> > ... that being said (and I took a quick test with 10000
> > randomly-inserted
> > records and fetched them in index order) if the data's in the
> > cache, the
> > speed difference is insignificant.
>
> As long as everything fits into the system cache and is
> already in there, this test is moot.
Oh, if we want to test how cache is affected by index-nature of
MySQL-BDB then 10000 rows table is toooo small. It adds just
2 levels of internal pages (including root) and ~25 8k pages
to ~ 190 pages of true heap table: additional pages will be
cached very fast, just while fetching first 25 rows from table -:)
Now create 10000000 rows table (~ 25000 additional pages, 3 internal
levels) and fetch random 10000 rows...
...And again - does MySQL-BDB really read *table* for query like
select a from foo order by a? I remember that MySQL is smart to
read only index when possible...
Vadim
