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https://issues.apache.org/jira/browse/OPENJPA-738?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael Dick resolved OPENJPA-738.
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Resolution: Fixed
> QueryCache Improvement
> ----------------------
>
> Key: OPENJPA-738
> URL: https://issues.apache.org/jira/browse/OPENJPA-738
> Project: OpenJPA
> Issue Type: Improvement
> Components: datacache
> Affects Versions: 1.2.0, 1.2.1, 1.3.0
> Reporter: Sandhya
> Assignee: Michael Dick
> Fix For: 1.3.0
>
> Attachments: OPENJPA-738.10.patch, OPENJPA-738.11.patch,
> OPENJPA-738.2.patch, OPENJPA-738.3.patch, OPENJPA-738.6.patch,
> OPENJPA-738.7.patch, OPENJPA-738.8.patch, OPENJPA-738.patch
>
>
> Hi All,
>
> I have changed the jpa code to eliminate the scan of the jpa query
> cache to invalidate cached queries that is triggered by entity bean values
> changes. The problem with the current code is that whenever an entity bean
> value changes, the query cache needs to be scanned and all the queries that
> are related to the changed entity bean should be invalidated. This is
> resulting in poor performance when the querycache has too many queries in it.
>
> The new approach is to track the timestamp of the query and the
> timestamp of last update for each entity class and compare the timestamps
> when retrieving the query for reuse. If the timestamp of the query result is
> older than the last update time of any entity in the access path of the
> query, the query result would not be reused and the query result would be
> evicted from the query cache.
>
> I introduced a configurable attribute in the persistence.xml in
> QueryCache property "evictOnTimestamp=true". Therefore the QueryCache
> property in persistence.xml file looks as follows:
>
> <property name="openjpa.QueryCache" value = "CacheSize=1000,
> evictOnTimestamp=true" />
>
> If the "evictOnTimestamp" value is set to true in the xml file the new
> code is invoked otherwise the old code. The default behaviour would be the
> old code. That is the value for "evictOnTimestamp" is false by default so
> that if this property is not set persistence.xml, old code gets invoked.
>
> In the process of changing the code to evict the queries using the
> timestamp, I had to introduce 4 methods in QueryCache interface. We want this
> change to be applied to JPA trunk and 1.2.x branch. Anyone who is extending
> the QueryCache that implements this interface would have to implement these 4
> methods. Please respond as soon as possible if this interface change is an
> issue.
>
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