Grails alters my table using not null instead of null - grails

Question

I'm developing a personal project with grails in order to learn this powerful tool.
I have encountered this problem when adding two new fields (x,y) to my domain class "Post":
class Post {
long id;
Date creationDate;
String text;
byte[] image;
Style style;
long likeCount;
long dislikeCount;
User owner;
//coordinates on the wall
int x;
int y;
//this is probably to remove
static hasMany = [judgment : Judgment];
static constraints = {
text(nullable:true, maxSize:5000);
image(nullable:true, maxSize:1000000);
creationDate(nullable:true);
x(nullable:true);
y(nullable:true);
}
}
I added x and y after I create some data (Post records) on my postgres database.
But when I run-app in grails console this error comes up:
| Error 2012-03-04 12:04:23,670 [pool-5-thread-1] ERROR hbm2ddl.SchemaUpdate - Unsuccessful: alter table post add column x int4 not null
| Error 2012-03-04 12:04:23,672 [pool-5-thread-1] ERROR hbm2ddl.SchemaUpdate - ERROR: column "x" contains null values
this is very strange because i declared in constraint x,y to be nullable.. so why grails try to alter my table declaring x and y to be not null?

Answer 1

They're primitive int fields, so nullable doesn't make sense. You can't store a null value in the class instance, and if you have a null value in the database there's no sensible default conversion to an int value. You may consider 0 a sensible value for null, but 0 and null aren't equivalent in general.
If you want to allow null values for primitive numbers (int, long, etc.) or for boolean use the non-primitive Object classes Integer, Long, Boolean, etc. Another problem with primitive types is validation. Since they default to 0 (or false for boolean) you can't know whether the user chose 0 or false or if they didn't make a choice at all and you just have the default values from the constructor. So making them non-primitive leaves them null and you can know whether they made a choice or not.
Also, unrelated - you don't need to declare the id field, since Grails adds one for you anyway. And lose the semicolons ;)