Fabio Maulo talked about this en una de sus publicaciones de mapas por código.
Mapeo por ejemplo de código:
mapper.BeforeMapClass += (mi, type, map) =>
map.Id(idmap => idmap.Generator(Generators.HighLow,
gmap => gmap.Params(new
{
table = "NextHighValues",
column = "NextHigh",
max_lo = 100,
where = string.Format(
"EntityName = '{0}'", type.Name.ToLowerInvariant())
})));
Para FluentNHibernate, que podría hacer algo como:
public class PrimaryKeyConvention : IIdConvention
{
public void Apply(IIdentityInstance instance)
{
var type = instance.EntityType.Name;
instance.Column(type + "Id");
instance.GeneratedBy.HiLo(type, "NextHigh", "100",
x => x.AddParam("where", String.Format("EntityName = '{0}'", type));
}
}
Además, Fabio se explica cómo se puede utilizar para crear IAuxiliaryDatabaseObject
guión Hi-Lo.
private static IAuxiliaryDatabaseObject CreateHighLowScript(
IModelInspector inspector, IEnumerable<Type> entities)
{
var script = new StringBuilder(3072);
script.AppendLine("DELETE FROM NextHighValues;");
script.AppendLine(
"ALTER TABLE NextHighValues ADD EntityName VARCHAR(128) NOT NULL;");
script.AppendLine(
"CREATE NONCLUSTERED INDEX IdxNextHighValuesEntity ON NextHighValues "
+ "(EntityName ASC);");
script.AppendLine("GO");
foreach (var entity in entities.Where(x => inspector.IsRootEntity(x)))
{
script.AppendLine(string.Format(
"INSERT INTO [NextHighValues] (EntityName, NextHigh) VALUES ('{0}',1);",
entity.Name.ToLowerInvariant()));
}
return new SimpleAuxiliaryDatabaseObject(
script.ToString(), null, new HashedSet<string> {
typeof(MsSql2005Dialect).FullName, typeof(MsSql2008Dialect).FullName
});
}
Se podría utilizar de esta manera:
configuration.AddAuxiliaryDatabaseObject(CreateHighLowScript(
modelInspector, Assembly.GetExecutingAssembly().GetExportedTypes()));