| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Get more from indices. |
| Date: | 2013-10-31 15:05:36 |
| Message-ID: | CA+TgmoYT8uY9YFk1bNVJuSjxH8N+M+unfKVSS4MfzD3w=LbEkQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Oct 31, 2013 at 10:59 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> However, if the index is unique, wouldn't
> scanning the index produce data that actually satisfies the longer sort
> key? It doesn't matter what the values of c,d are if there are no
> duplicates in the a,b columns. So maybe as a separate patch, we could
> look at claiming that a unique index satisfies the entire query_pathkeys
> if it matches the first N columns of that.
That would be really spiffy.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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