Using cache just for some classes

Question

Hi,
I'd like to use datastore cache just for some persistent objects. The
cache should be active just for some objects and disabled for some other
objects.
The only one way I found is the following: I defined the default cache
time-out to 0 millisecs and this value is overridden for a particular
class in the jdo metadata.
For example, these are the global properties:
     <config-property name="dataCache" value="true"/>
     <config-property name="dataCacheTimeout" value="0"/>
and this is the jdo metadata:
<extension vendor-name="kodo" key="data-cache-timeout" value="10000"/>
It works, but I don't like it. I'd like to turn off the cache in some way
for classes that doesn't need it. I tryed to create a custom cache in this
way:
<config-property name="dataCache" value="false, true(Name=myCache)"/>
or
<config-property name="dataCache" value="false(Name=default),
true(Name=myCache)"/>
but Kodo says that a cache named "default" must be configured and error is
raised.
What happens when the cache timeout is 0? If the cache is read every time
with 0 hits, I think that this is no good for performances, it would be
better not reading the cache at all...

Answer 1

Your best bet is to use the data-cache metadata extension in those
classes that you don't want cached:
<class name="MyVolatileClass">
<extension vendor-name="kodo" key="data-cache" value="false"/>
</class>
If most of your classes should not be cached, you could also set the
default cache's size (and soft reference size) to zero. This will,
however, incur a small performance overhead.
-Patrick
Claudio Tasso wrote:
Hi,
I'd like to use datastore cache just for some persistent objects. The
cache should be active just for some objects and disabled for some other
objects.
The only one way I found is the following: I defined the default cache
time-out to 0 millisecs and this value is overridden for a particular
class in the jdo metadata.
For example, these are the global properties:
     <config-property name="dataCache" value="true"/>
     <config-property name="dataCacheTimeout" value="0"/>
and this is the jdo metadata:
<extension vendor-name="kodo" key="data-cache-timeout" value="10000"/>
It works, but I don't like it. I'd like to turn off the cache in some way
for classes that doesn't need it. I tryed to create a custom cache in this
way:
<config-property name="dataCache" value="false, true(Name=myCache)"/>
or
<config-property name="dataCache" value="false(Name=default),
true(Name=myCache)"/>
but Kodo says that a cache named "default" must be configured and error is
raised.
What happens when the cache timeout is 0? If the cache is read every time
with 0 hits, I think that this is no good for performances, it would be
better not reading the cache at all...