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i/o estimation

Author

Topic

KazaX
Starting Member

28 Posts

Posted - 2008-11-25 : 06:48:03

How can one estimate required i/o in blocks for block nested loop join and naive join?

if I have 10^6 records in table R that occupies 100mb
and 10^5 rec. in table S that occupies 200mb.
the blocks read from disk are 50kb.Cache holds six blocks, a 1-block input buffer for one table, a 4-block buffer for the
other, and a 1-block output buffer.

And perform below query.

SELECT R.A, S.C
FROM R, S
WHERE R.B = S.B

is there a formula ? or sth?

Really thanks

SwePeso
Patron Saint of Lost Yaks

30421 Posts

Posted - 2008-11-25 : 06:51:04

It depends on a few things, such as present indexes, fragmentation and so on..

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