Aggregates

The filter unit also computes various summaries or aggregates of the data, which are returned in fields in the job structure. The meaning of these values varies slightly depending on whether the output is nominally a bit vector or an array:

Field	Bit Vector Meaning	Array Meaning
qpl_job.first_index_min_value	Index of first 1-bit in output	Min value over output
qpl_job.last_index_max_value	Index of last 1-bit in output	Max value over output
qpl_job.sum_value	Number of 1-bits in output	Sum of output values

Considering a bit vector output, e.g., doing a scan operation, these values can tell the software how sparse the result is, as well as where one should start and end walking through the results to find all the 1’s.

Note

The meaning of the aggregates is not changed by the output modification (see Output Modification). If the output is nominally a bit vector, and due to the output modification, the output actually contains 32-bit indices, the aggregates still reflect the bit vector values.