Task overview: Data Studio pureQuery

Data Studio pureQuery provides Java™ Persistence API (JPA) with an alternative way to access a database. PureQuery supports static Structured Query Language (SQL).

About this task

JPA in the Java EE and Java SE environments provides optional support for the DB2® pureQuery runtime environment. PureQuery is a high performance Java data access platform that helps manage applications that access data. PureQuery provides an alternate set of APIs that can be used instead of Java Database Connectivity (JDBC) to access the DB2 database.

To use this feature on the application server, Data Studio pureQuery runtime version 1.2 must be installed. If you plan to perform the DB2 bind command from the administrative console, or with the wsadmin tool, you must have pureQuery v1.2 or later. Refer to the Data Studio information center topic on installing pureQuery Runtime for more information.

The application server offers support for static SQL for Enterprise JavaBeans™ (EJB) 2.x entity beans with the ejbdeploy SQLj option. With JPA, this feature is offered through pureQuery.

There are several benefits to using pureQuery instead of JDBC and SQLJ. Static SQL offers greater security and control over access to data because applications are only granted authority to execute known SQL. Static SQL offers better resource utilization on the DB2 server because it avoids runtime parsing and optimizing of the SQL statements.

PureQuery makes use of DB2 packages. These packages consist of information for one or more SQL statements and are stored in the DB2 catalog. To create the packages, the user must first run the wsdb2gen command on a JPA application. The wsdb2gen command creates a persistence_unit_name.pdqxml file. This file contains pre-generated SQL statements for Create, Update, Delete, and Retrieve, NamedQueries and NamedNativeQueries of JPA entities. The persistence_unit_name.pdqxml file must be bound against database. Associated DB2 packages are generated and the SQL statement is executed statically at runtime. This persistence_unit_name.pdqxml file can be included into the application Java archive (JAR) file.

When doing the bind process and when you define your JDBC provider, the following four Java archive (JAR) files must be in the class path:
  • db2jcc_license_cisuz.jar
  • db2jcc_license_cu.jar
  • pdq.jar
  • pdqmgmt.jar
Attention: Read more about the DB2 JAR level compliance for pureQuery at the IBM® Support Web site: System requirements for IBM Optim™ pureQuery Runtime for Linux®, UNIX®, and Windows®.

WebSphere® Application Server support for pureQuery

Restriction:
  • There is no support for the QueryTimeout property specified either through the FetchPlan API or through the property plug-in string for wsjpa.ConnectionFactoryProperties. The QueryTimeout value is ignored if specified.
  • OpenJPA large result processing uses JDBC APIs for scrollable cursors.
Important:
  • JPA sets the pureQuery property, pdq.executionMode, to the value STATIC.
  • In addition to the JDBC driver JAR file, the JDBC provider configuration must include the JAR file for the pureQuery runtime environment.
  • OpenJPA provides support to allow application programs to programmatically access and alter the FetchPlan at run time. Altering the fetch plan might result in an SQL that has not been generated by the wsdb2gen command at application build time. If this occurs, the SQL is executed dynamically rather than using static SQL from the DB2 package.
  • If the user makes changes to the application queries, entity mapping or persistence properties, run the wsdb2gen command and bind again. This process generates and binds the updated DB2 packages.
  • Input parameter values in JPA queries (with both EJB SQL queries and native SQL queries) cannot be NULL values except in the case of update statements SET expression values. To search for NULL values in a WHERE clause of SELECT, UPDATE or DELETE, then enter the is null predicate instead.

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Last updated: Oct 21, 2010 5:30:17 AM CDT
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