It'd be useful for clients to collect metrics of the evaluation of the pushed down predicates. Currently SargsApplier keeps track of the selected RowGroups and evaluated RowGroups:
However, we are lack of an interface in RowReader to expose the metrics. Note that sargsApplier is a private member inside RowReaderImpl. We need an interface to expose it or only its stats.
It'd also be useful if we expose other metrics of a RowReader, e.g. acutal mem usage, time elapsed in decoding/decompression, time elapsed in evaluating SearchArguments.