HIbernate 5: generator class=“sequence” not workin

问题:

I have following mapping:

    <id name="id" type="java.lang.Long" column="id">
        <generator class="sequence">
            <param name="sequence">tracksdata_seq</param>
        </generator>
    </id>

Everything went fine when I worked with it in Hibernate 4.2. Now I am migrating to Hibernate 5 and facing following issue:

2015-10-06 19:49:50 DEBUG SQL:92 - select nextval ('hibernate_sequence')
2015-10-06 19:49:50 DEBUG SqlExceptionHelper:122 - could not extract ResultSet [n/a]
org.postgresql.util.PSQLException: ERROR: relation "hibernate_sequence" does not exist

How to resolve this issue?

P.S. Hibernate 5.0.2.Final.

回答1:

You have two options:

1. You set the hibernate.id.new_generator_mappings configuration property to false and switch back to the old identifier generators

2. You change the mapping as follows, from this:

   <generator class="sequence">
       <param name="sequence">MY_SEQUENCE</param>
   </generator>
   

   to:

   <generator class="org.hibernate.id.enhanced.SequenceStyleGenerator">
       <param name="optimizer">none</param>
       <param name="increment_size">1</param>
       <param name="sequence_name">MY_SEQUENCE</param>
   </generator>
   

回答2:

I also encountered this problem when migrating from Hibernate 4.3.10 to Hibernate 5.0.4. Like maksim2020, I replaced instances of <generator class="sequence"> with <generator class="identity">. However, to preserve the id sequence for the affected tables I also had to write a sql migration script which set the default value for the column to be the next value of the existing sequence. In PostgreSQL this is done as follows:

ALTER TABLE ONLY affected_table ALTER COLUMN affected_id SET DEFAULT nextval('original_sequence'::regclass);

回答3:

Use "sequence_name" instead of "sequence" in <param name="sequence">.

That worked for me.