This is minor bug fixes and feature enhancements release. The main change is the ability to place Message elements in the Data Dictionaries where they can be referenced by many Operations from unrelated Services.
This is the major feature enhancement release. The main new feature is the ability to model and generate support for events - the unsolicited asyncroneous messages produced by servers and consumed by clients.
Subqueries are not fully implemented in MySQL 4.1.3-beta or earleir
Author
Message
Adjutant
Date:
Wed Aug 11, 2004 06:26 AM
Subject:
Subqueries are not fully implemented in MySQL 4.1.3-beta or earleir
In order to take full advantage of the Domain Object layer library genertaed by MetaBoss, one has to use
the database which fully supports subqueries. Unfortunately MySQL 4.1.3-beta and earlier does not support IN and LIMIT clauses in subqueries. This means that some complex queries will fail on MySQL and the queries will have to be broken into a number of smaller and simpler queries (or alternatively another brand of database will have to be used).
For example. Suppose that we have a simple "Client" and "Order" entities with "Client Places Orders" association between them. The query "Select all Clients who has placed last ten Orders" will fail on MySQL because it will need to use LIMIT clause in the subquery. The fix (quite inefficient) is to run simple "Select last ten Orders" query and then get placing Client for each Order.
Please note that this is a run-time error (MetaBoss queries are built dynamically and therefore generator and compiler are unable to catch this situation). When MySQL is unable to process the query issued by middleware it throws back the SQLException with the text " Syntax error or access violation, message from server: This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery'"
Please also note that MySQL online manual at http://dev.mysql.com/doc/mysql/en/Subquery_errors.html claims that this exception only occurs in "some early versions, such as MySQL 4.1.1". We ,however, have found that it still occurs in 4.1.3-beta. Moreover, our study of the MySQL release notes history has not revealed any mention that this limitation has been removed.
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