Re: difference between a unique constraint and a unique index ??? - Mailing list pgsql-performance

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.

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