Q:

JPA GeneratedValue generated and already existent Id

I am developing a Spring application that uses JPA.  Specifically, to generate the ids of my entities I am using the @GeneratedValue annotation.  For example:
@Entity
public class SomeEntity {
  @Id
  @GeneratedValue
  private Long id;
  
  private String someField;

  // Getters and Setters...
}

The thing is, I am preloading data into the database.  For example, in someFile.sql I have regular INSERT statements:
INSERT INTO some_entity (id, some_field) VALUES (1, 'foo');
INSERT INTO some_entity (id, some_field) VALUES (2, 'bar');
...

Then, I just insert the data using the mysql command line client:
mysql someDB < someFile.sql

The problem is, when a try to persist a new entity using JPA, the first id which will be assigned is 1.  However, that id was already being used by one of the entities I had preloaded to the database.  This way, I am getting a duplicate key error:

2020-07-04 16:08:42.365 ERROR 847 --- [https-jsse-nio-8080-exec-9] o.h.engine.jdbc.spi. SqlExceptionHelper   : Duplicate entry '1' for key 'PRIMARY'

I have considered using an initial value with a @SequenceGenerator.  However, this approach could lead to having to change the code if the ammount of initial values I want to preload increases. 
Any ideas on a different approach? 

A:

Well, the simplest solution is to make the script itself establish the correct value for the next generated id.
If you're using Hibernate <5 or Hibernate 5 with hibernate.id.new_generator_mappings=false, your setup will have resulted in id being an AUTO_INCREMENT column.  In that case simply add
ALTER TABLE some_entity AUTO_INCREMENT = <last_inserted_id>

at the end of your script.  Or, better still, try to get rid of the hardcoded id values altogether, if possible.  You can retrieve the last inserted id using LAST_INSERT_ID() and use that value for setting foreign key columns in dependent rows. 
If, on the other hand, you're using Hibernate 5 without any special config, you should find a hibernate_sequence table in your schema, which stores the next generated id to be used by Hibernate.  You will need to add sth like:
UPDATE hibernate_sequence SET next_val= <max_inserted_id_for_any_table_plus_one>

As a side note, if you're using the latter approach by accident, you might want to switch to the former.