Does hibernate support row level or table level locking?????
I using "WAP T" as a testing tool to test a test case scenario wuth HIBERNATE 2.1.6 and MYSQL 4.0 as database. The scenario is that 10 simultaneous users are trying to insert 100 records each. I am having servlet where i have a loop from 1 to 100, to insert records in the database. I have set the primary key id to auto increment in the hbm.xml file.

On running this test case some records are inserted and then after that there is an runtime exception that "u r trying to insert multiple records for the id <id no.>".

This means, suppose when user 1 and user 2 come simultaneously to obtain connection to database and after that user 1 has inserted 20 records and after that when user 2 tries to insert records, the count starts from 1 bcoz it was having the info that database has no records.

I tried the same scenario by removing the primary key constraint on id and it went absoulutely fine. It inserted 1000 records in the database but the id field was having multiple values....

So I concluded that either MYSQL or HIBERANTE does support the LOCKING mechanism....

Can any one comment on this conclusion. If locking mechanism is not there with HIBERNATE or MYSQL then how should i handle the situation.

Thanks........

Plz. Comment

What was the generator on your mapping? Some generators are specifically documented as not handling concurrency very well. Try switching the generator to something like sequence.

Hi eg344,

I am using the mapping something like this:

<id name="id" type="long" column="uid" unsaved-value="0">
<generator class="increment">
</generator>
</id>

The generator here is "increment".

In the hibernate reference manual there are other generators as you talked about...

increment
generates identifiers of type long, short or int that are unique only when no other process is inserting data into the same table. Do not use in a cluster.
identity
supports identity columns in DB2, MySQL, MS SQL Server, Sybase and HypersonicSQL. The returned identifier is of type long, short or int.
sequence
uses a sequence in DB2, PostgreSQL, Oracle, SAP DB, McKoi or a generator in Interbase. The returned identifier is of type long, short or int

Its a clear interpretation that increment is ruled out and also as i am using MYSQL so i need to use "identity" as the generator.

But its not clear if it will solve the problem... I need to test it first....

Can you add more to it.....

Thanks for the help.

generates identifiers of type long, short or int that are unique only when no other process is inserting data into the same table. Do not use in a cluster.

This does not work in your scenario, since every parallel servlet invocation does run in its own thread.

Identity or even betterh uuid will work fine in your scenario.

HTH
Ernst

Thanks ernst.....