How to make GORM create an index on Map? - grails

Question

In my Grails 2.3.7 project, I have a Product domain class, like this:
class Product {
String code
String description
Map attributes
static constraints = {
code(unique: true)
}
static mapping = {
code index: 'Code_Idx'
attributes fetch: 'join'
cache true
id generator: 'hilo'
}
}
It translates into this database:
create table product (id bigint not null, version bigint not null, code varchar(255) not null unique, description varchar(255) not null, primary key (id));
create table product_attributes (attributes bigint, attributes_idx varchar(255), attributes_elt varchar(255) not null);
create index Code_Idx on product (code);
With some 4000 products in database, the scaffold listing shows them just fine.
Except, when I click "sort" on code - because there is no index - so my server does this:
explain select this_.id as id14_0_, this_.version as version14_0_, this_.code as code14_0_, this_.description as descript4_14_0_,
attributes2_.attributes as attributes14_2_, attributes2_.attributes_elt as attributes3_2_, attributes2_.attributes_idx as attributes2_2_
from product this_ left outer join product_attributes attributes2_
on this_.id=attributes2_.attributes
order by lower(this_.code) desc limit 90, 100
+----+-------------+--------------+------+---------------+------+---------+------+-------+---------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+--------------+------+---------------+------+---------+------+-------+---------------------------------+
| 1 | SIMPLE | this_ | ALL | NULL | NULL | NULL | NULL | 4086 | Using temporary; Using filesort |
| 1 | SIMPLE | attributes2_ | ALL | NULL | NULL | NULL | NULL | 43975 | |
+----+-------------+--------------+------+---------------+------+---------+------+-------+---------------------------------+
Obviously, this takes ages. I can manually add the index:
ALTER TABLE `product_attributes` ADD INDEX(`attributes`);
and then it works OK. I think it should have been created automatically in the first place - there is very little sense in this schema without the index - but OK, I can ping Gorm to do it. My question is - what can I put into the domain class to have Gorm add this index ?

Answer 1

Grails doesn't automatically create indexes on such columns as 'attributes' in your example. In order to create and manage these indexes I highly recommend using the Database Migration Plugin. The documentation is well written, and outlines how to use it.