Synopse Open Source

In Delphi code, NULLable types do not exist as such. There is no native int? type, as in C#.
But at SQL and JSON levels, the NULL value does exist and should be converted as expected by the ORM.

In SQLite3 itself, NULL is handled as stated in http://www.sqlite.org/lang_expr.html (see e.g. IS and IS NOT operators).
It is worth noting that NULL handling is not consistent among all existing database engines, e.g. when you are comparing NULL with non NULL values... so we recommend using it with care in any database statements, or only with proper (unit) testing, when you switch from one database engine to another.

By default, in the mORMot ORM/SQL code, NULL will appear only in case of a BLOB storage with a size of 0 bytes.
Otherwise, you should not see it as a value, in most kinds of ORM properties.

Null-oriented value types have been implemented in our framework, since the object pascal language does not allow defining a nullable type (yet). 

We choose to store those values as variant, with a set of TNullable dedicated types, as defined in mORMot.pas:

type
  TNullableInteger = type variant;
  TNullableBoolean = type variant;
  TNullableFloat = type variant;
  TNullableCurrency = type variant;
  TNullableDateTime = type variant;
  TNullableTimeLog = type variant;
  TNullableUTF8Text = type variant;

Today, an avalanche of "false postitive detection" of AVAST heuristic engine did occur.
Any executable built with Delphi XE8 or Delphi 10 Seattle was identified as a Win32:Banker-MGC [Trj] threat!

Heuristic analysis is a method employed by many computer antivirus programs designed to detect previously unknown computer viruses, as well as new variants of viruses already in the "wild".

Back in 2013, I found out an implementation weakness in the implementation of ARC weak references in the RTL.
A giant lock was freezing all threads and cores, so would decrease a lot the performance abilities of any ARC application, especially in multi thread.

I just investigated that things are now better.