Qingqing Zhou wrote:
Oracle 9 uses the grammar like this:
CREATE INDEX ... [ COMPRESS <number_of_first_columns> ]
So it gives the flexibility of choosing optimal number of coulumns to the
user. The script mentioned in the article guesses the optimal number by
estimating the size of each choice. But I am thinking we can do it better:
(1) we don't require that the compressed number of columns on each page are
the same; (2) when we build up index bottom-up, we can determine this number
for each page automatically by maximizing the number of items within a page.
Are there any gains in eliminating duplicate values in result-sets? I'd
guess that many/most large result-sets are sorted which should make it
possible to get away with a "same as last row" marker when the whole set
is returned to a client.
Of course, this is where someone turns around and tells me we do this
already :-)
--
Richard Huxton
Archonet Ltd
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TIP 6: explain analyze is your friend