Matteo,

From: "Nando Dessena" <nandod@...>

> index in two or three (non unique) slices, and then enforce uniqueness
> by means of a trigger or two.
> This has some disadvantages, too.

In fact, the disadvantage is that the uniqueness can not be enforced with
triggers ! IB has a stupid low (about 200-300 bytes - I don't know for sure
but is documented) limit for an index size. So, if you want uniqueness you
should use smaller fields in the unique key. This could be done by
indirection of large fields like this:

create table FILES (
id integer not null,
file varchar(200) not null,
constraint FILES_PK primary key (id, file)
);

Same way:

create table PERCORSOS (
...

Note that a primary key is allways an unique one, and the theory said that
each table should have one.
After this you can make a reference in your table to a file by it's ID, like
this:

CREATE TABLE TEST (
Protocollo SMALLINT NOT NULL,
Host SMALLINT NOT NULL,
Porta SMALLINT NOT NULL,
Percorso_id integer NOT NULL,
File_id integer NOT NULL,
Status SMALLINT DEFAULT '0',
CONSTRAINT test_pk PRIMARY KEY (Host, Percorso_id, File_id),
CONSTRAINT test_file_fk FOREIGN KEY (File_id) REFERENCES files (ID),
CONSTRAINT test_percorsos_fk FOREIGN KEY (Percorso_id) REFERENCES
percorsos (ID)
);

Note that I don't know what "percorso" means and it may sound strange or
stupid.
Anyway, this is just a posibility, your imagination may find others. The
ideea is not having very large keys (it is good for performance, too).

Raul.



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