Sort on column def.

From: Brady, Mark <Mark.Brady_at_Constellation.Com>
Date: Wed, 9 Sep 2009 10:56:45 -0400
Message-ID: <46732D8B0755664E87B4276E3C2FF605DD9326752D_at_EXM-OMF-06.Ceg.Corp.Net>



10gR2 Docs:
SORT
The SORT keyword is valid only if you are creating this table as part of a hash cluster and only for columns that are also cluster columns. This clause instructs the database to sort the rows of the cluster on this column before applying the hash function. Doing so may improve response time during subsequent operations on the clustered data.

I don't get it. My rudimentary understanding is: Oracle uses a hash function on the clustered column that would produce a "Block offset" and place that row there... so the location of the row is predetermined, what does it buy to sort the inserts? Is it purely an efficient space allocation thing? If done in order, the less likely to chain rows? Something like that?

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Received on Wed Sep 09 2009 - 09:56:45 CDT

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