RE: Unique Index Re-design

> create unique index mho_ind on t4 (case when a = 90996518 then null
else a end, case when b is not null then b end);

Strictly speaking, "case when b is not null then b end" will have same values as just simple "b"
And you will need to rewrite predicates(or maybe create view like "create view t4 select case when a = 90996518 then null else a end as A, ... from old_t4" )

> When I asked the client what is the particularity of this a value
(90996518) he answered that this a dummy value used for testing (yes for testing
> in PRODUCTION).

Am i right that all rows with such value are just dummy rows? In that case, i think, we could consider table partitioning with separation dummy rows from others and local indexing.

--
Best regards,
Sayan Malakshinov
http://orasql.org
--
http://www.freelists.org/webpage/oracle-l