Number of bitmap scans for attributes in VHCAQS
Attribute 1,000,000 tuples
(min_sf=4, z=16)
50,000 tuples
(min_sf=5, z=1)
K2 1 1
K1k 9 8
K10k 12 11
K100k 15 14
KSEQ 18 17
Indexing in Data Warehouses
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of Idea Group Inc. is prohibited.
PMap performance is better than REBSI for most of the queries in this set,
and comparable for the remaining two. For the REBSI occupying 10 times the
space of the PMap, the average performance of the PMap is better in eight of
the queries, comparable in two (HC5 and HC2) and worse in the case of two
queries, HC4 and HC1. The minimum number of pages (PMin) retrieved by
Figure 2. PMap and REBSI performance comparison: VHCAQS
1,000,000 tuples; 8K blocksize
0
00
200
00
400
00
600
00
800
00
HC 0
HC
HC
HC
HC
HC
HC
HC
HC
HC
Queries
Index Blocks
BI sf 4
BI sf 0
PAvg
8 Davis & Gupta
Copyright ?© 2007, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of
Idea Group Inc. is prohibited.
the PMap (not shown here) is less than the number of pages retrieved by any
of the REBSIs.
2. Impact.of.cardinality:.For the queries with attribute KSEQ and K100k, the
PMap performance is better for both database sizes and all scaling factors.
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