Histogram-Aware Sorting for Enhanced Word-Aligned Compression in Bitmap Indexes
Abstract
Bitmap indexes must be compressed to reduce input/output costs and minimize CPU usage. To accelerate logical operations (AND, OR, XOR) over bitmaps, we use techniques based on run-length encoding (RLE), such as Word-Aligned Hybrid (WAH) compression. These techniques are sensitive to the order of the rows: a simple lexicographical sort can divide the index size by 9 and make indexes several times faster. We investigate reordering heuristics based on computed attribute-value histograms. Simply permuting the columns of the table based on these histograms can increase the sorting efficiency by 40%.
- Publication:
-
arXiv e-prints
- Pub Date:
- August 2008
- DOI:
- 10.48550/arXiv.0808.2083
- arXiv:
- arXiv:0808.2083
- Bibcode:
- 2008arXiv0808.2083K
- Keywords:
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- Computer Science - Databases;
- H.3.2;
- E.1
- E-Print:
- To appear in proceedings of DOLAP 2008