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Re: difference between a unique constraint and a unique index ???
- 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: Mon, 12 Nov 2007 13:32:34 -0500
On 12-Nov-07, at 11:37 AM, Tom Lane wrote:
That would be ideal. Having two indexes on the same column isn't optimal.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 tokeep 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.
Dave
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- difference between a unique constraint and a unique index ???
- From: Dave Cramer
- Re: difference between a unique constraint and a unique index ???
- From: Alvaro Herrera
- Re: difference between a unique constraint and a unique index ???
- From: Tom Lane
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