new to NHibernate (and Hibernate for that matter), and I'm struggling with a composite key problem. Here's a simplified version of part of the database design.
table_a
+---------------------+
| * a_id varcha (10) | table_z
| label varchar(50) | +----------------------+
| +<----------------+ * a_id varchar(10) |
+---------------------+ +----------| * b_id varchar(10) |
| +------+ * c_id varchar(10) |
table_b | | | name varchar(100) |
+---------------------+ | | | |
| * b_id varcha (10) | | | +----------------------+
| label varchar(50) <------+ |
| | |
+---------------------+ |
|
table_c |
+---------------------+ |
| * c_id varcha (10) <----------+
| label varchar(50) |
| |
+---------------------+
The key element here is table_z primary key is a composite of the 3 primary keys of table a,b,c (so, it controls unique combinations of a,b and c). They are also individually FK to table_a, table_b and table_c.
Now, beyond database design considerations, is there a way to map this into NHibernate. My attemps result in a stack trace complaining that "ArgumentException: The column 'a_id' has already been added in this SQL builder". Googling around told me that the issue is that I use the same field name on both end of the join. I'm surprised it's even an issue - or I totally misunderstand the problem..
Here's the DDL (Postgresql)
CREATE TABLE test.table_a(
a_id varchar(10) primary key,
label varchar(50)
);
CREATE TABLE test.table_b(
b_id varchar(10) primary key,
label varchar(50)
);
CREATE TABLE test.table_c(
c_id varchar(10) primary key,
label varchar(50)
);
CREATE TABLE test.table_z(
a_id varchar(10),
b_id varchar(10),
c_id varchar(10),
name varchar(100)
);
-- add combined primary key on table_z
ALTER TABLE test.table_z ADD CONSTRAINT pk_z_combined
PRIMARY KEY (a_id,b_id,c_id)
;
-- FK
ALTER TABLE test.table_z ADD CONSTRAINT FK_to_a
FOREIGN KEY (a_id) REFERENCES test.table_a (a_id) ON DELETE No Action ON UPDATE No Action;
ALTER TABLE test.table_z ADD CONSTRAINT FK_to_b
FOREIGN KEY (b_id) REFERENCES test.table_b (b_id) ON DELETE No Action ON UPDATE No Action;
ALTER TABLE test.table_z ADD CONSTRAINT FK_to_c
FOREIGN KEY (c_id) REFERENCES test.table_c (c_id) ON DELETE No Action ON UPDATE No Action;
and here's the Fluent Hibernate C# code
using FluentNHibernate.Mapping;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace pm
{
class TestAMapping : ClassMap<TestA>
{
public TestAMapping()
{
Table("test.table_a");
Id(x => x.Id, "a_id");
Map(x => x.Label, "label");
}
}
class TestBMapping : ClassMap<TestB>
{
public TestBMapping()
{
Table("test.table_b");
Id(x => x.Id, "b_id");
Map(x => x.Label, "label");
}
}
class TestCMapping : ClassMap<TestC>
{
public TestCMapping()
{
Table("test.table_c");
Id(x => x.Id, "c_id");
Map(x => x.Label, "label");
}
}
class TestZMapping : ClassMap<TestZ>
{
public TestZMapping()
{
Table("test.table_z");
CompositeId()
.KeyProperty(x => x.Aid, "a_id")
.KeyProperty(x => x.Bid, "b_id")
.KeyProperty(x => x.Cid, "c_id");
Map(x => x.Name, "name");
References(x => x.TestAObj).Column("a_id");
References(x => x.TestBObj).Column("b_id");
References(x => x.TestCObj).Column("c_id");
}
}
class TestA
{
public virtual string Id { get; set; }
public virtual string Label { get; set; }
}
class TestB
{
public virtual string Id { get; set; }
public virtual string Label { get; set; }
}
class TestC
{
public virtual string Id { get; set; }
public virtual string Label { get; set; }
}
class TestZ
{
public virtual string Aid { get; set; }
public virtual string Bid { get; set; }
public virtual string Cid { get; set; }
public virtual string Name { get; set; }
public virtual TestA TestAObj { get; set; }
public virtual TestB TestBObj { get; set; }
public virtual TestC TestCObj { get; set; }
// https://stackoverflow.com/a/7919012/8691687
public override bool Equals(object obj)
{
var other = obj as TestZ;
if (ReferenceEquals(null, other)) return false;
if (ReferenceEquals(this, other)) return true;
return this.Aid == other.Aid &&
this.Bid == other.Bid && this.Cid == other.Cid;
}
public override int GetHashCode()
{
unchecked
{
int hash = GetType().GetHashCode();
hash = (hash * 31) ^ Aid.GetHashCode();
hash = (hash * 31) ^ Bid.GetHashCode();
hash = (hash * 31) ^ Cid.GetHashCode();
return hash;
}
}
}
}
Relevant stack trace
FluentNHibernate.Cfg.FluentConfigurationException
HResult=0x80131500
Message=An invalid or incomplete configuration was used while creating a SessionFactory. Check PotentialReasons collection, and InnerException for more detail.
Source=FluentNHibernate
StackTrace:
at FluentNHibernate.Cfg.FluentConfiguration.BuildSessionFactory()
at pm.dal.DAL.CreateSessionFactory(String connectionString) in C:\Users\Laptop\source\repos\pm\dal\DAL.cs:line 49
at pm.dal.DAL..ctor(String connectionString) in C:\Users\Laptop\source\repos\pm\dal\DAL.cs:line 41
at pm.Manager.Manager.Connect(String connectionString) in C:\Users\Laptop\source\repos\pm\Manager\Manager.cs:line 102
(blah...)
Inner Exception 1:
MappingException: Unable to build the insert statement for class pm.TestZ: a failure occured when adding the Id of the class
Inner Exception 2:
ArgumentException: The column 'a_id' has already been added in this SQL builder
Parameter name: columnName
Can anyone tell me where I sinned..
Thanks a heap
I just looked how I did it in my project. Unfortunately I cannot describe why this is the way to go ;-)
public TestZMapping()
{
Table("test.table_z");
CompositeId()
.KeyProperty(x => x.Aid, "a_id")
.KeyProperty(x => x.Bid, "b_id")
.KeyProperty(x => x.Cid, "c_id");
Map(x => x.Name, "name");
References(x => x.TestAObj).Column("a_id").Not.Insert().Not.Update();
References(x => x.TestBObj).Column("b_id").Not.Insert().Not.Update();
References(x => x.TestCObj).Column("c_id").Not.Insert().Not.Update();
}