Method: Adds zeroes for segments not present in the data selection.

Method: Adds missing segments to intervals, modifies $data.

Method: Filters definitions for SELECT clauses based on query_args and joins them into one string usable in SELECT clause.

Method: Update row-level db result for segments in ‘totals’ section to the format used for output.

Method: Merges segmented results for totals response part.

Method: Merges segmented results for intervals response part.

Method: Constructor.