What causes "invalid reduce to operator: %s" in SigNoz/signoz?

invalid reduce to operator: %s

Error message

invalid reduce to operator: %s

What it means

ReduceToOperator.Validate() rejects a reduce-to operator that is not one of the four supported values: last, sum, avg, min, max. The reduce-to operator controls how a time series is collapsed to a single value in builder queries (typically for table/value panels).

Source

Thrown at pkg/query-service/model/v3/v3.go:181

	}
}

type ReduceToOperator string

const (
	ReduceToOperatorLast ReduceToOperator = "last"
	ReduceToOperatorSum  ReduceToOperator = "sum"
	ReduceToOperatorAvg  ReduceToOperator = "avg"
	ReduceToOperatorMin  ReduceToOperator = "min"
	ReduceToOperatorMax  ReduceToOperator = "max"
)

func (r ReduceToOperator) Validate() error {
	switch r {
	case ReduceToOperatorLast, ReduceToOperatorSum, ReduceToOperatorAvg, ReduceToOperatorMin, ReduceToOperatorMax:
		return nil
	default:
		return fmt.Errorf("invalid reduce to operator: %s", r)
	}
}

type QueryType string

const (
	QueryTypeUnknown       QueryType = "unknown"
	QueryTypeBuilder       QueryType = "builder"
	QueryTypeClickHouseSQL QueryType = "clickhouse_sql"
	QueryTypePromQL        QueryType = "promql"
)

func (q QueryType) Validate() error {
	switch q {
	case QueryTypeBuilder, QueryTypeClickHouseSQL, QueryTypePromQL:
		return nil
	default:
		return fmt.Errorf("invalid query type: %s", q)

View on GitHub (pinned to 5069bf80b0)

Solutions

Use one of the exact constants: ReduceToOperatorLast, ReduceToOperatorSum, ReduceToOperatorAvg, ReduceToOperatorMin, ReduceToOperatorMax (strings "last", "sum", "avg", "min", "max")
Substitute "avg" for mean/expected-value intents and "last" for gauge-style current-value intents
Align frontend and backend versions so the reduce options offered in the UI match the server enum

Example fix

// before
bq.ReduceTo = v3.ReduceToOperator("mean")

// after
bq.ReduceTo = v3.ReduceToOperatorAvg

Defensive patterns

Strategy: validation

Validate before calling

switch v3.ReduceToOperator(rt) { case v3.ReduceToOperatorLast, v3.ReduceToOperatorSum, v3.ReduceToOperatorAvg, v3.ReduceToOperatorMin, v3.ReduceToOperatorMax: default: return errors.New("invalid reduceTo") }

Type guard

func isValidReduceTo(r v3.ReduceToOperator) bool { switch r { case v3.ReduceToOperatorLast, v3.ReduceToOperatorSum, v3.ReduceToOperatorAvg, v3.ReduceToOperatorMin, v3.ReduceToOperatorMax: return true }; return false }

Prevention

Map UI reduce options to the five enum values before building requests
Default to ReduceToOperatorLast when the user hasn't chosen

When it happens

Trigger: Setting BuilderQuery.ReduceTo on a v3 builder query to anything other than "last", "sum", "avg", "min", or "max" — e.g. "median", "mean", "p50", or an empty string — then calling CompositeQuery.Validate() via a query API.

Common situations: UI version mismatch where the frontend offers a reduce function the backend doesn't support, hand-written API payloads using statistical terms not in the enum, or forgetting to set ReduceTo at all when it is required.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

AI-assisted analysis of SigNoz/signoz@5069bf80b0 (2026-08-28). Data as JSON: /api/errors/eb1581710ce2b6bd. Report an issue: GitHub.