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Query Hints not working in Eclipse Link 2.3.2/2.6.1 when used to fetch data from second level Cache Used Hints,

@QueryHint(name = "javax.persistence.cache.retrieveMode", value = "USE"),
@QueryHint(name = "javax.persistence.cache.storeMode ", value = "USE")

Tried with below options.

1. Added JPA Hints to Named query itself
@NamedQuery(
name = TestEntity.FIND_BY_CODE,
query = "select t from Test t where t.code = :code",
hints = {
@QueryHint(name = "javax.persistence.cache.retrieveMode", value = "USE"),
@QueryHint(name = "javax.persistence.cache.storeMode ", value = "USE") })

2. Adding hints to the Entity Manager Itself after injecting it
em.setProperty("javax.persistence.cache.retrieveMode", CacheRetrieveMode.USE);
em.setProperty("javax.persistence.cache.storeMode", CacheRetrieveMode.USE);

3. Added JPA hints at the time of Query execution
em.createNamedQuery(TestEntity.FIND_BY_CODE,
AlertCategoryType.class).setHint("javax.persistence.cache.retrieveMode", CacheRetrieveMode.USE)
.setHint("javax.persistence.cache.storeMode", CacheStoreMode.USE)
.setParameter("code", code).getSingleResult();

None of the above usage of hints worked. Then i tried debugging on three different options what i found is, the Data Base Query which formed after setting these hints is passing hints as key/value pair below. 

eclipselink.query.hints => {javax.persistence.cache.retrieveMode=USE,                                                                                                                      javax.persistence.cache.storeMode=USE}

Where eclipselink.query.hints is the key even when we have set the JPA hints. This is something we don't have control over to change this.
But when i pass Eclipse Link provided hints as below , It started working as expected and the Results are fetched from Cache and not from the DB. 

eclipselink.query.hints => {eclipselink.query-results-cache.size=500, eclipselink.query-results-cache=true}

It means That When we use Eclipse Link it only recognizes Eclipse Link provided hints according to the key[ above shown] we see in Query.

Please suggest any work around to get the JPA Hints working

Environment I'm using is

  • Eclispe Link 2.3.2/2.6.1
  • Runnin fin serve Glassfish 4.1[payara]
  • Java8/JEE7
Vittal B
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1 Answers1

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The query hint you state is working (eclipselink.query-results-cache) is completely unrelated - it creates a new cache for the query results so that next time you execute that same query, the results are already there, so it does not need to execute the query again. This is outside (above an beyond) the second level cache.

The settings you refer to as not working affect the second level cache. Without more information, I'm going to state they are likely working as expected. Just because your query goes to the database does not mean the cache isn't being used. Caching entities is very different than caching the results to a query. If the query results are not cached, unless you have in-memory querying enabled, most read-all type queries must go to the database to determine what entities need to be built and returned. EclipseLink will then use those results to check the cache- if the entities already exist, they are returned as is - this avoids the overhead of rebuilding entities from the data.

You can check if your entity has been cached by using a em.find() or read query that uses the ID value. The cache is indexed by ID, so it will not need to go to the database to figure out which entities you want.

Chris
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