From: | Rob Wultsch <wultsch(at)gmail(dot)com> |
---|---|
To: | "David E(dot) Wheeler" <david(at)justatheory(dot)com> |
Cc: | Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Covering Indexes |
Date: | 2012-06-28 13:02:23 |
Message-ID: | CAGdn2ugWfeuJO-QVzsYc=NOWDdh0WpTunOWLOZ-0+9QZjh15=w@mail.gmail.com |
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Lists: | pgsql-hackers |
On Thu, Jun 28, 2012 at 8:16 AM, David E. Wheeler <david(at)justatheory(dot)com> wrote:
> Hackers,
>
> Very interesting design document for SQLite 4:
>
> http://www.sqlite.org/src4/doc/trunk/www/design.wiki
>
> I'm particularly intrigued by "covering indexes". For example:
>
> CREATE INDEX cover1 ON table1(a,b) COVERING(c,d);
>
> This allows the following query to do an index-only scan:
>
> SELECT c, d FROM table1 WHERE a=? AND b=?;
>
> Now that we have index-only scans in 9.2, I'm wondering if it would make sense to add covering index support, too, where additional, unindexed columns are stored alongside indexed columns.
>
> And I wonder if it would work well with expressions, too?
>
> David
IRC MS SQL also allow unindexed columns in the index.
--
Rob Wultsch
wultsch(at)gmail(dot)com
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