public class Article
{
    public Article() {}
    public Article(String name) {this.name = name; }

    public String getName() { return this.name; }

    private String name;
}

public class Invoice
{
    public Invoice() {}
    public Invoice(String num, Date created) {this.num = num; this.created=created;}

    public String getNum() { return this.num;}
    public String getCreated() { return this.num;}

    private String num;
    ptivate Date created;
    private Article[] lines;
}

create table Article
(
article_id integer primary key,
name varchar2( 50 )
);
create index ix_Article_Name on Article(Name);

create table Doc
(
doc_id integer primary key,
num varchar2( 50 ),
created date
);

create table DocLine
(
doc_id integer references Doc,
article_id integer references Article,
unique(Doc, Article)
);
create index ix_DocLine_Article on DocLine(Article);
select distinct doc.num, doc.created from Doc, DocLine, Article
where doc.doc_id = DocLine.doc_id 
and DocLine.article_id = Article.article_id 
and Article.name like '%помидор%';

query.constrain(Invoice.class);
query.descend("lines").descend("name").constrain("помидор").like();

Db4o.configure().objectClass(Invoice.class).objectField("lines").indexed(true);

Db4o.configure().objectClass(Invoice.class).objectField("lines").indexed(true);

Db4o.configure().objectClass(Invoice.class).objectField("lines").indexed(true);