Cfrgtkky

I want one of the fields to be ignored when called save() method. The field is gonna get populated automatically by the database and returned. It should be treated as a read-only field.

I am concerned about private Timestamp ts; field:

@Entity

@Table(name = "time_series", schema = "ms")

@IdClass(Reading.class)

public class Reading implements Serializable {



   private static final long serialVersionUID = 1L;



   @Id

   @Column(name = "name", nullable = false)

   private String sensorName;



   @Id

   @Column(name = "ts", insertable = false, updatable = false)

   private Timestamp ts;



   @Column(name = "reading")

   private Double value;

   ...

As you see, I use insertable = false, updatable = false are inside the @Column annotation, so I'd expect that ts is ignored when forming the actual SQL behind the curtain.

@Override

@Transactional(readOnly = false)

public Reading save(Reading r) {        

    return readingRepository.save(r);

}

ReadingRepository is basically extended Spring's CrudRepository which has save(...) method.

When I save Reading object with ts=null I get an error from Postgres:

ERROR: null value in column "ts" violates not-null constraint

because Spring Data did not actually ignore the ts field based what I see from the log:

insert into ms.time_series (ts, name, reading) values (NULL, 'sensor1', 10.0)

Clearly, I want the query to be without ts like this:

insert into ms.time_series (name, reading) values ('sensor1', 10.0)

Why is the field not being ignored?

Now if you ask me whether my database schema is okay I say yes. When I type SQL query in console without the ts everything is fine. I even tried @Generated and @GeneratedValue annotations. Name and ts are both forming a primary key for the table, however, the result is the same if I make only one of them a PK or if I add an extra surrogate ID column. Same result...

Am I overlooking something or is there maybe a bug in the Spring framework?? I am using Spring 5.1.2 and SpringData 2.1.2

Note: If I use @Transient annotation that persists the insert query correctly but then the field is being ignored completely even on read/fetch.

Many thanks for any help with this!

Try using GenericGenerator and GeneratedValue in your code.

Add the needed annotation and give values to all other members in Reading class, except ts.

Here some examples.

As you say

I get an error from Postgres

If you check the docs it states:

Technically, a primary key constraint is simply a combination of a unique constraint and a not-null constraint.

That's also true for multi-column primary keys (see here)

So, if ts is part of your primary key in the database (as the @Id indicates) it's simply not possible to insert null values in that column.

IMO Hibernate/Spring got nothing to do with that as

insert into ms.time_series (ts, name, reading) values (NULL, 'sensor1', 10.0)

should be equivalent to

insert into ms.time_series (name, reading) values ('sensor1', 10.0)