class Neo {
    static hasMany = [matrix: Integer]
    static mapping = {
        matrix indexColumn: [name: "the_matrix", type: Integer]
    }
}indexColumn
Purpose
Customizes the index column definition of an indexed collection such as a List or Map
Examples
def neo = new Neo()
neo.matrix = [(1): 30, (2): 42, (3): 23]
neo.save(flush: true)Description
Usage: association_name(indexColumn:map)
Arguments:
- 
name- The name of the column as a String
- 
type(optional) - The Hibernate type.
- 
sqlType(optional) - The underlying SQL type
- 
enumType(optional) - The enum type in for type-safe Enum properties. Eitherordinalorstring.
- 
index(optional) - The index name
- 
unique(optional) - Whether it is unique
- 
length(optional) - The length of the column
- 
precision(optional) - The precision of the column
- 
scale(optional) - The scale of the column
By default when mapping an indexed collection such as a Map or List the index is stored in a column called association_name_idx which is an integer type in the case of lists and a String in the case of maps. You can alter how the index column is mapped using the indexColumn argument:
static mapping = {
    matrix indexColumn: [name: "the_matrix", type: Integer]
}