DataObject
{
public virtual int DataObjectId { get; set; }
public virtual string Name { get; set; }
public virtual int CurrentVersionNumber { get; set; }
public virtual IList<DataObjectVersion> Versions { get; set; }
}
<class name="DataObject" table="DataObject" lazy="false">
<id name="DataObjectId" column="DataObjectId" type="int">
<generator class="assigned" />
</id>
<property name="Name" column="Name" type="String(512)" />
<property name="CurrentVersionNumber" column="CurrentVersionNumber" type="int" />
<bag name="Versions" cascade="all-delete-orphan" inverse="true" lazy="false" >
<key column="DataObjectId" />
<one-to-many class="DataObjectVersion" />
</bag>
</class>
public class DataObjectVersion
{
public virtual int DataObjectVersionId { get; set; }
public virtual string Comment { get; set; }
public virtual int VersionNumber { get; set; }
public virtual int DataObjectId { get; set; }
}
<class name="DataObjectVersion" table="DataObjectVersion" lazy="false">
<id name="Id" column="DataObjectVersionId" type="int">
<generator class="assigned" />
</id>
<property name="Comment" column="Comment" type="String(512)" />
<property name="VersionNumber" column="VersionNumber" type="int" />
<property name="DataObjectId" column="DataObjectId" type="int" />
</class>
if you want to filter the collection on demand, using a filter is a valid choice.
You would need to declare the filter on both the Version class and in the bag element and apply the filter from the NHibernateSession.EnableFilter method
if you always want to fetch a single Version in the bag then implement a 'where' in the mapping of the bag:
<bag name="Versions" cascade="all-delete-orphan" inverse="true" lazy="false" where="CurrentVersionNumber = Versions.VersionNumber" >
<key column="DataObjectId" />
<one-to-many class="DataObjectVersion" />
</bag>
note that in the 'where' you write proper SQL not HQL and as such the proper SQL i write above probably has to be changed to reflect your schema
Additionally if a single object is to be fetched setting up a bag and the according IList may be an overkill.
Applying a formula property and a DataObjectVersion object in the class may be more appropriate
in the class DataObject replace the IList with
public virtual DataObjectVersion Version { get; set; }
and in the mapping replace the 'bag' with something in the lines of
<property name="Version" type="DataObjectVersion" update="false" insert="false" formula="(select v.DataObjectVersionId, v.Comments, v.VersionNumber, v.DataObjectId from DataObjectVersion v where v.VersionNumber = CurrentVersionNumber)" />
again only proper SQL is allowed
i've used computed properties with native datatypes (datetime, string etc) and fetching an Entity may (or may not) need something more or different
Last but not least, you could apply a filter on the collection after you have fetched the primary object DataObject by creating a filter on the collection
IList<DataObjectVersion> fVersion =
NHibernateSession.CreateFilter(do.Versions, "where VersionNumber = :ver")
.SetParameter("ver", do.CurrentVersionNumber)
.List<DataObjectVersion>();
where the do.Versions collection is not initialized, only the results fetched in the separate fVersion collection and this is a second SELECT after already having made the round-trip to the db for the DataObject fetch.
Presumably your VersionNumber increments as the user changes the data and you're trying to get the latest one. If you consider the VersionNumber as an "Age" field instead (i.e. where 0 is the latest / youngest version, 1 is the next oldest and so on) then your problems becomes how to get all the entities with an Age of 0. This can be done using a filter: http://nhibernate.info/doc/nh/en/index.html#objectstate-filters

NHibernate bidirectional many-to-many association

I have a class with following description:
public class Customer {
public ISet<Client> Contacts { get; protected set;}
}
I want to map Contacts property onto following table:
CREATE TABLE user_contacts (
user1 uuid NOT NULL,
user2 uuid NOT NULL
)
I want it to map bidirectionally, i.e. when Customer1 added to Customer2's Contacts, Customer1's Contacts collection should contain Customer2 (maybe only after entity reload). How could I do that?
Update Sure I can map left-to-right and right-to-left sets and then combine then at runtime, but it'll... hmm... untasty... Is there other solution? Any way, thank you very match, FryHard!
Take a look at this link on what hibernate calls unidirectional many-to-many associations. In Castle ActiveRecord I make use of HasAndBelongsToMany links, but I am not sure how exactly it is mapped in nhibernate.
Though taking a look at your question a little deeper, it looks like you will be linking bidirectionally from customer to user_contacts, which could break the many-many link. I will play with an example and see what I can come up with.
An Export of the hbm files from ActiveRecord shows this
<?xml version="1.0" encoding="utf-16"?>
<hibernate-mapping auto-import="true" default-lazy="false" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="urn:nhibernate-mapping-2.2">
<class name="NHibernateMapping.Customer, NHibernateMapping" table="Customer" schema="dbo">
<id name="Id" access="property" column="Id" type="Int32" unsaved-value="0">
<generator class="identity">
</generator>
</id>
<property name="LastName" access="property" type="String">
<column name="LastName" not-null="true"/>
</property>
<bag name="ChildContacts" access="property" table="user_contacts" lazy="false">
<key column="user1" />
<many-to-many class="NHibernateMapping.Customer, NHibernateMapping" column="user2"/>
</bag>
<bag name="ParentContacts" access="property" table="user_contacts" lazy="false" inverse="true">
<key column="user2" />
<many-to-many class="NHibernateMapping.Customer, NHibernateMapping" column="user1"/>
</bag>
</class>
</hibernate-mapping>
ActiveRecord example:
[ActiveRecord("Customer", Schema = "dbo")]
public class Customer
{
[PrimaryKey(PrimaryKeyType.Identity, "Id", ColumnType = "Int32")]
public virtual int Id { get; set; }
[Property("LastName", ColumnType = "String", NotNull = true)]
public virtual string LastName { get; set; }
[HasAndBelongsToMany(typeof(Customer), Table = "user_contacts", ColumnKey = "user1", ColumnRef = "user2")]
public IList<Customer> ChildContacts { get; set; }
[HasAndBelongsToMany(typeof(Customer), Table = "user_contacts", ColumnKey = "user2", ColumnRef = "user1", Inverse = true)]
public IList<Customer> ParentContacts { get; set; }
}
Hope it helps!