Grails save() Domain Object actually does a Select?

I am trying to take a JSONObject I posted to my groovy controller. I can pass the object, see the JSON data and then create a Domain Object out of it. When I save it to write to the database开发者_Python百科 it does a Select instead.

def save = {
    def input = request.JSON
    def instance = new Customers(input)
    instance.save()
}   

here is my debug sql output

Hibernate: 
select
    this_.customers_id as customers1_237_0_,
    this_.customers_default_address_id as customers2_237_0_,
    this_.customers_dob as customers3_237_0_,
    this_.customers_email_address as customers4_237_0_,
    this_.customers_email_address2 as customers5_237_0_,
    this_.customers_fax as customers6_237_0_,
    this_.customers_firstname as customers7_237_0_,
    this_.customers_gender as customers8_237_0_,
    this_.customers_lastname as customers9_237_0_,
    this_.customers_membertype as customers10_237_0_,
    this_.customers_memo1 as customers11_237_0_,
    this_.customers_mname as customers12_237_0_,
    this_.customers_newsletter as customers13_237_0_,
    this_.customers_password as customers14_237_0_,
    this_.customers_point_date as customers15_237_0_,
    this_.customers_telephone as customers16_237_0_,
    this_.customers_total_points as customers17_237_0_,
    this_.customers_username as customers18_237_0_ 
from
    customers this_ 
where
    this_.customers_username=?

Don't know what would be causing this.

Looks like you have a unique constraint on username. Grails does a select to check uniqueness since assumed that reading one row is a lightweight action and it's preferable to triggering a unique constraint violation and exception.

An alternative is to remove the unique constraint in the domain class and add the unique constraint manually in the database.

Did you tried something like :

Customers cust = new Customers(input);
println ("cust = "+cust);
cust.save();