Hi Christian, It took me a while to have a closer look at your suggested solution, but I finally had some time for it.
I do have a few/questions remarks. Maybe some it is caused by using different versions of OJB, I do not know... We use 1.0rc5, but all the things you describe, match this version as far as I can tell. As I understand your example, it boils down to the appendParameter method in your solution. That method adds the String representation of the value into the query instead of the questionmark, used as argument placeholder in the prepared statement. In your example you use the asDBParameter method, but that one is not available within 1.0rc5 version of OJB. However, it seems unlikely to me that this method will do everything that is required. This method has just one argument, a value represented by an instance of a java datatype (integer/date/string/...). What the asDBParameter should do is the following: 1. execute the fieldconversion for the attribute associated with this value, which is given by the fielddescriptor 2. convert the outcome of the fieldconversion into a JDBC typed object instance 3. add the string value representation of the result from step 2 to into the query For step one you require the classdescriptor and the fieldname, or the fielddescriptor. The method asDBParameter does not have access to these objects! They are not passed as arguments. Neither does the encapsulating appendParameter method. So to make this work, these arguments should be passed on, with all these nested method calls, which implies that you have to change a lot of existing OJB method signatures (api interfaces). I am reluctant to do so, because this would really complicate migrating to newer versions of OJB. Step two is not obvious as well. The current OJB solution embeds this conversion inside the PreparedStatement class (used in the StatementManager en Platform-implementation classes), it's like a black box, and you cannot pull the converted argument values out of this statement. So I have no solution yet to perform the conversion. So how are the fieldconversions executed in your suggested solution, and when does the java to jdbc datatype conversion takes place? What also is missing in your solution is that in the end, the StatementManager class (in 1.0rc5) binds all the values to the parameters. This now should no longer be necessary, so you need to implement your own JdbcAccessImpl class that implements a custom public ResultSetAndStatement executeQuery(Query query, ClassDescriptor cld) throws PersistenceBrokerException method. Within this method, the value/parameter binding can be removed (call to method of StatementManager). Not doing this, may not lead to errors, but doing this will remove a lot of now redundant overhead. So... a bit late... but here is my response on your suggested solution and the exaample code you send. Of course... there is always a chance that I got it completely wrong, please let me know. Greetings, Roger Janssen iBanx -----Original Message----- From: Christian Lipp [mailto:[EMAIL PROTECTED] Sent: Wednesday, March 05, 2008 5:45 PM To: 'OJB Users List' Subject: RE: Is it possible to force OJB not use execute a prepared statement? In the OJB property file you have an entry "SqlGeneratorClass", which allows you to choose a different generator implementation. Override SqlGeneratorDefaultImpl. You have to implement a ctor, which calls the super ctor and a function getPreparedSelectStatement(), which delegates to your own Statement class. This means that you handle SELECT statements, the rest (INSERT, DELETE, UPDATE) is still handeld by SqlGeneratorDefaultImpl. If you want more, you have to override getPreparedDeleteStatement for DELETE and so on. The class would look like: Then you have to write your own statement class (override SqlSelectStatement). Again, you have to implement the ctors and override the function appendParameter(). In this function you have to format the concrete value (function asDBParameter): /** * Overridden method; appends the Parameter (real value) or the sub-query. * @param value the value of the criteria */ protected void appendParameter(Object value, StringBuffer buf) { if (value instanceof Query) { super.appendSubQuery((Query) value, buf); } else { buf.append(asDBParameter(value)); } } Since the statements are recursive, you also have to override getSubQuerySQL: /** * Convert subQuery to SQL * @param subQuery the subQuery value of SelectionCriteria */ protected String getSubQuerySQL(Query subQuery) { ClassDescriptor cld = getRoot().cld.getRepository().getDescriptorFor(subQuery.getSearchClass()); String sql; if (subQuery instanceof QueryBySQL) { sql = ((QueryBySQL) subQuery).getSql(); } else { sql = new DynamicSqlSelectStatement(this, getPlatform(), cld, subQuery, getLogger()).getStatement(); } return sql; } You have to build your own strategie. I will post our strategies soon. Greetings, CL -----Original Message----- From: Janssen, Roger [mailto:[EMAIL PROTECTED] Sent: Mittwoch, 05. März 2008 15:02 To: OJB Users List Subject: RE: Is it possible to force OJB not use execute a prepared statement? Hi Christian, The problem, I believe, is with the number of parameters (parameter markers) that crosses a certain boundary. We ran into an upper limit of 2000 (or something like that) on MSSQL server. That is a problem for us because we sometimes generate queries that have more parameters (yes... really), and then MSSQL server throws an exception. So, I am very interested in your solution. It could help solve our problem as well. Roger Janssen iBanx -----Original Message----- From: Christian Lipp [mailto:[EMAIL PROTECTED] Sent: Wednesday, March 05, 2008 2:27 PM To: 'OJB Users List' Subject: Potential SPAM:RE: Is it possible to force OJB not use execute a prepared statement? Hi Roger, OJB uses alsways prepared statements as armin said before, but do you have problems with the prepared statements or with the count of parameter markers (? in the where clause)? I am asking because we did a lot of experiments with different implementations (or specialisations) of SqlGeneratorDefaultImpl. The first implementation was not using parameter markers at all. So we used prepared statements without any parameter markers, which comes close to dynamic statements (at least in my understanding and I think this is what you need). I would like to post what we did to discuss it here on the mailing list (we are using db2 and could increase the performance 40% in online acces and 50% in batch access). 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