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From Brian McCallister <mccallis...@forthillcompany.com>
Subject Ignore Cache option on Query
Date Thu, 08 Jul 2004 03:51:45 GMT
Thinking about the fieldwise cache, and JDO2, and some other thoughts, 
I think we need to have a flag on queries that specifies that the query 
is to ignore the *second level* cache.

One optimization I would really like to make on a really aggressive 
cache (say an aggressive version of the FieldCache mentioned in earlier 
email) is to allow the cache to issue queries if it knows it needs 
specific instances.

For example, the cache is queried for an instance of Foo which it 
contains. The cache instantiates foo, sets the correct values, and sees 
it needs a collection. It has the collection in it as a set of identity 
instances. The collection may contain 15 items, 10 of which it knows it 
has in the cache. It would be nice for the cache to be able to go grab 
the remaining 5 items by a specific query rather than issue the more 
general criteria based query for the whole collection.

This requires being able to ignore the cache though as it would need to 
issue query on same broker to maintain the transaction, but then it 
would cycle back into itself. This may actually be okay -- as it 
specifically formed the query to ask for things it doesn't have.

Anyway, aside from that, JDO2 requires the ability to ignore second 
level cache in a query =)


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