secondary_statistics.h

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#pragma once
 
class THD;
class Field;
 
namespace secondary_statistics {
 
/**
 If secondary engine is available, return number of distinct values (NDV)
 information for specified field.
 
 @param thd The current thread.
 @param field The field we request NDV for
 
 @returns NDV if secondary engine is active and has information on column,
          -1.0, otherwise
 */
double NumDistinctValues(THD *thd, const Field &field);
 
}  // namespace secondary_statistics