Package org.hibernate.stat.internal

Class StatsNamedContainer<V>

java.lang.Object

org.hibernate.stat.internal.StatsNamedContainer<V>

public final class StatsNamedContainer<V>
extends Object

Decorates a ConcurrentHashMap implementation to make sure the methods are being used correctly for the purpose of Hibernate's statistics. In particular, we do like the semantics of ConcurrentHashMap.computeIfAbsent(K, java.util.function.Function<? super K, ? extends V>) but not its performance.

See HHH-13527.

Constructor Summary

Constructors

Constructor	Description
StatsNamedContainer()	Creates an unbounded container - based on ConcurrentHashMap
StatsNamedContainer(int capacity, int concurrencyLevel)	Creates a bounded container - based on BoundedConcurrentHashMap

Method Summary

Modifier and Type	Method	Description
void	clear()
@Nullable V	get(String key)
@Nullable V	getOrCompute(String key, Function<String,V> function)	Similar semantics as you'd get by invoking ConcurrentMap.computeIfAbsent(Object, Function), but we check for the key existence first.
String[]	keysAsArray()	This method is inherently racy and expensive.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

StatsNamedContainer

public StatsNamedContainer(int capacity,
 int concurrencyLevel)

Creates a bounded container - based on BoundedConcurrentHashMap

StatsNamedContainer

public StatsNamedContainer()

Creates an unbounded container - based on ConcurrentHashMap

Method Details

clear

public void clear()

keysAsArray

public String[] keysAsArray()

This method is inherently racy and expensive. Only use on non-hot paths, and only to get a recent snapshot.

Returns:

all keys in string form.

getOrCompute

public @Nullable V getOrCompute(String key,
 Function<String,V> function)

Similar semantics as you'd get by invoking ConcurrentMap.computeIfAbsent(Object, Function), but we check for the key existence first. This is technically a redundant check, but it has been shown to perform better when the key existing is very likely, as in our case. Most notably, the ConcurrentHashMap implementation might block other accesses for the sake of making sure the function is invoked at most once: we don't need this guarantee, and prefer to reduce risk of blocking.

get

public @Nullable V get(String key)