Submitted by: Juergen Thomas (juetho)

The result DataTable of the FbConnection.GetSchema("Columns") method sets the column "is_nullable" as follows:

If the database column itself is set to "not null" or if this column is part of the primary key, it returns is_nullable as correct value "1" resp. "true". If the database column is defined via domain and the domain is set to "not null", the column value "is_nullable" nevertheless returns incorrectly "1" resp. "true", but not the expected correct value "0" resp. "false".

Workaround: ..\source\FirebirdSql\Data\Schema\FbColumns.cs line 59
Use a clause like the following statement instead of line 59
(Sorry, I'm not fit with complex statements, you may find out a better one):

CASE
WHEN (rfr.rdb$field_source IS NULL) THEN rfr.rdb$null_flag
WHEN (rfr.rdb$field_source = '') THEN rfr.rdb$null_flag
WHEN (rfr.rdb$field_source STARTS With 'RDB$') THEN rfr.rdb$null_flag
WHEN (rfr.rdb$null_flag = '1') THEN rfr.rdb$null_flag
ELSE (SELECT flds.rdb$null_flag FROM rdb$fields flds WHERE rfr.rdb$field_source = flds.rdb$field_name)
END AS COLUMN_NULLABLE,

Test case:
create domain dom_int as int check(value > 0) not null
create domain dom_char as varchar(35)

create TABLE nullable_test (
id dom_int,
counter INT,
setting int not NULL,
content_1 Dom_char,
content_2 dom_char not null,
firstname varchar(35),
lastname varchar(35) not null
);
Columns 0, 2, 4, 6 must be "not null", 1, 3, 5 must "nullable".

Commits: 4588b3d cec562f