Re: Functions and Relations
Date: 21 Nov 2006 22:53:32 -0800
> Aloha Kakuikanu wrote:
> > vc wrote:
> > > In a sort of way, yes, it does if you think that a 5 times difference
> > > in the execution time is OK.
> > Since, the difference the other way is routinely orders of magnitude, 5
> > times time difference is nothing.
> That is odd. I've never seen "the difference the other way" being
> "orders of magnitude". There's always the first time as they say.
> Please provide a test case of a HJ being at least 10 times slower than
> a NL join for the same collection of data of course.
Table A - 1 row
Table B - 1G rows
join key is a unique index on B
NL join executioon scans table A.- 1 block read,
then navigates 3-4 levels in the index which amounts to 3-4 block
then access a row in table B - 1 more block read.
HJ had to scan full table B.
> But it's rather boring a subject for the theory group would
> not you agree ?
Ceased and desisted. Received on Wed Nov 22 2006 - 07:53:32 CET