Rows vs Columns (cont)
Storing sorted columns leads to
- potential for effective compression
- compression ⇒ more projections in same space
- no need to compress all columns (if some aren't "compressible")
- sorted data is useful in some query evaluation contexts
- e.g. terminating scan once unique match found
- e.g. sort-merge join
Only one column in each projection will be sorted
- but if even one projection has a column sorted how you need ...
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