fixup! Support evaluation of Random.Next and NextDouble on db side

Fix random Oracle overflows.

Author: fredericDelaporte

src/NHibernate/Dialect/Oracle10gDialect.cs

@@ -23,7 +23,23 @@ protected override void RegisterFunctions()
 
 			// DBMS_RANDOM package was available in previous versions, but it was requiring initialization and
 			// was not having the value function.
-			RegisterFunction("random", new NoArgSQLFunction("DBMS_RANDOM.VALUE", NHibernateUtil.Double));
+			// It yields a decimal between 0 included and 1 excluded, with 38 significant digits. It sometimes
+			// causes an overflow when read by the Oracle provider as a .Net Decimal, so better explicitly cast
+			// it to double.
+			RegisterFunction("random", new SQLFunctionTemplate(NHibernateUtil.Double, "cast(DBMS_RANDOM.VALUE() as binary_double)"));
 		}
+
+		/* 6.0 TODO: consider redefining float and double registrations
+		protected override void RegisterNumericTypeMappings()
+		{
+			base.RegisterNumericTypeMappings();
+
+			// Use binary_float (available since 10g) instead of float. With Oracle, float is a decimal but
+			// with a precision expressed in number of bytes instead of digits.
+			RegisterColumnType(DbType.Single, "binary_float");
+			// Using binary_double (available since 10g) instead of double precision. With Oracle, double
+			// precision is a float(126), which is a decimal with a 126 bytes precision.
+			RegisterColumnType(DbType.Double, "binary_double");
+		}*/
 	}
 }