How to extend NHibernate to support more databases?

If I need NHibernate to support more databases (not on the supported list: https://www.hibernate.org/361.html ), assuming the database can be accessed using the built-in query language, but not SQL ( e.g.: http://kx.com/Products/kdb+.php ) ...

  • How can I get NHibernate to work with these databases?
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1 answer

NHibernate is designed to work with SQL dialects, not special query languages. It will be very difficult to do. But to answer your question you need:

  • ADO.NET ( ).
  • ( NHibernate DriverBase). , ( ):

    public sealed class XxxClientDriver : DriverBase
    {
        public override IDbConnection CreateConnection()
        {
            return XxxClientFactory.Instance.CreateConnection();
        }
        public override IDbCommand CreateCommand()
        {
            return XxxClientFactory.Instance.CreateCommand();
        }
        public override bool UseNamedPrefixInSql
        {
            get { return true; }
        }
        public override bool UseNamedPrefixInParameter
        {
            get { return true; }
        }
        public override string NamedPrefix
        {
            get { return "@"; }
        }
    }
    
  • ( ) Dialect, NHibernate Dialect, ( , , SQL, , ). :

    public sealed class XxxDialect : Dialect
    {
        public override JoinFragment CreateOuterJoinFragment()
        {
            return new XxxJoinFragment();
        }
    }
    
  • ( SQL). , :

    public sealed class XxxJoinFragment : JoinFragment
    {
        private readonly SqlStringBuilder _afterFrom;
        public XxxJoinFragment()
        {
            _afterFrom = new SqlStringBuilder();
        }
        private SqlStringBuilder AfterFrom
        {
            get { return _afterFrom; }
        }
        public override SqlString ToFromFragmentString
        {
            get { return _afterFrom.ToSqlString(); }
        }
        public override SqlString ToWhereFragmentString
        {
            get { return SqlString.Empty; }
        }
        public override void AddJoin(string tableName, string alias,
            string[] fkColumns, string[] pkColumns,
            JoinType joinType)
        {
            AddCrossJoin(tableName, alias);
        }
        public override void AddJoin(string tableName, string alias,
            string[] fkColumns, string[] pkColumns,
            JoinType joinType, string on)
        {
            AddJoin(tableName, alias, fkColumns, pkColumns, joinType);
        }
        public override void AddCrossJoin(string tableName, string alias)
        {
            AfterFrom.Add(", ").Add(tableName).Add(" ").Add(alias);
        }
        public override void AddJoins(SqlString fromFragment, SqlString whereFragment)
        {
            AddFromFragmentString(fromFragment);
        }
        public override bool AddCondition(string condition)
        {
            return true;
        }
        public override bool AddCondition(SqlString condition)
        {
            return true;
        }
        public override void AddFromFragmentString(SqlString fromFragmentString)
        {
            AfterFrom.Add(fromFragmentString);
        }
    }
    

, (SQL- ) . , . !

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Source: https://habr.com/ru/post/1712293/


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