Improve stats reporting for group by operator

[sopel39]

Similarly as in https://github.com/trinodb/trino/commit/f46fd9c1dccb975bf480f8c7029daf7e45541b54 we could separately report hash lookups/updates and aggregations' accumulator updates to get more insight into query bottlenecks.

cc @dain @raunaqmorarka

[sug-ghosh]

I want to take this up, @sopel39 can you give more insight of this.

[sopel39]

I want to take this up, @sopel39 can you give more insight of this.

Sure go ahead. Take a look at commit https://github.com/trinodb/trino/commit/f46fd9c1dccb975bf480f8c7029daf7e45541b54. You can see that ScanFilterAndProjectOperator keeps projection and fitltering stats in PageProcessorMetrics, which are then returned as operator metrics. Similar approach could be applied for group by operator. We can measure performance of GroupByHash and Accumulator separately.

[sug-ghosh]

okay.

[piotrrzysko]

@sug-ghosh are you working on this or planning to? If not, I'd be happy to take it on.