On 28 June 2012 13:16, David E. Wheeler <david@justatheory.com> wrote:
> 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.
Just to be clear, the ability to have covered indexes is already in
9.2, I updated the release notes to explain that a few months back.
-- Simon Riggs http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services