From: | Dave Cramer <pg(at)fastcrypt(dot)com> |
---|---|
To: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
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 15:13:24 |
Message-ID: | E36561B8-762D-41C9-A903-4413EE3B3253@fastcrypt.com |
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Lists: | pgsql-performance |
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
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