QueryStats
What a query found and what it cost.
The counters are the point rather than decoration. "The index answered without opening a document" is a claim about work, and a result set cannot demonstrate it — which is why every assertion the test suite makes on these numbers sits in the same test as the differential equality against a full scan. On its own documentsRead == 0 passes trivially for a query that returned nothing.
Read them off a cursor at any point; they are final once it is exhausted.
Properties
Keys the plan offered, before the recheck and before deduplication across sources.
Documents whose bytes were examined: scanned, rechecked, or opened for a projection.
Rows whose projected fields were read out of shredded columns rather than out of a document.
Whether the plan had to merge memtables, which no sidecar can ever cover.
Segments answered from sidecars.
Segments the plan had to read, because no index covered them at this snapshot.
Segments whose column bounds or physical type ruled the predicate out without a block read.