PromQL: topk/bottomk over bare instant vector produces unexpected Aggregate(Sum)

[milindsrivastava1997]

Summary

topk and bottomk applied to a bare instant vector (no range function) lower to Limit { Sort { Aggregate(Sum) { Scan } } }. The Aggregate(Sum) is unexpected — a bare instant vector is not a sum aggregation.

Reproduction

# P2 — topk over instant vector
topk(5, http_requests_total)

# P6 — bottomk over instant vector
bottomk(5, http_requests_total)

L3 output for P2:

Limit {
    n: 5,
    child: Sort {
        keys: [SortKey { ascending: false }],
        child: Aggregate {
            aggs: [Sum { col: None }],
            child: Scan { source: TimeSeries { metric: "http_requests_total" } }
        }
    }
}

Expected

A bare instant vector should not introduce a Sum aggregate. Expected output is Limit { Sort { Scan } } or similar without the wrapping aggregation.

Reproduce via example

cargo run -p asap-control-lower --example topk_ir

Labels: P2, P6

[zzylol]

Verified fixed on latest main (via PR #31, which removed the implicit cross-series Sum for bare-selector topk).

Reproduced with cargo run -p asap-control-lower --example topk_ir:

• topk(5, http_requests_total) (P2) → Limit { Sort { keys:[col1 desc] } → Scan } — no Aggregate(Sum)
• bottomk(5, http_requests_total) (P6) → Limit { Sort { ascending:true } → Scan } — no Aggregate(Sum)

Matches the issue's Expected output. Closing.