Как настроить предложение о присоединении к ассоциации сущностей с помощью Hibernate @JoinFormula

CREATE TABLE Account (
    id int8 NOT NULL ,
    credit float8 ,
    locale VARCHAR(255) ,
    rate float8 ,
    PRIMARY KEY (id)
)

@Entity(name = "Account")
public class Account {

    @Id
    private Long id;

    private Double credit;

    private Double rate;

    private Locale locale;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinFormula(
        "REGEXP_REPLACE(locale, '\\w+_(\\w+)[_]?', 
        '\\1')" 
    )
    private Country country;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinFormula(
        "REGEXP_REPLACE(locale, '(\\w+)_.*', 
        '\\1')"
    )
    private Language language;

    //Getters and setters omitted for brevity
}

Country _US = new Country();
_US.setId( "US" );
_US.setName( "United States" );
_US.setVatRate(0.1);

Country _UK = new Country();
_UK.setId( "UK" );
_UK.setName( "United Kingdom" );
_UK.setVatRate(0.2);

Country _Spain = new Country();
_Spain.setId( "ES" );
_Spain.setName( "Spain" );
_Spain.setVatRate(0.21);

Country _Mexico = new Country();
_Mexico.setId( "MX" );
_Mexico.setName( "Mexico" );
_Mexico.setVatRate(0.16);

Language _English = new Language();
_English.setId( "en" );
_English.setName( "English" );

Language _Spanish = new Language();
_Spanish.setId( "es" );
_Spanish.setName( "Spanish" );

doInJPA( entityManager -> {
    entityManager.persist( _US );
    entityManager.persist( _UK );
    entityManager.persist( _Spain );
    entityManager.persist( _Mexico );
    entityManager.persist( _English );
    entityManager.persist( _Spanish );
} );

doInJPA( entityManager -> {
    Account account1 = new Account( );
    account1.setId( 1L );
    account1.setCredit( 5000d );
    account1.setRate( 1.25 / 100 );
    account1.setLocale( Locale.US );
    entityManager.persist( account1 );

    Account account2 = new Account( );
    account2.setId( 2L );
    account2.setCredit( 200d );
    account2.setRate( 1.25 / 100 );
    account2.setLocale( new Locale( "es", "MX" ) );
    entityManager.persist( account2 );
} );

doInJPA( entityManager -> {
    LOGGER.info("Fetch first Account");
    Account account1 = entityManager.find( 
        Account.class, 1L 
    );
    assertEquals( _English, account1.getLanguage());
    assertEquals( _US, account1.getCountry());

    LOGGER.info("Fetch second Account");
    Account account2 = entityManager.find( 
        Account.class, 2L 
    );
    assertEquals( _Spanish, account2.getLanguage());
    assertEquals( _Mexico, account2.getCountry());
} );

-- Fetch first Account

SELECT a.id AS id1_0_0_,
       a.credit AS credit2_0_0_,
       a.locale AS locale3_0_0_,
       a.rate AS rate4_0_0_,
       REGEXP_REPLACE(
           a.locale, 
           'w+_(w+)[_]?', 
           '\1'
       ) AS formula2_0_,
       REGEXP_REPLACE(
           a.locale, 
           '(w+)_.*', 
           '\1'
       ) AS formula3_0_
FROM   Account a
WHERE  a.id = 1

SELECT l.id AS id1_2_0_,
       l.name AS name2_2_0_
FROM   Language l
WHERE  l.id = 'en'

SELECT c.id AS id1_1_0_,
       c.name AS name2_1_0_,
       c.vatRate AS vatRate3_1_0_
FROM   Country c
WHERE  c.id = 'US'

-- Fetch second Account

SELECT a.id AS id1_0_0_,
       a.credit AS credit2_0_0_,
       a.locale AS locale3_0_0_,
       a.rate AS rate4_0_0_,
       REGEXP_REPLACE(
           a.locale, 
           'w+_(w+)[_]?', 
           '\1'
       ) AS formula2_0_,
       REGEXP_REPLACE(
           a.locale, 
           '(w+)_.*', 
           '\1'
       ) AS formula3_0_
FROM   Account a
WHERE  a.id = 2

SELECT l.id AS id1_2_0_,
       l.name AS name2_2_0_
FROM   Language l
WHERE  l.id = 'es'

SELECT c.id AS id1_1_0_,
       c.name AS name2_1_0_,
       c.vatRate AS vatRate3_1_0_
FROM   Country c
WHERE  c.id = 'MX'

Account account1 = entityManager.createQuery(
    "select a " +
    "from Account a " +
    "join a.language l " +
    "join a.country c " +
    "where a.id = :accountId", Account.class )
.setParameter("accountId", 1L)
.getSingleResult();

assertEquals( _English, account1.getLanguage());
assertEquals( _US, account1.getCountry());

SELECT a.id                                            AS id1_0_, 
       a.credit                                        AS credit2_0_, 
       a.locale                                        AS locale3_0_, 
       a.rate                                          AS rate4_0_, 
       REGEXP_REPLACE(a.locale, '\w+_(\w+)[_]?', '\1') AS formula2_, 
       REGEXP_REPLACE(a.locale, '(\w+)_.*', '\1')      AS formula3_ 
FROM   Account a 
INNER JOIN 
       Language l 
ON REGEXP_REPLACE(a.locale, '(\w+)_.*', '\1') = l.id 
INNER JOIN 
       Country c 
ON REGEXP_REPLACE(a.locale, '\w+_(\w+)[_]?', '\1') = c.id 
WHERE  a.id = 1 

CREATE INDEX account_language_idx 
ON Account (REGEXP_REPLACE(locale, '(\w+)_.*', '\1'));

CREATE INDEX account_country_idx 
ON Account (REGEXP_REPLACE(locale, '\w+_(\w+)[_]?', '\1'));