23. Statistics

Hibernate can gather all sorts of statistics which can help you get a better insight into what Hibernate does behind the scenes.

By default, the statistics are not collected because this incurs an additional processing and memory overhead. To instruct Hibernate to start collecting statistics, you need to set the hibernate.generate_statistics configuration property to true:

<property
    name="hibernate.generate_statistics"
    value="true"
/>

23.1. org.hibernate.stat.Statistics methods

The Hibernate statistics are made available via the Statistics interface which exposes the following methods:

23.1.1. General statistics methods

isStatisticsEnabled

Are statistics enabled?

setStatisticsEnabled(boolean b)

Enable statistics based on the provided parameter.

clear

Reset all statistics.

logSummary

Print a summary of the current statistics into the application log.

getStartTime

The milliseconds (JVM standard currentTimeMillis()) since the initial creation of this Statistics instance or the last time clear() was called.

23.1.2. Aggregated statistics methods

getQueries

Get executed query strings. The maximum number of queries tracked by the Hibernate statistics is given by the hibernate.statistics.query_max_size property.

getEntityStatistics(String entityName)

Find entity statistics for the given name.

getCollectionStatistics(String role)

Get collection statistics per role (collection name).

getNaturalIdStatistics(String entityName)

Get the Hibernate-specific natural id resolution statistics for the given entity.

getQueryStatistics(String queryString)

Get the statistics for the given query string (JPQL/HQL or native SQL).

getDomainDataRegionStatistics(String regionName)

Get the second-level cache statistics per domain data (entity, collection, natural-id) region.

getQueryRegionStatistics(String regionName)

Get the second-level cache statistics per query region.

getCacheRegionStatistics(String regionName)

Get statistics for either a domain-data or query-result region (this method checks both, preferring domain data region if one exists).

23.1.3. SessionFactory statistics methods

getEntityNames

Get the names of all entities configured with the current SessionFactory.

getCollectionRoleNames

Get the names of all collection roles configured with the current SessionFactory.

23.1.4. Session statistics methods

getSessionCloseCount

Global number of sessions that got closed.

getSessionOpenCount

Global number of sessions that got opened.

getFlushCount

Get the global number of flush operations executed (either manual or automatic).

23.1.5. JDBC statistics methods

getPrepareStatementCount

The number of JDBC prepared statements that were acquired by Hibernate.

getCloseStatementCount

The number of JDBC prepared statements that were released by Hibernate.

getConnectCount

Get the global number of connections acquired by the Hibernate sessions (the actual number of connections used may be much smaller depending whether you use a connection pool or not).

23.1.6. Transaction statistics methods

getSuccessfulTransactionCount

The number of transactions that completed successfully.

getTransactionCount

The number of transactions we know to have completed.

23.1.7. Concurrency Control statistics methods

getOptimisticFailureCount

The number of Hibernate StaleObjectStateExceptions or JPA OptimisticLockExceptions that occurred.

23.1.8. Entity statistics methods

getEntityDeleteCount

Get the global number of entity deletes.

getEntityInsertCount

Get the global number of entity inserts.

getEntityLoadCount

Get the global number of entity loads.

getEntityFetchCount

Get the global number of entity fetches.

getEntityUpdateCount

Get the global number of entity updates.

23.1.9. Collection statistics methods

getCollectionLoadCount

Global number of collections that were loaded.

getCollectionFetchCount

Global number of collections that were fetched.

getCollectionUpdateCount

Global number of collections that were updated.

getCollectionRemoveCount

Global number of collections that were removed.

getCollectionRecreateCount

Global number of collections that were recreated.

23.1.10. Query statistics methods

getQueryExecutionCount

Get the global number of executed queries.

getQueryExecutionMaxTime

Get the time in milliseconds of the slowest query.

getQueryExecutionMaxTimeQueryString

Get the query string for the slowest query.

getQueryPlanCacheHitCount

Get the global number of query plans successfully retrieved from cache.

getQueryPlanCacheMissCount

Get the global number of query plans lookups not found in cache.

23.1.11. Natural id statistics methods

getNaturalIdQueryExecutionCount

Get the global number of natural id queries executed against the database.

getNaturalIdQueryExecutionMaxTime

Get the global maximum query time for natural id queries executed against the database.

getNaturalIdQueryExecutionMaxTimeRegion

Get the region for the maximum natural id query time.

getNaturalIdQueryExecutionMaxTimeEntity

Get the entity for the maximum natural id query time.

23.1.12. Second-level cache statistics methods

getSecondLevelCacheRegionNames

Get all second-level domain data cache region names.

getSecondLevelCacheHitCount

Global number of cacheable entities/collections successfully retrieved from the cache.

getSecondLevelCacheMissCount

Global number of cacheable entities/collections not found in the cache and loaded from the database.

getSecondLevelCachePutCount

Global number of cacheable entities/collections put in the cache.

Second-level cache natural id statistics methods

getNaturalIdCacheHitCount

Get the global number of cached natural id lookups successfully retrieved from cache.

getNaturalIdCacheMissCount

Get the global number of cached natural id lookups not found in cache.

getNaturalIdCachePutCount

Get the global number of cacheable natural id lookups put in cache.

Second-level cache query statistics methods

getQueryCacheHitCount

Get the global number of cached queries successfully retrieved from cache.

getQueryCacheMissCount

Get the global number of cached queries not found in cache.

getQueryCachePutCount

Get the global number of cacheable queries put in cache.

Second-level cache timestamp statistics methods

getUpdateTimestampsCacheHitCount

Get the global number of timestamps successfully retrieved from cache.

getUpdateTimestampsCacheMissCount

Get the global number of timestamp requests that were not found in the cache.

getUpdateTimestampsCachePutCount

Get the global number of timestamps put in cache.

23.2. Query statistics max size

Traditionally, Hibernate stored all executed queries when statistics were enabled. However, this was a very bad default since, if your application runs millions of different queries, you’d risk running out of memory.

Therefore, to restrict the number of queries the Hibernate statistics can hold, the hibernate.statistics.query_max_size property was added. By default, the maximum number of queries retained is 5000, but you can increase this value via the hibernate.statistics.query_max_size property.

So, if your application makes heavy use of the JPA Criteria API or if you simply have a very large number of queries, you might want to raise the maximum number of queries that are being stored by the Statistics instance.

If the maximum number of queries has been reached, Hibernate uses a Least recently used (LRU)) policy to make room for new query entries.

23.3. Query plan cache statistics

Every entity query, be it JPQL/HQL or Criteria API, is compiled to an AST (Abstract Syntax Tree), and this process is resource-intensive. To speed up the entity query executions, Hibernate offers a query plan cache so that compiled plans can be reused.

To monitor the query plan cache you have the following statistics.

23.3.1. Query plan cache global statistics

The Statistics instance provides two global counters which can give you an overall picture of the query plan cache effectiveness.

• getQueryPlanCacheHitCount

• getQueryPlanCacheMissCount

If the hit count is high and the miss count is low, then the query plan cache is effective, and the vast majority of entity queries are served from the query plan cache, rather than being compiled over and over again.

23.3.2. Query plan cache query-level statistics

The QueryStatistics instance, which you can get via the getQueryStatistics(String queryString) method of the Statistics object, stores the following query plan cache metrics:

getPlanCacheHitCount

The number of query plans successfully fetched from the cache.

getQueryPlanCacheMissCount

The number of query plans not fetched from the cache.

getPlanCompilationTotalMicroseconds

The overall time spent to compile the plan for this particular query.