| From: | Dave Cramer <pg(at)fastcrypt(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, postgresql performance list <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: difference between a unique constraint and a unique index ??? |
| Date: | 2007-11-12 18:32:34 |
| Message-ID: | 694A5959-73AC-4C18-AA5F-489407A6CFDC@fastcrypt.com |
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| Thread: | |
| Lists: | pgsql-performance |
On 12-Nov-07, at 11:37 AM, Tom Lane wrote:
> Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
>> 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.
>
> Given the current definition of text equality, it'd be possible to
> drop
> ~=~ and have the standard = operator holding the place of equality in
> both the regular and pattern_ops opclasses. Then it'd be possible to
> support regular equality queries, as well as LIKE, with only the
> pattern_ops index.
>
That would be ideal. Having two indexes on the same column isn't
optimal.
Dave
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