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PromQL: topk with 'by' clause over bare instant vector fails with column resolution error #22
Description
Summary
topk by (label) (k, metric) applied to a bare instant vector fails at L2→L3 conversion with a column resolution error. Related to the Aggregate(Sum) wrapping bug in bare instant vectors.
Reproduction
# P8 — topk with by, instant vector
topk by (service) (5, http_requests_total)
Error:
ERR: L2→L3 conversion failed: column resolution failed:
ColumnRef::SampleValue has no `value` column in schema (have: ["service", "sum"])
Context
topk(5, http_requests_total) (without by) produces Aggregate(Sum) instead of a plain scan. When by is added the sum aggregate's output schema no longer contains a value column, breaking SampleValue resolution.
Reproduce via example
cargo run -p asap-control-lower --example topk_ir
Labels: P8
Activity
zzylol commentedon Jul 2, 2026
Verified fixed on latest
main(via PR #31).topk by (service) (5, http_requests_total)(P8) now lowers cleanly — no column-resolution error:The
servicelabel is preserved and routed toSort.partition_by(no implicitSumcollapsing it). Reproduced viacargo run -p asap-control-lower --example topk_ir. Closing.