Mayank Maheshwari wrote:
Hi,
I was trying out selection queries with varying selectivity factors on a 1 million tuple relation. The selectivity factors for predicates were 0.1%, 1% and 10% of the entries in the column and the data type of the column is int. What I'm seeing is that the execution time increases with selectivity factors going from 0.1% to 1% to 10%. I'm not sure why this is happening though, considering its a column-store well, intermediate results are created, which explains the time increase.
system. Should this be attributed to increase in CPU time or disk I/Os or any other factor? What my understanding of column-store systems is that the execution time should remain constant for varying selectivity factors for the same column. Any help would be appreciated. no, it remains constant only if there is no result table produced. Be aware that MonetDB always materializes the intermediat results.
Thanks
Mayank
Mayank Maheshwari mayank@cs.wisc.edu
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