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Message Posted: Wed, 26 Jan 2011 @ 16:22:57 GMT
Hi all. I have a simple question around value compression: is it better to compress all known values or only the most frequent values?
Simple example: Currency Code in a transactional table has about 50+ distinct values, but only 9 occur > 1%. All possible values for the column are known, and fewer than 255 exist, but most values occur less than 1% of the time.
Col_Val Val_Pct ------- ------- USD 59.1% EUR 7.6% CNY 6.3% JPY 5.0% BRL 3.7% GBP 3.3% CAD 2.9% AUD 2.6% INR 2.5%
I can add the other 40 values to the value list. But would that create greater operational efficiency or less? I suppose the simple answer is: a little less efficient load and a little more efficient retrieval. In general we want to optimize for retrieval. Therefore do you advise that we add all possible values? Or only the most frequent values?
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