Re: [Firebird-devel] "Covering" index?

[Ann H. <an...@qb...>]

On Sun, Jan 27, 2013 at 3:23 PM, Dimitry Sibiryakov <sd...@ib...>wrote:

> 27.01.2013 21:17, Thomas Steinmaurer wrote:
> > Is Firebird able here to serve the result here out of the index or does
> > it need to lookup data by following the index key to the row data?
>
>    There is no data in index. And no information about transaction created
> an index entry.
> So, yes, Firebird has to look at real data.
>
>
Just to amplify Dimitry's answer, without transaction information, there's
no way to tell whether an index entry points to a record version that's
appropriate to your transaction.  So even if you find an index entry that
exactly matches the data you want, you still have to read the record.

Cheers,

Ann