Question

When I’m clearing a childcollection like this

table.Indizes.Clear();
session.Flush();

then NH generates a delete SQL for each item which was in the collection:

DELETE FROM x_inddef WHERE ind_name = ‘IDX_ADRKONZ_CODE’ AND tbl_name = ‘ADRESSE’
DELETE FROM x_inddef WHERE ind_name = ‘IDX_ADRKUND_EXT’ AND tbl_name = ‘ADRESSE’

…

Why isn’t it generating a statement like this?

DELETE FROM x_inddef WHERE tbl_name = 'ADRESSE'

Is something wrong with my mappings, or is this just the normal behaviour?

Simplified Code with the fluent Mapping:

public class Table
{
    public virtual string Name {get;set;
    public virtual IList<Index> Indizes { get; set; }
}

public class TableOverride : IAutoMappingOverride<Table>
{
    public void Override(AutoMapping<Table> mapping)
    {
        mapping.Table("x_tables");
        mapping.Id(x => x.Name, "tbl_name");
        mapping.HasMany(x => x.Indizes).KeyColumn("tbl_name").Inverse().Cascade.AllDeleteOrphan();
    }
}

public class Index
{
    public virtual string Name { get; set; }
    public virtual Table Table { get; set; }

    public override bool Equals(object obj)
    {
        //...
    }

    public override int GetHashCode()
    {
        //...
    }
}

public class IndexOverride : IAutoMappingOverride<Index>
{
    public void Override(AutoMapping<Index> mapping)
    {
        mapping.Table("x_inddef");
        mapping.CompositeId().
            KeyProperty(x => x.Name, "ind_name").
            KeyReference(x => x.Table, "tbl_name");
    }
}

Answer 1

You should enable batch updates option with nhibernate

First of all set adonet.batch_size property in your NHibernate configuration to value, greater then zero.

And then mark each hasMany collection with .BatchSize(xxx)

mapping.HasMany(x => x.Indizes)
   .BatchSize(25)
   .KeyColumn("tbl_name")
   .Inverse()
   .Cascade.AllDeleteOrphan();

I guess this should help