I use Spring Boot 2 and Spring data jpa (Hibernate 5.2.1) to work with the database.
I use Postgresql.
In the database I created a sequence
create sequence USERS_SEQ cache 5
and created entity
#Entity
#Table(name = "users")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "USERS_SEQ")
#SequenceGenerator(name = "USERS_SEQ", sequenceName = "USERS_SEQ", allocatedSize = 1)
private Long id;
}
I assumed that the numbers from the sequence would be given to me sequentially: 1,2, 3 and so on, even if I restart the application. But after restarting, hibernate assigns values to the records with an offset of 5, that is, the first start:1, the second restart:6, the third restart:11. As far as I understand, this is because of the cache property.
At the same time, if I run select nextval('USERS_SEQ') in db after the second restart, I will get not 7, but 2, that is, the next number after 1
How can I avoid this? I have two instances of the application and I'm afraid that the ids will overlap
Related
I'm inserting data into Postgres database, here is my Entity:
public class FileData {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id", nullable = false)
private Long id;
}
with intellJ idea auto generated repository interface:
fileDataRepository.save(fileData);
I was able to insert data into my database fine, until the Id number goes to the current value of 152560, then every time I try to insert a line of data, I get the following error:
PSQLException: ERROR: duplicate key value violates unique constraint "file_data_pkey"
Detail: Key (id)=(53) already exists.
I confirmed that the fileData I constructed have null for it's id value, and everytime I call the save(or saveAndFlush), the duplicate key value increases, seems to me that JPA have somehow decided to reset the counter on this table.
So my question is, it's there a limit to the number generated by JPA? And is there a way to configure it?
The only limitation is the database datatype.
But, you shouldn't use #GeneratedValue(strategy = GenerationType.AUTO) because it's not clear how the id will be generated. Hibernate will try to figure that out by itself.
As you are using Postgresql you should go with a Sequence like this:
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "filedata_seq")
#SequenceGenerator(name = "filedata_seq")
Read more about https://vladmihalcea.com/jpa-entity-identifier-sequence/
We use a dockerized postgres database and have hibernate auto-generate the tables (using spring.jpa.hibernate.ddl-auto: create) for our integration tests. Using something like H2 is not an option because we do some database-specific operations in a few places, e.g. native SQL queries.
Is there any way to avoid id collisions when all entities use auto-incremented ids? Either by offsetting the start id or, better yet, having all tables use a shared sequence?
Schema is created when the docker container is launched, tables are created by Spring Data JPA/Hibernate
Example
Examples use kotlin syntax and assumes the "allopen"-plugin is applied for entities.
Sometimes we've had bugs where the wrong foreign key was used, e.g. something like this:
#Entity
class EntityOne(
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id", nullable = false, columnDefinition = "SERIAL")
var id: Long,
)
#Entity
class EntityTwo(
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id", nullable = false, columnDefinition = "SERIAL")
var id: Long,
)
#Entity
class JoinEntity(
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id", nullable = false, columnDefinition = "SERIAL")
var id: Long,
#ManyToOne
#JoinColumn(name = "entity_one_id")
var entityOne: EntityOne,
#ManyToOne
#JoinColumn(name = "entity_two_id")
var entityTwo: EntityTwo,
)
#Repository
interface JoinEntityRepository : JpaRepository<JoinEntity, Long> {
//
// Bug here! Should be "WHERE entityOne.id = :entityOneId"
//
#Query("SELECT entityTwo FROM JoinEntity WHERE entityTwo.id = :entityOneId")
fun findEntityTwoByEntityOneId(entityOneId: Long): Collection<EntityTwo>
}
These bugs can in some circumstances be very hard to find because when the table is created, there may very well be an Entity2 with the same id as some Entity1, and so the query succeeds but the test fails somewhere down the line because while it is returning one or more Entity2, it's not the expected ones.
Even worse, depending on the scope of the test it may pass even if the wrong entity is fetched, or fail only when tests are run in a specific order (due to ids getting "out of sync"). So ideally it should fail to even find an entity when the wrong id is passed. But because the database structure is created from scratch and the ids are auto-incremented they always start at 1.
I found a solution to this.
In my resources/application.yml (in the test folder, you most likely do not want to do this in your main folder) I add spring.datasource.initialization-mode: always and a file data.sql.
The contents of data.sql are as follows:
DROP SEQUENCE IF EXISTS test_shared_sequence;
CREATE SEQUENCE test_shared_sequence;
ALTER TABLE entity_one ALTER COLUMN id SET DEFAULT nextval('test_shared_sequence');
ALTER TABLE entity_two ALTER COLUMN id SET DEFAULT nextval('test_shared_sequence');
After Spring has auto-generated the tables (using spring.jpa.hibernate.ddl-auto: create) it will run whatever is in this script, and the script will change all tables to auto-generate ids based on the same sequence, meaning that no two entities will ever have the same id regardless of which table they're stored in, and as such any query that looks in the wrong table for an id will fail consistently.
I am using Spring data JPA to persist data into PostgreSQL. I have an entity called 'Game' in which Id is primary key and it's auto generated value which gets incremented by '1'. I have another column 'game_code' which accepts only unique values.
Whenevr i tried to persist entity with gamecode value which is already exists in the table. it gives an error. which is corret. But, the value of the ID is getting skipped. Please find the below example.
#Entity
#Table(name = "game")
#Data
public class Game {
#Id
#SequenceGenerator(name = "GAME_SEQ", sequenceName = "GAME_SEQ", allocationSize = 1)
#GeneratedValue(strategy = GenerationType.AUTO, generator = "GAME_SEQ")
#Column(updatable = false, nullable = false)
private Integer id;
#Column(nullable = false)
private String gameName;
#Column(nullable = false , unique=true)
private String gameCode;
}
gameRepo.save(new Game("game_name_1","game_code_1")) --> it saves entity in DB with ID value as 1
gameRepo.save(new Game("game_name_2","game_code_2")) --> it saves entity in DB with ID value as 2
gameRepo.save(new Game("game_name_3","game_code_2")) --> save failed as 'game_code_2' already exists
gameRepo.save(new Game("game_name_3","game_code_3")) --> it saves entity in DB with ID value as 4 .
**Here I am expecting ID value should be 3 as previous one was not saved**.
Could anyone please let me know how to overcome this issue.
Thanks,
Madhu.
I have a process in application where we insert 1000+ records in application. There is a attribute in the table as mentioned below.
#Index(name = "_IDX_UNIQUE_UUID", columnNames = {"UUID"})
#Column(name = "UUID", nullable = false)
private Long uuid;
During populating the entity class the value is set as following
entity.setUuid(service.getNextUuid());
which calls this method in service class:
public Long getNextUuid() {
Query query = entityManager.createNativeQuery("select nextval('seq_xxxx_uuid')");
//This takes lot of time to execute
Obj result = query.getSingleResult();
return ((BigInteger) result).longValue();
}
To get next value from sequence, it takes around 200-700 ms. This accumulates to several minutes if I try to insert 1000+ records. Moreover, the query is quite simple and executes in less than 1ms if I execute it in a database client.
I am using postgresql 9.4-1206-jdbc4, hibernate 4.2.0.Final and Spring 4.2.5.
It's slow, because you're going through all the layers of security and consistency checks of a JPA full query, plus you're creating a new NativeQuery object every time and not doing it though a #NamedNativeQuery, thus taking even more time to evaluate.
The solution is to annotate the column with:
#Id
#Index(name = "_IDX_UNIQUE_UUID", columnNames = {"UUID"})
#SequenceGenerator(name = "seq_xxxx_uuid_gen", sequenceName = "seq_xxxx_uuid", allocationSize = 1)
#GeneratedValue(generator = "seq_xxxx_uuid_gen")
#Column(name = "UUID", nullable = false)
private Long id;
You do want that allocationSize to be the same value as the increment_by value of your sequence, or you'll have other problems after the first persist.
If you need to use that Id for multiple objects (say it's part of a composite key, but only part of it is serial-generated), just grab it from the first one after persisting it.
Edit:
Alternatively you can forego the SequenceGenerator and use this:
#GeneratedValue(strategy = GenerationType.IDENTITY)
It may be faster, if the generated query is properly optimized and uses java.sql.Statement.getGeneratedKeys() upon insert.
I have an entity
#Entity
public class Book {
#Id
#Column(name = "book_id")
#SequenceGenerator(name = "book_book_id_seq", sequenceName = "book_book_id_seq", allocationSize = 1)
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "book_book_id_seq")
private Long id;
// getter, setter & other fields
}
with schema
CREATE TABLE book
(
book_id bigint NOT NULL DEFAULT nextval('book_book_id_seq'::regclass),
CONSTRAINT book_pkey PRIMARY KEY (book_id)
)
What I want to achieve is sometime I would like to use sequence/id generated by database, but sometime the data is created at other place and I would like to create with existing (manual) id.
I can't set the id manually with Spring Data JPA way (using CrudRepository) or JPA way (using EntityManager), but no issue with native query. Is this JPA limitation? Any workaround for my issue?
Book book01 = new Book();
bookRepo.save(book01); // Book with id 1 is created
Book book02 = new Book();
book02.setId(5555L);
bookRepo.save(book02); // Does not create book with id 5555, but 2
Query nativeQuery = entityManager.createNativeQuery("INSERT INTO book VALUES (6666);");
nativeQuery.executeUpdate(); // Book with id 6666 is created
Query nativeQuery02 = entityManager.createNativeQuery("INSERT INTO book DEFAULT VALUES;");
nativeQuery02.executeUpdate(); // Book with id 3 is created
I am using PostgreSQL 9.4, Hibernate 5 and Java 8.
On persist, if a field is annotated with #GeneratedValue, it will generate the ID with whatever strategy is specified. Then it will set value of the id field with the generated value. So if the id is manually set using setId() before persisting, this will just be overriden.
If you want, you can use em.persist for auto-generated IDs. Then use native SQL for manually setting the Id, since native SQLs will bypass whatever mapping you have on your entity.
Yes, by default Hibernate org.hibernate.id.SequenceGenerator always generate new id. What you should do is to override public Serializable generate(SessionImplementor session, Object obj) method, where if your obj (cast to your entity first) has id, then return the id, else get it from database sequence.