Thanks Ann,
-Laco.

--- In firebird-support@yahoogroups.com, "Ann W. Harrison"
<aharrison@...> wrote:

>
> lacakus wrote:
> >
> >> In Firebird, an index is made up of pages - the same size as all
> > pages
> >> in the database. It starts as a single page. Index entries

(called

> >> nodes) are added to the page in order by key. When the page

fills,

> >> two other index pages are added.
> >>
> > I guess, that Fb uses B-trees, true ?
>
> There are lots of varieties of B-Trees, but yes, it's a B-Tree
> variant.
>
> > Are these trees 2-3 B-trees, or each parent can have more than 3
> > childs ?
>
> Each parent is a page and contains as many nodes as fit on a page.
> Nodes in the upper (parent) levels contain the key, a record
> number of a record that contains that key value and the page number
> of the lower level page that starts with that key and record number.
> So, the number of "children" a "parent" page can have depends on
> the page size and the size of the compressed keys.
>
>
> > Contains intermediate nodes, also pointers to data rows (or only
> > pointers to deeper level index nodes?, or only leaf nodes

contains

> > pointers to data rows ?
>
> Upper level pages contain only pointers to lower level pages and
> actual record pointers are only on the lowest level pages.
>
> > As I understand, if only leaf nodes contains pointers to data

rows,

> > then this tree will be keept good balanced, without requirements
> > of "rebalancing" ?
>
> That's part of it, though garbage collection is also a factor.
>
>
> Regards,
>
>
> Ann
>