Incorrect Oracle create table generation if a table includes Guid

CreateTable<T> generates invalid CREATE TABLE statement if a table has a Guid column without an explicit DB type when Oracle provider is being used.

    [Table("Calculation")]
    public class Calculation
    {
        /// <summary>The Id</summary>
        [Column, Identity, PrimaryKey, NotNull]
        public int Id { get; set; }
        /// <summary>Client request id</summary>
        [Column, NotNull]
        public Guid RequestId { get; set; }
    }

Resulting sql:

CREATE TABLE pfe.Calculation
(
	Id           Int        NOT NULL,
	RequestId    Guid       NOT NULL,
	Status       Int        NOT NULL,
	PathCount    Int        NOT NULL,
	StartDate    timestamp  NOT NULL,
	TimeHorizon  Float      NOT NULL,
	FactorListId Int        NOT NULL,
	Created      timestamp  NOT NULL,
	Updated      timestamp  NOT NULL,

	CONSTRAINT PK_Calculation PRIMARY KEY (Id)
)

Oracle does not have the Guid column type. It should be raw(16). An addition of DataType = DataType.Binary, Length = 16 to the column attribute does not help also. After it the generated column type is Binary(16) which is also invalid. The only obvious way to workaround the problem is to set DbType=“Raw(16)” property of the Column attribute.

Environment details

linq2db version: 1.8.2
Database Server: Oracle 11g
Database Provider: Oracle.Managed
Operating system: Windows 7
Framework version: .NET Framework 4.6.2

[Lexey]

May be better to keep it and add proper default mappings later.

[ili]

About second issue this should help:

        [Column(DataType = DataType.VarBinary, Length = -1), NotNull]
        [Column(DataType = DataType.Blob, Configuration = DataProviderName.Oracle)]
        public byte[] Data { get; set; }