Hello,
We're doing some performance testing of the essential column family feature, and we're seeing some performance degradation when comparing with and without the feature enabled:

                          Performance of scan relative
% of rows selected        to not enabling the feature
---------------------    --------------------------------
100%                            1.0x
 80%                            2.0x
 60%                            2.3x
 40%                            2.2x
 20%                            1.5x
 10%                            1.0x
  5%                            0.67x
  0%                            0.30%

In our scenario, we have two column families. The key value from the essential column family is used in the filter, while the key value from the other, non essential column family is returned by the scan. Each row contains values for both key values, with the values being relatively narrow (less than 50 bytes). In this scenario, the only time we're seeing a performance gain is when less than 10% of the rows are selected.

Is this a reasonable test? Has anyone else measured this?

Thanks,

James





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