Schema Export Errors while launching grails application

Question

I am trying to follow the Grails application from the book Grails 2 - A Quick start guide. The grails version that i am using is 2.4.4 on Ubuntu 14.04 with the open jdk 7

I am getting the following error

 Error 2015-03-09 20:05:02,117 [localhost-startStop-1] ERROR hbm2ddl.SchemaExport  - HHH000389: Unsuccessful: alter table tek_event drop constraint FK_1xbf5b7edlnmgmrc90jhbyvg7 if exists
| Error 2015-03-09 20:05:02,118 [localhost-startStop-1] ERROR hbm2ddl.SchemaExport  - Table "TEK_EVENT" not found; SQL statement:

There is nothing in my application except two domain classes and scaffolded controllers ...

Here are the domain classes TekUser and TekEvent

class TekEvent {

    String city
    String name
    TekUser organizingUser
    String venue
    Date startDate
    Date endDate
    String description

    String toString(){
        "$name, $city"
    }

    static constraints = {      
        name()
        city()
        description maxSize:5000
        organizingUser()
        venue()
        startDate ()
        endDate()               
    }
}

And the TekUser Domain class

    class TekUser {


    String fullName
    String userName
    String password
    String email
    String website
    String bio

    String toString(){
        fullName
    }

    static constraints = {    
        fullName()
        userName()
        email()
        website()
        bio maxSize:5000
    }
}

The controllers for them are pretty barebones

class TekEventController {
    def scaffold = TekEvent;
}

class TekUserController {
    def scaffold = TekUser;
}

I am not able to follow what is going wrong here ...or is it a benign error that I could just ignore.

Also this started happening when I changed the datatype of organizingUser in the TekEvent class from String to TekUser

Answer 1

These are ignorable errors - there's nothing bad happening. Unfortunately the Hibernate developers changed the logging strategy in Hibernate 4, and that's what you're seeing.

In Hibernate 3, using "create-drop" means to drop all current mapped tables and associated objects (sequences, joins, etc.), then run the create statements, and if the jvm shuts down cleanly, drop all of the tables again at the end. "create" is slightly different in that it does all of the drops and all of the creates, but doesn't do anything at shutdown. This is one I use often since it lets me view data in disk-based databases after the app shuts down.

So the core issue is that the initial drop statements are missing the "if exists" clause, and sometimes not everything that Hibernate is trying to drop exists. So you get these scary looking errors, but they're harmless since they're just telling you that some of the things that were supposed to be deleted were never created.

In Hibernate 3, these errors were stored in a list of strings that you could access after running the script. In Hibernate 4 they changed it to log the errors, I assume since not all errors in that phase are ignorable, so it's better to have false positives in with the real issues than everything hidden in a list that is probably rarely checked.

You can choose to ignore these (at the risk of also ignoring unrelated real error messages), or use a custom Dialect that generates the proper SQL. One example is here