From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
---|---|
To: | Dave Cramer <pg(at)fastcrypt(dot)com> |
Cc: | postgresql performance list <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: difference between a unique constraint and a unique index ??? |
Date: | 2007-11-12 14:56:30 |
Message-ID: | 20071112145630.GC14247@alvh.no-ip.org |
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Thread: | |
Lists: | 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.
--
Alvaro Herrera http://www.amazon.com/gp/registry/5ZYLFMCVHXC
Officer Krupke, what are we to do?
Gee, officer Krupke, Krup you! (West Side Story, "Gee, Officer Krupke")
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