In message
<[EMAIL PROTECTED]>, Adrian
Merrall <[EMAIL PROTECTED]> writes
And on, and on, until the particular bit of data is found.
So... (this being one of the overwhelmingly elegant things about the
Pickuverse) this means that in a properly sized hashed file NO MATTER
HOW BIG it only takes one disk read to get to any record given a known
key. Ask your local Oracle/Sybase/Informix/SQL Server DBA if they can do
that. Stand back though, they tend to sputter alot.
But won't this only work if your data fits into the modulo that
matches your page size? If your data is lumpy and doesn't nicely fit
into the page size/file modulo selected you get level 1overflow and
more disk IO.
The stats I've come across (yes, they're old, they came from Prime) say
that PROVIDED Adrian's "properly sized" caveat is followed, even when
you have level 1 overflow and lumpy data, your 1 merely increases to an
average of 1.05. In other words, 19 out of 20 attempts still hit first
time...
Cheers,
Wol
--
Anthony W. Youngman <[EMAIL PROTECTED]>
'Yings, yow graley yin! Suz ae rikt dheu,' said the blue man, taking the
thimble. 'What *is* he?' said Magrat. 'They're gnomes,' said Nanny. The man
lowered the thimble. 'Pictsies!' Carpe Jugulum, Terry Pratchett 1998
Visit the MaVerick web-site - <http://www.maverick-dbms.org> Open Source Pick
-------
u2-users mailing list
[email protected]
To unsubscribe please visit http://listserver.u2ug.org/
