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Need clarity on Page Compression


Need clarity on Page Compression

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Jayakumar Krishnan
Jayakumar Krishnan
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Hi Gurus,

Few queries on the Prefix compression logic. As per PrefixComp2 pic, "In the first column of the first row, the value 4b indicates that the first four characters of the prefix (aaab) are present for that row, and also the character b. This makes the resultant value aaabb, which is the original value." This I could understand based on PrefixComp1 and PrefixComp2 images.

But in Dictionary compression, 4b is being referred by Col1 and Col2 values, but as per image 1 the col1 & 2 values are aaabb (4b=first 4 ltrs(ie aaab) + b) & aaaab (4b=first 4 ltrs(ie aaaa) + b) so the first 4 ltrs are different in the columns but how it can refer 4b (CI) for col1 and Col2 ?

I'm not sure I misunderstood or ??? Hehe ... Kindly clarify.

Have a good day...

Warmest
Jay.

Thanks
Jay
http://www.sqldbops.com
Attachments
PrefixComp1.gif (15 views, 2.00 KB)
PrefixComp2.gif (14 views, 6.00 KB)
PrefixComp3.gif (12 views, 4.00 KB)
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