How is hibernate_unique_key table created in a new database?

Question

I'm trying to create my first test application with NHibernate following example in NHibernate 2.0 Beginners Guide. The example is using HiLo POID generator in mappings. I understand that this algorithm requires special database table to store current Hi value. But I don't understand how is this table created? Do I need to create table manually (I haven't found SQL script for this table) or should it be crated automatically by the session?

My current code is throwing exception with message: Invalid object name 'hibernate_unique_key' and table doesn't exist in my database.

score 8 · Accepted Answer · answered Dec 29 '10 at 19:58

8

I suggest a hilo per table strategy, to do this you will need to create the table manually and then add some rows of data e.g.

CREATE TABLE hibernate_unique_key (
  TableName varchar(25) NOT NULL,
  NextHi bigint NOT NULL
)

then add a row into the database for every table you wish to use the hilo for: e.g.

CmsLogin,10
Address, 10

Your mappings would then contain the following:-

    <id name="Id" column="Id" unsaved-value="0">
        <generator class="hilo">
            <param name="column">NextHi</param>
            <param name="where">TableName='CmsLogin'</param>
            <param name="max_lo">100</param>
        </generator>
    </id>

and viola!

answered Dec 29 '10 at 19:58

Rippo

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Thanks, it was exactly the part which the book is missing. – Ladislav Mrnka Dec 31 '10 at 12:53
No problems, glad to be of help. – Rippo Dec 31 '10 at 14:44
I have followed your advice but still have the same result: next_hi value is the same for all tables in each row. – Kimi Aug 08 '11 at 11:06
1

To use this approach with FluentNHibernate, see this good introduction post: http://www.philliphaydon.com/2010/10/using-hilo-with-fluentnhibernate/ – Alric Jan 30 '12 at 17:26

score 1 · Answer 2 · edited May 23 '17 at 11:54

1

The simpliest option how to generate database schema is to use the tool hbm2ddl: it is just the matter of configuring session factory:

<property name="hbm2ddl.auto">create</property>

Another option which I found recently is running shema export from the code. Here are details in another thread.

edited May 23 '17 at 11:54

Community

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answered Dec 30 '10 at 21:24

Petr Kozelek

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I don't need to generate the whole database. I already have the empty database and I want to use HiLo POID generator. – Ladislav Mrnka Dec 31 '10 at 12:54

How is hibernate_unique_key table created in a new database?

2 Answers2

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