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Home -> Community -> Usenet -> c.d.o.server -> Re: nonunique index on unique values
On Aug 28, 3:22 pm, ciapecki <ciape..._at_gmail.com> wrote:
> hi,
>
> is there a big lost in performance if there is a nonunique index on
> the column that holds only unique values (like primary key)?
>
> thanks
> chris
If you mean a nonunique index, compared to a unique index, is used to
enforce a unique constraint, there's performance penalty in terms of
generated redo when you get error ORA-1 (unique constraint violated).
See
http://orafaq.com/papers/oracle_redo_generation_wp.pdf
Yong Huang Received on Wed Aug 29 2007 - 10:34:33 CDT
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