Retrieve a set of specific objects

Question

I am looking for a way in JDO to retrieve and update sets of specific
objects using a single SQL statement of the form:
SELECT * FROM <ManagedEntity> WHERE <pk> IN (<pk1,pk2,...>)
This is a relatively frequent and important use case for the types of
applications that deal with graphs, such as for modeling telecommunications
networks. I will describe below the specific behavior as taken from JSR 142:
OSS Inventory API, specifically the Resource Inventory EJB Session Facade.
(See http://jcp.org/jsr/detail/142.jsp and
http://jcp.org/jsr/detail/144.jsp, which defines the API design patterns
followed by http://java.sun.com/products/oss/ .)
(1) ResourceInventoryEntityValue[]
getResourceInventoryEntitiesByKeys(ResourceInventoryEntityKey[] keys,
String[] attrNames)
This is one occurrence of the operation pattern get<ManagedEntities>ByKeys.
When the ResourceInventoryEntityValue implementation is a JDO
PersistenceCapable class, and the ResourceInventoryEntityKey holds the
primary key of each object of interest, the result set should be selected
with a single SQL statement.
(2) void removeResourceInventoryEntitiesByKeys (ResourceInventoryEntityKey[]
keys)
This is one occurrence of the operation pattern
remove<ManagedEntities>ByKeys. The identified instances should be deleted
with a single SQL statement.
The problem is I do not see any obvious JDOQL syntax or operations on the
JDO interfaces that would allow me to accomplish the above. On the positive
side, Kodo is handling the other patterns extremely elegantly (pretty Java
in WebLogic Server) and efficiently (pretty SQL). It is only this one ByKeys
pattern that I can't see a way of doing nicely in JDO.
Any help would be appreciated.
Ben

Answer 1

Thanks Abe. Your response was most helpful.
Ben
"Abe White" <[email protected]> wrote in message
news:[email protected]...
Actually, JDOQL does offer a way of doing what you want assuming you'reusing
application identity and you use only a single primary key field:
q.declareParameters ("Collection pks");
q.setFilter ("pks.contains (myPKField)");
Collection results = (Collection) filter.execute (pkCollection);
Now the bad news: Collection parameters were added to the spec between the
proposed final draft and the 1.0 release, and the were not noted in the
spec ChangeLog. Unfortunately, that means that we here at Solarmetricdidn't
notice the addition until someone pointed it out to us recently, and we
haven't implemented it yet. Or actually, we've implemented it internally
as part of a major query rework, but it won't be available publicly for
awhile. You do, however, have other options:
You could do it with "||" clauses:
StringBuffer filter = new StringBuffer ();
for (Iterator itr = pks.iterator (); itr.hasNext ();)
filter.append (pkFieldName).append (" == ").append (itr.next ());
if (itr.hasNext ())
filter.append (" || ");
q.setFilter (filter.toString ());
Collection results = (Collection) q.execute ();
You can also use our filter extensions (assuming you have the enterprise
edition or have purchased the filter extensions module). You could usethe
lit:sqlEmbed extension to embed whatever custom SQL you wanted:
q.setFilter ("lit:sqlEmbed (\"IDX IN (...)\")");
Collection results = (Collection) q.execute ();
Good luck.
I am looking for a way in JDO to retrieve and update sets of specific
objects using a single SQL statement of the form:
SELECT * FROM <ManagedEntity> WHERE <pk> IN (<pk1,pk2,...>)
This is a relatively frequent and important use case for the types of
applications that deal with graphs, such as for modeling
telecommunications
networks. I will describe below the specific behavior as taken from JSR142:
OSS Inventory API, specifically the Resource Inventory EJB SessionFacade.
(See http://jcp.org/jsr/detail/142.jsp and
http://jcp.org/jsr/detail/144.jsp, which defines the API design patterns
followed by http://java.sun.com/products/oss/ .)
(1) ResourceInventoryEntityValue[]
getResourceInventoryEntitiesByKeys(ResourceInventoryEntityKey[] keys,
String[] attrNames)
This is one occurrence of the operation patternget<ManagedEntities>ByKeys.
When the ResourceInventoryEntityValue implementation is a JDO
PersistenceCapable class, and the ResourceInventoryEntityKey holds the
primary key of each object of interest, the result set should beselected
with a single SQL statement.
(2) void removeResourceInventoryEntitiesByKeys(ResourceInventoryEntityKey[]
keys)
This is one occurrence of the operation pattern
remove<ManagedEntities>ByKeys. The identified instances should bedeleted
with a single SQL statement.
The problem is I do not see any obvious JDOQL syntax or operations onthe
JDO interfaces that would allow me to accomplish the above. On thepositive
side, Kodo is handling the other patterns extremely elegantly (prettyJava
in WebLogic Server) and efficiently (pretty SQL). It is only this oneByKeys
pattern that I can't see a way of doing nicely in JDO.
Any help would be appreciated.
Ben