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Archives of the TeradataForum
Message Posted: Mon, 22 Oct 2007 @ 17:32:42 GMT
| Subj: | | Re: Compression Algorithm |
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| From: | | Dieter Noeth |
Barner Eric wrote:
| | Can you expand on your below comment. | |
| | "Now there are 64-bit systems, so this is even worse, due to pad byte fields and alignment issues :-(" | |
It's more complicated to calculate if an additional presence byte will result in an actual row size increase. And if converting a Varchar to a
compressed Char will result in a different size for the Varchar Offset Array.
Check the Database Design manual
Chapter 15: Database-Level Capacity Planning Considerations
Base Table Row Format
| | This is a harrowing thought when thinking about converting from our 32 bit MP-RAS to 64bit Linux. | |
| | I have not put that much thought to the idea, but from what I can understand from your statement, this could have a significant performance
impact in migrating to a new OS. | |
At least perm space usage will be increased. Quote: "but studies with more realistic customer data in the field indicate that the identical row
on a 64-bit system is likely, on the average, to see a size increase closer to 7 percent over its size on a 32-bit system"
| | I guess my question is, in your opinion, will the switch to 64 bit > > significantly degrade the effectiveness of MultiValue
Compression? | |
Probably not, it's just much harder to pre-calculate the actual benefit.
Dieter
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