-- This is script that creates identity triggers for all tables.
CREATE OR REPLACE FUNCTION GetOrganizationId() RETURNS bigint AS $$
    select CAST(value AS bigint) from public.setting set
    WHERE upper(set.name) = upper('org_id');
  $$ LANGUAGE SQL;

  CREATE OR REPLACE FUNCTION GetId(Id bigint) RETURNS bigint AS $$
    select Id * 1000 + GetOrganizationId() AS result;
  $$ LANGUAGE SQL;
  
  
  ----------------production_type:--------------------------------------
  CREATE SEQUENCE production_type_id_seq
  INCREMENT 1
  MINVALUE 1
  MAXVALUE 9223372036854775807
  START 1
  CACHE 1;
  
  CREATE OR REPLACE FUNCTION production_type_identity() RETURNS trigger AS $production_type_identity$
    BEGIN
    
        IF NEW.ID IS NULL THEN
            NEW.ID := GetId(nextval('production_type_id_seq'));
        END IF;
        RETURN NEW;
    END;
  $production_type_identity$ LANGUAGE plpgsql;

  CREATE TRIGGER production_type_identity BEFORE INSERT ON production_type
    FOR EACH ROW EXECUTE PROCEDURE production_type_identity();  
  ------------------------------------------------------

protected BaseMap()
        {
            Id(x => x.Id);
            Map(x => x.ObjectVersion, "OBJECT_VERSION").Not.Nullable();
......

Id(x => x.Id).GeneratedBy.TriggerIdentity();

Id(x => x.Id).GeneratedBy.Custom<NHibernate.Id.TriggerIdentityGenerator>();

INSERT INTO ROLE (
	OBJECT_VERSION,
	 OBJECT_CREATE_DATE,
	 OBJECT_EDIT_DATE,
	 CREATE_USER,
	 EDIT_USER,
	 NAME,
	 ACCESS_TO_CASHIER,
	 ACCESS_TO_ROLES)
 VALUES (
	0 /* :p0 */,
	 '2012-12-12T23:15:35.00' /* :p1 */,
	 '2012-12-12T23:15:35.00' /* :p2 */,
	 NULL /* :p3 */,
	 NULL /* :p4 */,
	 '1Супер кассир' /* :p5 */,
	 0 /* :p6 */,
	 'False [Type: Boolean (0)], :nhIdOutParam = NULL' /* :p7 */)
 returning Id

An AssertionFailure occurred - this may indicate a bug in NHibernate or in your custom types.

public class MyGenerator : IIdentifierGenerator
    {
        readonly Random _rnd1 = new Random();

        public object Generate(ISessionImplementor session, object obj)
        {
            return _rnd1.Next();
        }
    }

Id(x => x.Id).GeneratedBy.Custom<MyGenerator>();

Nhibernate.HibernateException: identifier of an instance of Canteen.Entities.Role was altered from 394866042 to 394866042

return Convert.ToInt64(_rnd1.Next());

select nextval('table_id_seq')

select nextval('table_id_seq')

<id type="long">
      <generator class="native">
          <param name="sequence">cust_id_seq</param>
      <param name="parameters">START WITH 10</param>
      </generator>
</id>

public class MyGenerator : IIdentifierGenerator
    {
        // TODO вынести из хард кода:
        private const int OrgId = 219;

        protected string TableName;

        public object Generate(ISessionImplementor session, object obj)
        {
            var connection = session.Connection;

            long seqNextValue = 0;

            ConnectionState originalState = connection.State;
            if (originalState != ConnectionState.Open)
                connection.Open();
            try
            {
                IDbCommand command = connection.CreateCommand();
                //TODO заполнять как-то TableName и строку сделать такой: "select nextval('{0}_id_seq')"
                command.CommandText = string.Format("select nextval('role_id_seq')", TableName);
                seqNextValue = (long)command.ExecuteScalar();
            }
            finally
            {
                // Close the connection if that's how we got it
                if (originalState == ConnectionState.Closed)
                    connection.Close();
            }
            return seqNextValue * 1000 + OrgId;
        }
    }

    public abstract class BaseMap<T> : ClassMap<T>
        where T : DataAccess.Entity.BaseEntity
    {
        protected string tableName;

        protected BaseMap()
        {
            Id(x => x.Id).GeneratedBy.Custom <MyGenerator>();
.....

/// <summary>
    /// NHibernate генератор ID
    /// </summary>
    public class MyGenerator : IIdentifierGenerator
    {
        /// <summary>
        /// Id орагнизации из БД
        /// </summary>
        private long _orgId;
        /// <summary>
        /// Следующее значение последовательности из БД
        /// </summary>
        private long _seqNextValue;

        /// <summary>
        /// Генерируем id для вставки записи в таблицу. 
        /// Запросы написаны для PostgreSQL. 
        /// Для другой СУБД нужно писать развилки.
        /// </summary>
        /// <param name="session"></param>
        /// <param name="obj"></param>
        /// <returns></returns>
        public object Generate(ISessionImplementor session, object obj)
        {
            var connection = session.Connection;

            ConnectionState originalState = connection.State;
            if (originalState != ConnectionState.Open)
                connection.Open();
            try
            {
                IDbCommand command = connection.CreateCommand();
                command.CommandText = string.Format("select nextval('HIBERNATE_SEQUENCE')");
                _seqNextValue = (long)command.ExecuteScalar();

                command.CommandText = string.Format("select CAST(value AS bigint) from setting set WHERE upper(set.name) = upper('org_id')");
                _orgId = (long)command.ExecuteScalar();
            }
            finally
            {
                // Close the connection if that's how we got it
                if (originalState == ConnectionState.Closed)
                    connection.Close();
            }
            return _seqNextValue * 1000 + _orgId;
        }
    }

    public abstract class BaseMap<T> : ClassMap<T>
        where T : DataAccess.Entity.BaseEntity
    {
        protected string TableName;

        protected BaseMap()
        {
            Id(x => x.Id).GeneratedBy.Custom<MyGenerator>();
......