This document discusses database performance optimization techniques when using Hibernate. It covers topics like connection management, identifier generation strategies, batching, fetching strategies, caching. The key message is that database access time consists of several components like connection acquisition, data access logic, statement submission/execution, result fetching. Optimizing these areas can significantly improve performance.

1. #DevoxxFR

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• Hibernate Developer Advocate
• vladmihalcea.com
• @vlad_mihalcea

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

4. #DevoxxFR
• Connection acquisition time
• Data access logic (e.g. entity state transitions)
• Statements submission time
• Statements execution time
• Result set fetching time
• Idle time prior to releasing the database connection
𝑇 = 𝑡 𝑎𝑐𝑞 + 𝑡 𝑑𝑎𝑙 + 𝑡 𝑟𝑒𝑞 + 𝑡 𝑒𝑥𝑒𝑐 + 𝑡 𝑟𝑒𝑠 + 𝑡𝑖𝑑𝑙𝑒

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• Connection providers
• Identifier generators
• Relationships
• Batching
• Fetching
• Caching

6. #DevoxxFR

7. #DevoxxFR
𝑇 = 𝑡 𝑎𝑐𝑞 + 𝑡 𝑑𝑎𝑙 + 𝑡 𝑟𝑒𝑞 + 𝑡 𝑒𝑥𝑒𝑐 + 𝑡 𝑟𝑒𝑠 + 𝑡𝑖𝑑𝑙𝑒

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• Connections acquired lazily
• The shorter the transaction lifespan, the higher the transaction
throughput

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10 50 100 500 1000 5000 10000
0
200
400
600
800
1000
1200
1400
Statement count
Time(ms)
After statement After transaction

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<property name="hibernate.connection.release_mode" value="after_transaction"/>
• For JTA (e.g. Java EE), try this setting:

12. #DevoxxFR
• AUTO (IDENTITY or SEQUENCE)
• IDENTITY
• SEQUENCE
• TABLE
𝑇 = 𝑡 𝑎𝑐𝑞 + 𝑡 𝑑𝑎𝑙 + 𝑡 𝑟𝑒𝑞 + 𝑡 𝑒𝑥𝑒𝑐 + 𝑡 𝑟𝑒𝑠 + 𝑡𝑖𝑑𝑙𝑒

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• Default for SQL Server and MySQL when using AUTO
• Disables JDBC batch inserts

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• Default for Oracle and PostgreSQL when using AUTO
• May use roundtrip optimizers: hi/lo, pooled, pooled-lo
• Hibernate 5 uses the enhanced sequence generator by default
<property name="hibernate.id.new_generator_mappings" value="true"/>

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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)

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

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1 5 10 50
0
0.5
1
1.5
2
2.5
3
Table increment size
Time(ms)

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• Identity makes no use of batch inserts
• Table generator using an increment size of 100

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1 2 4 8 16
0
500
1000
1500
2000
2500
Thread count
Time(ms)
Identity Table

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• Both generators use an increment size of 100
1 2 4 8 16
0
200
400
600
800
1000
1200
Thread count
Time(ms)
Sequence Table

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𝑇 = 𝑡 𝑎𝑐𝑞 + 𝑡 𝑑𝑎𝑙 + 𝑡 𝑟𝑒𝑞 + 𝑡 𝑒𝑥𝑒𝑐 + 𝑡 𝑟𝑒𝑠 + 𝑡𝑖𝑑𝑙𝑒

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<property name="hibernate.jdbc.batch_size" value="10"/>
• SessionFactory configuration
• Plan to support Session-level batch size configuration
𝑇 = 𝑡 𝑎𝑐𝑞 + 𝑡 𝑑𝑎𝑙 + 𝑡 𝑟𝑒𝑞 + 𝑡 𝑒𝑥𝑒𝑐 + 𝑡 𝑟𝑒𝑠 + 𝑡𝑖𝑑𝑙𝑒

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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

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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

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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

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<property name="hibernate.order_inserts" value="true"/>
<property name="hibernate.order_updates" value="true"/>
• Plan to support delete statement ordering too

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

28. #DevoxxFR
• JDBC fetch size
• JDBC ResultSet size
• DTO vs Entity queries
• Association fetching
𝑇 = 𝑡 𝑎𝑐𝑞 + 𝑡 𝑑𝑎𝑙 + 𝑡 𝑟𝑒𝑞 + 𝑡 𝑒𝑥𝑒𝑐 + 𝑡 𝑟𝑒𝑠 + 𝑡𝑖𝑑𝑙𝑒

29. #DevoxxFR
• 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"/>

30. #DevoxxFR
• Query-level fetch size setting
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();

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1 10 100 1000 10000
0
100
200
300
400
500
600
Fetch size
Time(ms)
DB_A DB_B DB_C DB_D

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• Hibernate SQL-level limiting (works for native queries too!)
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();

33. #DevoxxFR
• 100k Post(s) and + 1M PostComment(s) vs 100 entries
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

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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
• Selecting all columns vs selecting a custom projection

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• 100 Post(s), 100 PostDetail(s) , and 1000 PostComment(s)
All columns Custom projection
0
5
10
15
20
25
30
Time(ms)
DB_A DB_B DB_C DB_D

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

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

38. #DevoxxFR

39. #DevoxxFR
“You can turn a Lazy into an
Eager, but you cannot turn an
Eager into a Lazy”

40. #DevoxxFR
• Default to FetchType.LAZY
• Fetch directive in JPQL/Criteria API queries
• Entity graphs / @FetchProfile
• LazyInitializationException

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

43. #DevoxxFR
𝑇 = 𝑡 𝑎𝑐𝑞 + 𝑡 𝑑𝑎𝑙 + 𝑡 𝑟𝑒𝑞 + 𝑡 𝑒𝑥𝑒𝑐 + 𝑡 𝑟𝑒𝑠 + 𝑡𝑖𝑑𝑙𝑒

44. #DevoxxFR

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“There are only two hard things in
Computer Science: cache
invalidation and naming things.”
Phil Karlton

46. #DevoxxFR

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• Complement entity caching
• Store only entity identifiers
• Read-Through
• Invalidation-based (Consistency over Performance)

48. #DevoxxFR

49. #DevoxxFR
https://leanpub.com/high-performance-java-persistence
𝑇 = 𝑡 𝑎𝑐𝑞 + 𝑡 𝑑𝑎𝑙 + 𝑡 𝑟𝑒𝑞 + 𝑡 𝑒𝑥𝑒𝑐 + 𝑡 𝑟𝑒𝑠 + 𝑡𝑖𝑑𝑙𝑒