Ann,
thank you for your detailed explanation.

> Many of us had introductory data structure courses

:-) oh yes, I remember something from time, when I has study on
university (10 years ago)

> design where the index developed was variable depth ... some

branches

> got really long, others were very short.

There aro also always balanced-trees like AVL tree, but this type of
trees is apparently unusable for databases ?

> 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 ?
Are these trees 2-3 B-trees, or each parent can have more than 3
childs ?
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 ?
As I understand, if only leaf nodes contains pointers to data rows,
then this tree will be keept good balanced, without requirements
of "rebalancing" ?

-Laco.