On Tue, Jul 17, 2012 at 6:08 PM, Simon Riggs <si...@2ndquadrant.com> wrote:
> On 17 July 2012 16:54, David E. Wheeler <da...@justatheory.com> wrote: > > Yeah, but that index is unnecessarily big if one will never use c or d > in the search. The nice thing about covering indexes as described for > SQLite 4 and implemented in MSSQL is that you can specify additional > columns that just come along for the ride, but are not part of the indexed > data: > > > > CREATE INDEX cover1 ON table1(a,b) COVERING(c,d); > > > > Yes, you can do that by also indexing c and d as of 9.2, but it might be > nice to be able to include them in the index as additional row data without > actually indexing them. > > Can you explain what you mean by "without actually indexing them"? > ISTM that it is a non-feature if the index is already non-unique, and > the difference is simply down to the amount of snake oil applied to > the descriptive text on the release notes. > It would be useful in non-unique indexes to store data without ordering operators (like xml).