@Index annotation leads to "This annotation is not applicable to target 'member property with backing field'"

Question

I am trying to create an index on a foreign key using the @Index annotation. Unfortunately, the compiler complains with the following message:

This annotation is not applicable to target 'member property with backing field'

What am I doing wrong here?

@Entity
@Table(name = "my_entity")
class MyEntity(someValue: Long) : BaseEntity(someValue) {

    // .. some fields
    
    @OneToOne
    @JoinColumn(name = "another_entity")
    @Index(name = "ix_another_entity")
    var anotherEntity: AnotherEntity? = null
}

fladdimir · Accepted Answer · 2022-02-05T11:13:38.903

1

The @Index cannot be used like this (neither in java nor in kotlin), instead you can use it e.g. as part of the @Table annotation:

@Table(name= "my_entity", indexes = [ Index(columnList = "another_entity") ])

Specifying an Index (Non-Unique Key) Using JPA

(note that e.g. MySQL auto creates an index for foreign keys: Does MySQL index foreign key columns automatically? )

edited Feb 05 '22 at 11:13

answered Feb 03 '22 at 19:50

fladdimir

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Thanks for replying. Unfortunately, this didn't work. Now the compiler complains with: `An annotation can't be used as the annotations argument`. Any idea? – Matthias Güntert Feb 04 '22 at 09:03
this looks like a kotlin specific issue, annotation arguments must not have the leading @; https://stackoverflow.com/a/62113971 – fladdimir Feb 04 '22 at 10:05
Been there, done that, did not work! `An annotation argument must be a compile-time constant` – Matthias Güntert Feb 04 '22 at 10:08
how exactly does your complete @Table annotation look like? – fladdimir Feb 04 '22 at 10:11
`@Table(name = "my_entity", indexes = { Index(columnList = "another_entity") })` – Matthias Güntert Feb 04 '22 at 10:14
1

pleasy try with the array literal syntax: `indexes = [ Index(columnList="anotherEntity") ]` – fladdimir Feb 05 '22 at 11:13

@Index annotation leads to "This annotation is not applicable to target 'member property with backing field'"

1 Answers1