Expose more metrics when explain analyzing the region scan plan

[evenyag]

What type of enhancement is this?

User experience, Performance

What does the enhancement do?

Currently, the region scan plan only exposes a limited number of metrics in EXPLAIN ANALYZE. It'd be helpful if we could expose more metrics from mito.

There are several tasks:

• Expose existing scanner metrics to the execution plan
• Collect more scanner metrics
  • Reader metrics for each SST
  • Reader metrics for each index file
  • Cache metrics
• Support explain analyze verbose Push down analyze verbose to region #4408

Implementation challenges

Collecting cache metrics during scan may require putting the metrics context in different readers and caches.