Question

I am using Hibernate Envers to audit some entities. I manually created the associated audit tables. However, I am having trouble determining what an audit table’s primary key should be. For example, consider a fictional table designed to store customers:

CREATE TABLE CUSTOMER
(
    CUSTOMER_ID   INTEGER,
    CUSTOMER_NAME VARCHAR(100),

    PRIMARY KEY (CUSTOMER_ID)
)

And you create the audit table:

CREATE TABLE CUSTOMER_REVISION
(
    REVISION_ID      INTEGER,
    REVISION_TYPE_ID INTEGER,
    CUSTOMER_ID      INTEGER,
    CUSTOMER_NAME    VARCHAR(100),

    PRIMARY KEY (???)
)

Here were the options I considered:

Primary key: REVISION_ID

This cannot be the primary key because multiple entities of the same class may be modified during the same revision.

Primary key: (REVISION_ID, CUSTOMER_ID)

This seems more likely, but I’m not sure if Envers will insert multiple records per customer per revision.

Primary key: (REVISION_ID, REVISION_TYPE_ID, CUSTOMER_ID)

This seems like overkill, but it may be possible that Envers will insert different types of records (add, modify or delete) per customer per revision.

Primary key: A new column

Perhaps the primary key must simply be another column containing a synthetic primary key.

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What is the true primary key of an audit table managed by Hibernate Envers?

Answer 1

Judging by the examples in the documentation, it appears that the primary key in my example would be (REVISION_ID, CUSTOMER_ID). Here is the example in the documentation:

create table Address (
    id integer generated by default as identity (start with 1),
    flatNumber integer,
    houseNumber integer,
    streetName varchar(255),
    primary key (id)
);

create table Address_AUD (
    id integer not null,
    REV integer not null,
    flatNumber integer,
    houseNumber integer,
    streetName varchar(255),
    REVTYPE tinyint,
    ***primary key (id, REV)***
);