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

[Thomas S. <ts...@ib...>]

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

Makes sense. How does the engine know when to garbage collect an index 
entry?


Thanks,
Thomas