High-Performance Hibernate - JDK.io 2018

@vlad_mihalcea vladmihalcea.com
High-Performance
Hibernate
VLAD MIHALCEA

About me
vladmihalcea.com

Performance Facts
“More than half of application performance
bottlenecks originate in the database”
AppDynamics - http://www.appdynamics.com/database/

Google Ranking
“Like us, our users place a lot of value in speed –
that's why we've decided to take site speed
into account in our search rankings”
https://webmasters.googleblog.com/2010/04/using-site-speed-in-web-search-ranking.html

Performance and Revenue
“It has been reported that every 100ms of latency
costs Amazon 1% of profit”
http://radar.oreilly.com/2008/08/radar-theme-web-ops.html

Agenda
• Performance and Response Time
• Connection providers
• Identifier generators
• Relationships
• Batching
• Fetching
• Caching

The anatomy of a database transaction

Response Time
• connection acquisition time
• statement submit time
• statement execution time
• result set fetching time
• idle time prior to releasing database connection
𝑇 = 𝑡 𝑎𝑐𝑞 + 𝑡 𝑟𝑒𝑞 + 𝑡 𝑒𝑥𝑒𝑐 + 𝑡 𝑟𝑒𝑠 + 𝑡𝑖𝑑𝑙𝑒

Connection Management
Metric DB_A (ms) DB_B (ms) DB_C (ms) DB_D (ms) HikariCP (ms)
min 11.174 5.441 24.468 0.860 0.001230
max 129.400 26.110 74.634 74.313 1.014051
mean 13.829 6.477 28.910 1.590 0.003458
p99 20.432 9.944 54.952 3.022 0.010263

Connection Providers

DataSourceConnectionProvider

Connection Provisioning

FlexyPool
• concurrent connections
• concurrent connection requests
• connection acquisition time
• connection lease time histogram
• maximum pool size
• overflow pool size
• retries attempts
• total connection acquisition time
• Java EE
• Bitronix / Atomikos
• Apache DBCP / DBCP2
• C3P0
• BoneCP
• HikariCP
• Tomcat CP
• Vibur DBCP
https://github.com/vladmihalcea/flexy-pool

FlexyPool – Concurrent connection requests
1
28
55
82
109
136
163
190
217
244
271
298
325
352
379
406
433
460
487
514
541
568
595
622
649
676
703
730
757
784
811
838
865
892
919
946
973
1000
1027
0
2
4
6
8
10
12
Sample time (Index × 15s)
Connectionrequests
max mean p50 p95 p99

FlexyPool – Pool size growth
1
28
55
82
109
136
163
190
217
244
271
298
325
352
379
406
433
460
487
514
541
568
595
622
649
676
703
730
757
784
811
838
865
892
919
946
973
1000
1027
0
1
2
3
4
5
6
Maxpoolsize

FlexyPool – Connection acquisition time
1
28
55
82
109
136
163
190
217
244
271
298
325
352
379
406
433
460
487
514
541
568
595
622
649
676
703
730
757
784
811
838
865
892
919
946
973
1000
1027
0
500
1000
1500
2000
2500
3000
3500
Connectionacquisitiontime(ms)

FlexyPool – Connection lease time
1
29
57
85
113
141
169
197
225
253
281
309
337
365
393
421
449
477
505
533
561
589
617
645
673
701
729
757
785
813
841
869
897
925
953
981
1009
1037
0
5000
10000
15000
20000
25000
30000
35000
40000
Connectionleasetime(ms)

Connection acquisition

Resource-local connection acquisition

Immediate connection acquisition issue
@PersistenceContext
private EntityManager entityManager;
@Transactional
public void importForecasts(String dataFilePath) {
Document forecastXmlDocument = readXmlDocument( dataFilePath );
List<Forecast> forecasts = parseForecasts(forecastXmlDocument);
for(Forecast forecast : forecasts) {
entityManager.persist( forecast );
}
}

Resource-local delay connection acquisition
<property
name="hibernate.connection.provider_disables_autocommit"
value="true"
/>
• Hibernate 5.2.10 introduced resource-local delay connection
acquisition
• Requires the DataSource to disable auto-commit

JPA Identifier Generators
• IDENTITY
• SEQUENCE
• TABLE
• AUTO

IDENTITY
• In Hibernate, IDENTITY generator disables JDBC batch inserts
• MySQL 8.0 does not offer support for database SEQUENCE
• MariaDB 10.3 adds support for SEQUENCE objects

SEQUENCE
• Oracle, PostgreSQL, and even SQL Server 2012
• May use roundtrip optimizers: hi/lo, pooled, pooled-lo
• By default, Hibernate 5 uses the enhanced sequence generators
<property
name="hibernate.id.new_generator_mappings"
value="true"/>

The pooled optimizer
@Id
@GeneratedValue(
strategy = GenerationType.SEQUENCE,
generator = "pooled"
)
@SequenceGenerator(
name = "pooled",
allocationSize = 3
)
private Long id;

The pooled optimizer

SEQUENCE - Pooled optimizer (50 rows)
1 5 10 50
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Sequence increment size
Time(ms)

TABLE
• Uses row-level locks and a separate transaction/connection
• May use roundtrip optimizers: hi/lo, pooled, pooled-lo
• By default, Hibernate 5 uses the enhanced sequence generators
<property
name="hibernate.id.new_generator_mappings"
value="true"/>

TABLE - Pooled optimizer (50 rows)
1 5 10 50
0
0.5
1
1.5
2
2.5
3
Table increment size
Time(ms)

IDENTITY vs TABLE (100 rows)
• IDENTITY makes no use of batch inserts
• TABLE generator using a pooled optimizer with an increment size of
100

IDENTITY vs TABLE (100 rows)
1 2 4 8 16
0
500
1000
1500
2000
2500
Thread count
Time(ms)
Identity Table

AUTO: IDENTITY vs TABLE?
• Prior to Hibernate 5, AUTO would resolve to IDENTITY if the
database supports this feature
• Hibernate 5 uses TABLE generator if the database does not support
sequences
• So, pay attention when using MySQL or MariaDB (prior to 10.3)

SEQUENCE vs TABLE (100 rows)
• Both benefiting from JDBC batch inserts
• Both using a pooled optimizer with an increment size of 100

SEQUENCE vs TABLE (100 rows)
1 2 4 8 16
0
200
400
600
800
1000
1200
Thread count
Time(ms)
Sequence Table

Relationships

Batching
• SessionFactory setting
• Session-level configuration since Hibernate 5.2

Batching - SessionFactory
<property
name="hibernate.jdbc.batch_size"
value="5"/>
• Switching from non-batching to batching

Batching - Session
doInJPA( this::entityManagerFactory, entityManager -> {
entityManager.unwrap( Session.class )
.setJdbcBatchSize( 10 );
for ( long i = 0; i < entityCount; ++i ) {
Person = new Person( i, String.format( "Person %d", i ) );
entityManager.persist( person );
if ( i % batchSize == 0 ) {
entityManager.flush();
entityManager.clear();
}
}
} );

Batching
DEBUG [main]: n.t.d.l.SLF4JQueryLoggingListener –
Name:DATA_SOURCE_PROXY,
Time:1,
Success:True,
Type:Prepared,
Batch:True,
QuerySize:1,
BatchSize:10,
Query: ["insert into Person (name, id) values (?, ?)"],
Params:[
(Person 1, 1), (Person 2, 2), (Person 3, 3), (Person 4, 4), (Person 5, 5),
(Person 6, 6), (Person 7, 7), (Person 8, 8), (Person 9, 9), (Person 10, 10)
]

Insert PreparedStatement batching (5k rows)
1 10 20 30 40 50 60 70 80 90 100 1000
0
200
400
600
800
1000
1200
1400
1600
Batch size
Time(ms)
DB_A DB_B DB_C DB_D

Update PreparedStatement batching (5k rows)
1 10 20 30 40 50 60 70 80 90 100 1000
0
100
200
300
400
500
600
700
Batch size
Time(ms)
DB_A DB_B DB_C DB_D

Delete PreparedStatement batching (5k rows)
1 10 20 30 40 50 60 70 80 90 100 1000
0
200
400
600
800
1000
1200
Batch size
Time(ms)
DB_A DB_B DB_C DB_D

Batching - Cascading
<property
name="hibernate.order_inserts"
value="true"/>
<property
name="hibernate.order_updates"
value="true"/>

Batching – @Version
<property
name="hibernate.jdbc.batch_versioned_data"
value="true"/>
• Enabled by default in Hibernate 5
• Disabled in Hibernate 3.x, 4.x, and for Oracle 8i, 9i, and 10g
dialects

Fetching
• JDBC fetch size
• JDBC ResultSet size
• DTO vs Entity queries
• Fetching relationships

Fetching – JDBC Fetch Size
• Oracle – Default fetch size is 10
• SQL Server – Adaptive buffering
• PostgreSQL, MySQL – Fetch the whole ResultSet at once
• SessionFactory setting:
<property
name="hibernate.jdbc.fetch_size"
value="100"/>

Fetching - JDBC fetch size
• Query-level hint:
List<PostCommentSummary> summaries =
entityManager.createQuery(
"select new PostCommentSummary( " +
" p.id, p.title, c.review ) " +
"from PostComment c " +
"join c.post p")
.setHint(QueryHints.HINT_FETCH_SIZE, fetchSize)
.getResultList();

Fetching – JDBC Fetch Size (10k rows)
1 10 100 1000 10000
0
100
200
300
400
500
600
Fetch size
Time(ms)
DB_A DB_B DB_C DB_D

Fetching – Pagination
• JPA / Hibernate API works for both entity and native queries
List<PostCommentSummary> summaries =
entityManager.createQuery(
"select new PostCommentSummary( " +
" p.id, p.title, c.review ) " +
"from PostComment c " +
"join c.post p")
.setFirstResult(pageStart)
.setMaxResults(pageSize)
.getResultList();

Fetching – 100k vs 100 rows
Fetch all Fetch limit
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Time(ms)
DB_A DB_B DB_C DB_D

Fetching – Pagination
• Hibernate uses OFFSET pagination
• Keyset pagination scales better when navigating large result sets
• http://use-the-index-luke.com/no-offset

Fetching – Entity vs Projection
• Selecting all columns vs a custom projection
SELECT *
FROM post_comment pc
INNER JOIN post p ON p.id = pc.post_id
INNER JOIN post_details pd ON p.id = pd.id
SELECT pc.version
FROM post_comment pc
INNER JOIN post p ON p.id = pc.post_id
INNER JOIN post_details pd ON p.id = pd.id

Fetching – Entity vs Projection
All columns Custom projection
0
5
10
15
20
25
30
Time(ms)
DB_A DB_B DB_C DB_D

Fetching – DTO Projections
• Read-only views
• Tree structures (Recursive CTE)
• Paginated Tables
• Analytics (Window functions)

Fetching – Entity Queries
• Writing data
• Web flows / Multi-request logical transactions
• Application-level repeatable reads
• Detached entities / PersistenceContextType.EXTENDED
• Optimistic concurrency control (e.g. version, dirty properties)

Fetching – Relationships
Association FetchType
@ManyToOne EAGER
@OneToOne EAGER
@OneToMany LAZY
@ManyToMany LAZY
• LAZY associations can be fetched eagerly
• EAGER associations cannot be fetched lazily

Fetching – Best Practices
• Default to FetchType.LAZY
• Fetch directive in JPQL/Criteria API queries
• Entity graphs / @FetchProfile
• LazyInitializationException

Fetching – Open Session in View Anti-Pattern

Fetching – Temporary Session Anti-Pattern
• “Band aid” for LazyInitializationException
• One temporary Session/Connection for every lazily fetched
association
<property
name="hibernate.enable_lazy_load_no_trans"
value="true"/>

Caching

Caching – Why 2nd - Level Caching

Caching – Why 2nd - Level Caching
“There are only two hard things in Computer
Science: cache invalidation and naming things.”
Phil Karlton

Caching – Strategies
Strategy Cache type Particularity
READ_ONLY READ-THROUGH Immutable
NONSTRICT_READ_WRITE READ-THROUGH Invalidation/
Inconsistency risk
READ_WRITE WRITE-THROUGH Soft Locks
TRANSACTIONAL WRITE-THROUGH JTA

Caching – Collection Cache
• It complement entity caching
• It stores only entity identifiers
• Read-Through
• Invalidation-based (Consistency over Performance)

Caching – Aggregates

Questions and Answers
• Performance and Response Time
• Connection providers
• Identifier generators
• Relationships
• Batching
• Fetching
• Caching

High-Performance Hibernate - JDK.io 2018

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