Re: difference between a unique constraint and a unique index ???

[Dave Cramer <pg(at)fastcrypt(dot)com>]

On 12-Nov-07, at 9:56 AM, Alvaro Herrera wrote:

> Dave Cramer wrote:
> > In order to get like queries to use an index with database  
> > initialized with
> > a UTF-8 character set I added a unique index to a table with a
> > varchar_pattern_ops
> >
> > This table already had a unique constraint on the column so I  
> > dropped the
> > unique constraint.
> >
> > I can't give exact measurements however this caused my application  
> > to slow
> > down considerably.
> >
> > The only thing I can figure is that the varchar_pattern_ops  
> > operator is
> > significantly slower ???
> >
> > Is there some other piece of the puzzle to fill in ?
>
> Well, AFAIK the index with varchar_pattern_ops is used for LIKE  
> queries,
> whereas the other one is going to be used for = queries.  So you  
> need to
> keep both indexes.
You would be correct, thanks for the quick answer.

Dave