Re: Covering Indexes

On Thu, Jun 28, 2012 at 8:16 AM, David E. Wheeler <david@justatheory.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,
whereadditional, 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@gmail.com