oracle.toplink.essentials.config.FlushClearCache Maven / Gradle / Ivy

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package oracle.toplink.essentials.config;

/**
 * FlushClearCache persistence property
 * defines modes of cache handling after em.flush call followed by em.clear call.
 * This property could be specified while creating either EntityManagerFactory 
 * (createEntityManagerFactory or persistence.xml)
 * or EntityManager (createEntityManager); the latter overrides the former.
 * 
 * JPA persistence property Usage:
 * 
 * 
properties.add(TopLinkProperties.FLUSH_CLEAR_CACHE, FlushClearCache.Drop);
 * 
 * Values are case-insensitive.
 * "" could be used instead of default value FlushClearCache.DEFAULT.
 */
public class FlushClearCache {
    /** Call to clear method causes to drop from EntityManager cache only the objects that haven't been flushed.
     * This is the most accurate mode: shared cache is perfect after commit; 
     * but the least memory effective: smbd repeatedly using flush followed by clear
     * may eventually run out of memory in a huge transaction.
     */
    public static final String  Merge = "Merge";
    
    /** Call to clear method causes to drop the whole EntityManager cache.
     * This is the fasteset and using the least memory mode - 
     * but after commit the shared cache potentially contains stale data.
     */
    public static final String  Drop = "Drop";

    /** Call to clear method causes to drops the whole EntityManager cache, 
     * on commit the classes that have at least one object updated or deleted 
     * are invalidated in the shared cache.
     * This is a compromise mode: potentially a bit slower than drop,
     * but has virtually the same memory efficiency.
     * After commit all potentially stale data is invalidated in the shared cache.
     */
    public static final String  DropInvalidate = "DropInvalidate";
 
    public static final String DEFAULT = DropInvalidate;
}