Update migration-guide.adoc
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@ -300,7 +300,45 @@ Storing just the identifiers in the query-cache has a major drawback when fetchi
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Starting in 6.0, we now store the complete set of data for the entity into the query-cache. This also can have a drawback related to the size of caches. We plan to address this further in later 6.x releases to allow storing just the identifiers along the lines of the previous behavior.
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A related change in 6.0 is the fact that queries no longer populate the second-level cache region for any returned entities or collections. This is again something we plan to address in later 6.x releases.
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E.g.
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```
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Statistics stats = sessionFacroty.getStatistics();
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// First time the query is executed, query and results are cached and both the query and entity chache will be populated.
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TypedQuery<Employee> query = session.createQuery( "select e from Employee e", Employee.class )
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.setHint( HINT_CACHEABLE, true );
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List<Employee> employees = query.getResultList();
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assertEquals( 1, employees.size() );
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assertEquals( 0, stats.getQueryCacheHitCount() );
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assertEquals( 1, stats.getQueryCacheMissCount() );
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assertEquals( 1, stats.getQueryCachePutCount() ); // query cache is populated.
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assertEquals( 0, stats.getSecondLevelCacheHitCount() );
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assertEquals( 0, stats.getSecondLevelCacheMissCount() );
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assertEquals( 1, stats.getSecondLevelCachePutCount() ); // entity cache is populated as well.
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stats.clear();
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// Second time the same query is executed only the query cache will be hit.
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TypedQuery<Employee> query = session.createQuery( "select e from Employee e", Employee.class )
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.setHint( HINT_CACHEABLE, true );
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List<Employee> employees = query.getResultList();
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assertEquals( 1, employees.size() );
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assertEquals( 1, stats.getQueryCacheHitCount() ); // the query cache is hit.
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assertEquals( 0, stats.getQueryCacheMissCount() );
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assertEquals( 0, stats.getQueryCachePutCount() );
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assertEquals( 0, stats.getSecondLevelCacheHitCount() );
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assertEquals( 0, stats.getSecondLevelCacheMissCount() );
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assertEquals( 0, stats.getSecondLevelCachePutCount() ); // No need to hit the entity cache because the query cache contains all the entity data.
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```
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[[query-sqm]]
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== SQM (HQL/Criteria)
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