nhibernatenhibernate-mapping

NHibernate ignores length attribute


After running SQL Profiler, I realized that NHibernate was mapping strings to nvarchar(4000). I fixed it by specifying type=AnsiString and length=... in the hbm file. It is now generating varchar(8000) statements, and it is ignoring the length. How come?

hbm file:

<property name="EmailAddress" column="EMAIL_ADDRESS" type="AnsiString" length="120" />

database field:

[EMAIL_ADDRESS] [varchar](120) NULL,

Solution

  • Actually in previous versions of nhibernate the check against length was implemented also for query creation.

    But, the current implementation of the SqlDriver got a change last year, see https://nhibernate.jira.com/browse/NH-3036 for details of the fix.

    Bugfix:

        // Used from SqlServerCeDriver as well
        public static void SetVariableLengthParameterSize(IDbDataParameter dbParam, SqlType sqlType)
        {
            SetDefaultParameterSize(dbParam, sqlType);
    
            // no longer override the defaults using data from SqlType, since LIKE expressions needs larger columns
            // https://nhibernate.jira.com/browse/NH-3036
            //if (sqlType.LengthDefined && !IsText(dbParam, sqlType) && !IsBlob(dbParam, sqlType))
            //{
            //  dbParam.Size = sqlType.Length;
            //}
    
            if (sqlType.PrecisionDefined)
            {
                dbParam.Precision = sqlType.Precision;
                dbParam.Scale = sqlType.Scale;
            }
        }
    

    The defaults are what you see (4000/8000) dependent on the data type...