PersistenceManager Cache

Question

I just want to know how the persistence manager maintains cache.
1.When i get the instance of persistence manager,during that time itself,all
the JDO instances will be loaded in cache??
or lazy loading???Like only when a request to get an extent of a JDO
comes,then only the instances will be loaded in cache??
2.How about Query Results??All the results will be loaded and returned or
Lazy loading as you traverse thru the result list??
Srini

Answer 1

See inline:
Srini wrote:
I just want to know how the persistence manager maintains cache.
1.When i get the instance of persistence manager,during that time itself,all
the JDO instances will be loaded in cache??No. The PersistenceManager's cache is a lazy one. It maintains a
growing blob of data.
or lazy loading???Like only when a request to get an extent of a JDO
comes,then only the instances will be loaded in cache??Yes. However, extents can be lazily loaded depending on if your
database supports scrolling resultsets.
2.How about Query Results??All the results will be loaded and returned or
Lazy loading as you traverse thru the result list??Same as an extent.
>
SriniNow here are some things to note:
You can always boot an object from the PersistenceManager's cache...
for example:
     Extent e = pm.getExtent (Foo.class, true);
     for (Iterator i = e.iterator (); i.hasNext ();)
          pm.evict (i.next ());
     e.closeAll ();
Should have a small size cache (depending on state before this code block).
Also, we have PersistenceManagerFactory caching which is another layer
below, for those who have bought the feature (which is included in our
enterprise package) which stores objects in a more durable manner.
Stephen Kim
[email protected]
SolarMetric, Inc.
http://www.solarmetric.com