Java & SQL Stronger Together€¦ · Java & SQL Stronger Together ... SQL Server. Database JDBC JPA Spring Data JPA Your Code SELECT a.a1, SUM(b.a1) , SUM(CASE WHEN b.a2=1 THEN b.a1

Java & SQL Stronger Together

@MarkusWinand @ModernSQL

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“We can solve any problem by introducing an extra

level of abstraction” (Based on the “fundamental theorem of software engineering”)

Database

DatabaseJDBC

Provides unique API for different SQL-

Databases

DatabaseJDBCJPA


Databases

Maps objects from/to tables

DatabaseJDBCJPA

Spring Data JPA


Databases


Makes common tasks very simple

DatabaseJDBCJPA

Spring Data JPAYour Code


Databases



DatabaseJDBCJPA



Databases

Maps Objects from/to tables


90%?

Doesn’t provide 100% of underlying

functionality

DatabaseJDBCJPA



Databases



90%?Proprietary data types? —> (VendorCls)jdbcCls

DatabaseJDBCJPA



Databases




The processing is not about objects? —> QueryBuilder, JPQL

or native queries

DatabaseJDBCJPA



Databases





or native queries

“Hibernate’s design goal is to relieve the developer

from 95% of common data persistence-related

programming tasks[…] Hibernate does not hide

the power of SQLfrom you[…]”

— Hibernate ORM User Guide (second paragraph)

DatabaseJDBCJPA



Databases





or native queries

DatabaseJDBCJPA



Databases





or native queries

findBy… not powerful enough? —> QueryBuilder, JPQL

or native queries

What is theright level of abstraction

for any given problem?

Pattern #1: Lists

1.2.3.

Go for a walk in the woods

Picnic

Improve SQL-foo

BUCKET LISTSpring

DatabaseJDBCJPA


List: All Attributes

DatabaseJDBCJPA


SELECT*FROMtbl


DatabaseJDBCJPA


ResultSetrs=c.prepareStatement("SELECT*"+"FROMtbl").executeQuery();

SELECT*FROMtbl


DatabaseJDBCJPA


Collection<Entity>c=em.createQuery("FROMEntity").getResultList();


SELECT*FROMtbl


DatabaseJDBCJPA


Collection<Entity>c=em.createQuery("FROMEntity").getResultList();

Collection<Entity>c=r.findAll();


SELECT*FROMtbl


DatabaseJDBCJPA


List: Some Attributes

DatabaseJDBCJPA


SELECTa1,…FROMtbl


DatabaseJDBCJPA


SELECTa1,…FROMtbl


Runtime improvement: ~0% - 10 000%

DatabaseJDBCJPA


SELECTa1,…FROMtbl



Affects:

DatabaseJDBCJPA


SELECTa1,…FROMtbl



Affects:- Java: GC

DatabaseJDBCJPA


SELECTa1,…FROMtbl



Affects:- Java: GC- Network

DatabaseJDBCJPA


SELECTa1,…FROMtbl



Affects:- Java: GC- Network- Database:

DatabaseJDBCJPA


SELECTa1,…FROMtbl



Affects:- Java: GC- Network- Database:

- Index Only Scan

DatabaseJDBCJPA


SELECTa1,…FROMtbl



Affects: - Java: GC - Network - Database:

- Index Only Scan - Mem + CPU (e.g. sorting)

DatabaseJDBCJPA


ResultSetrs=c.prepareStatement("SELECTa1,…"+"FROMtbl").executeQuery();

SELECTa1,…FROMtbl


DatabaseJDBCJPA


Collection<DTO>c=em.createQuery("SELECTnewDTO(a1,…)"+"FROMEnt").getResultList();


SELECTa1,…FROMtbl


DatabaseJDBCJPA




SELECTa1,…FROMtbl


Or: LAZY attributes

DatabaseJDBCJPA




SELECTa1,…FROMtbl


Or: LAZY attributes

CollectionfindAllProjectedBy(Classp);

DatabaseJDBCJPA




SELECTa1,…FROMtbl


Or: LAZY attributes

CollectionfindAllProjectedBy(Classp);

publicinterfaceProj{…getA1();…}

DatabaseJDBCJPA




SELECTa1,…FROMtbl


Or: LAZY attributes

CollectionfindAllProjectedBy(Classp);Collection<Proj>c=r.findAllProjectedBy(Proj.class);

publicinterfaceProj{…getA1();…}

DatabaseJDBCJPA


List: Attributes of Multiple Objects

DatabaseJDBCJPA


SELECTa.a1,b.a1,…FROMtblaJOINtbl2b


DatabaseJDBCJPA


Collection<DTO>c=em.createQuery("SELECT"+"newDTO(a.a1,b.a1,…)"+"FROMEntityaJOINa.childb").getResultList();



DatabaseJDBCJPA






DatabaseJDBCJPA






publicinterfaceProj{…getA1();Proj2getB();}

DatabaseJDBCJPA







Still selects all columns

DATAJPA-1218

DatabaseJDBCJPA





@Query("SELECT"+"newDTO(a.a1,b.a1,…)"+"FROMEntityaJOINa.childb")Collection<DTO>findAllDtoProj();Collection<DTO>c=r.findAllDtoProj();


Still selects all columns

DATAJPA-1218

DatabaseJDBCJPA


List: Derived Data

DatabaseJDBCJPA


SELECTa.a1,SUM(b.a1)FROMtblaJOINtbl2bGROUPBYa.a1

List: Derived Data

DatabaseJDBCJPA

Spring Data JPAYour Code Collection<DTO>c=

em.createQuery("SELECT"+"newDTO(a.a1,SUM(b.a1))"+"FROMEntityaJOINa.childb"+"GROUPBYa").getResultList();


List: Derived Data

DatabaseJDBCJPA

Spring Data JPAYour Code Collection<DTO>c=

em.createQuery("SELECT"+"newDTO(a.a1,SUM(b.a1))"+"FROMEntityaJOINa.childb"+"GROUPBYa").getResultList();


List: Derived Data@Query("SELECT"+"newDTO(a.a1,SUM(b.a1))"+"FROMEntityaJOINa.childb"+"GROUPBYa")Collection<DTO>findAllDtoProj();Collection<DTO>c=r.findAllDtoProj();

DatabaseJDBCJPA


SELECTa.a1,SUM(b.a1),SUM(CASEWHENb.a2=1THENb.a1ELSE0END)FROMtblaJOINtbl2bGROUPBYa.a1

List: Derived Data

DatabaseJDBCJPA



List: Derived Data

More beautifully, but rarely supported: SELECTa.a1,SUM(b.a1),SUM(b.a1)FILTER(WHEREb.a2=1)FROMtblaJOINtbl2bGROUPBYa.a1

DatabaseJDBCJPA



List: Derived Data


1999

2001

2003

2005

2007

2009

2011

2013

2015

2017

2019

5.1 MariaDBMySQL

9.4 PostgreSQL1.0 3.30 SQLite

DB2 LUWOracleSQL Server

DatabaseJDBCJPA



List: Derived Data

JPQL doesn't allow CASE in aggregates


1999

2001

2003

2005

2007

2009

2011

2013

2015

2017

2019

5.1 MariaDBMySQL

9.4 PostgreSQL1.0 3.30 SQLite

DB2 LUWOracleSQL Server

DatabaseJDBCJPA



List: Derived Data


DatabaseJDBCJPA



List: Derived Data@NamedNativeQuery(name="Entity.findAllXy",query="<<SQL>>",resultSetMapping="…")@SqlResultSetMapping(…)publicclassEntity{…}


DatabaseJDBCJPA




Collection<DTO>c=em.createNamedQuery("Entity.findAllXy").getResultList();


DatabaseJDBCJPA




Collection<DTO>c=em.createNamedQuery("Entity.findAllXy").getResultList();

@Query(native=true)Collection<DTO>findAllXy();


Application

Application

Application

Application ORMs are super useful for the Load-Change-Store

cycle on complexentity graphs.

Application ORMs are super useful for the Load-Change-Store

cycle on complexentity graphs.

If the cycle is broken,entities might not be the right level of abstraction.

Pattern #2: Search

Pattern #2: Search

DatabaseJDBCJPA


SELECT*FROMtbla<<supercomplexquery>>

Search: Load Entity from Native Query

DatabaseJDBCJPA




@NamedNativeQuery(name="Entity.findSpecialOnes",query="<<SQL>>",resultSetMapping="…")@SqlResultSetMapping(@entities=@EntityResult(entityClass=Entity.class))publicclassEntity{…}

DatabaseJDBCJPA





@Query(native=true)Collection<Entity>findSpecialOnes();

CREATETABLEt(idINTEGER,parentINTEGER,)



publicvoiddescendTree(Entitystart){for(Entitye:start.getChildren()){descendTree(e);}}



SELECT...FROMEntityWHEREparent=?







publicvoidascendTree(Entitye){while(e!=null){e=e.getParent();}}




SELECT...FROMEntityWHEREid=?

SELECTt.id,t.parentFROMtWHEREt.id=?

SELECTt.id,t.parentFROMtWHEREt.id=?UNIONALLSELECTt.id,t.parentFROMtWHEREt.parent=?



WITHRECURSIVEprev(id,parent)AS(

)

SELECTt.id,t.parentFROMtWHEREt.id=?UNIONALLSELECTt.id,t.parentFROMtJOINprevONt.parent=prev.id

SELECT*FROMprev


)

SELECTt.id,t.parentFROMtWHEREt.id=?UNIONALLSELECTt.id,t.parentFROMtJOINprevONt.parent=prev.id

SELECT*FROMprev


)

SELECTt.id,t.parentFROMtWHEREt.id=?UNIONALLSELECTt.id,t.parentFROMtJOINprevONprev.parent=t.id

SELECT*FROMprev

Vendor Dialect

Vendor DialectStandard SQL (ISO 9075)


HQL


HQLJPQL


HQLJPQL

Spring .findBy…


HQLJPQL

Spring .findBy…

1999

2001

2003

2005

2007

2009

2011

2013

2015

2017

2019

5.1 10.2 MariaDB8.0 MySQL

8.4 PostgreSQL1.0 3.8.3 SQLite

7.0 DB2 LUW11gR2 Oracle

2005 SQL Server

* without keyword recursive

withrecursive

**

*

JVM

JVM

JVM


JVM


JVM


JVM


PersistenceContext

JVM


PersistenceContext

JVM


PersistenceContext

JVM


PersistenceContext

What if I run the recursive query



before my JPA logic?

JVM

PersistenceContext

JVM

PersistenceContext


JVM

PersistenceContext

findSpecialOnes();//WarmUp

JVM

PersistenceContext


JVM

PersistenceContext


JVM


PersistenceContext


A lot has happened

since SQL-92

SQL has evolved

beyond the relational idea

A lot has happened

since SQL-92

SQL has evolved


If you use SQL for CRUD operations only, you are doing it wrong

A lot has happened

since SQL-92

SQL has evolved


If you use SQL for CRUD operations only, you are doing it wrong

A lot has happened

since SQL-92

https://modern-sql.com @ModernSQL by @MarkusWinand

Documents

Java & SQL Stronger Together€¦ · Java & SQL Stronger Together ... SQL Server. Database JDBC JPA Spring Data JPA Your Code SELECT a.a1, SUM(b.a1) , SUM(CASE WHEN b.a2=1 THEN b.a1