Clustering Factor
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This post is the continuation of the previous part True price of high Clustering Factor: elapsed time, SGA and CPU This time let’s try to quantify the usage of the resources applying much broader index range scan.I’ll force retrieving 10% (1 million) of rows and will pay close attention to :Elapsed times with low and…
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This post is the continuation of the previous part. Clustering Factor – tests with 10046 Let’s go through the cases represented by SELECT statements and examine the true effort measured with the number of physical reads which are hidden behind a query retrieving its data from the table, yet by the means of either one:…
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This post is the continuation of the previous part. Clustering Factor – tests with block dumps My test environment comprises a table with 10 million rows and three columns with two indexes:– ID_SORTED (unique, generated as sorted) with the index on it– ID_MESS (almost unique, generated as scattered) with the index on it– PAD (filler…
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Clustering Factor – theory Some time ago I wrote a post diving into, what I like to call the “younger siblings” of Clustering Factor (aka CLUF – this is how it’s called in the 10053 trace): AVG_DATA_BLOCKS_PER_KEY and AVG_LEAF_BLOCKS_PER_KEY—While they represent close relationship to Clustering Factor, the CLUF tends to be more recognized in the…