SigNoz/signoz · error

expected float64, got %T

Error message

expected float64, got %T

What it means

During formula evaluation in postprocess, after applying a formula function to series values the result is asserted to be float64. If the formula's expression or a custom function returns a non-float (string, nil, etc.), joinAndCalculate fails with the observed Go type.

Source

Thrown at pkg/query-service/postprocess/formula.go:146

		for _, v := range expression.Vars() {
			if _, ok := values[v]; !ok {
				canEval = false
			}
		}

		if !canEval {
			// not enough values for expression evaluation
			continue
		}

		newValue, err := expression.Evaluate(values)
		if err != nil {
			return nil, err
		}

		val, ok := newValue.(float64)
		if !ok {
			return nil, fmt.Errorf("expected float64, got %T", newValue)
		}

		if math.IsNaN(val) || math.IsInf(val, 0) {
			continue
		}

		resultSeries.Points = append(resultSeries.Points, v3.Point{
			Timestamp: timestamp,
			Value:     val,
		})
	}
	return resultSeries, nil
}

// Main function to process the Results
// A series can be "join"ed with other series if they have the same label set or one is a subset of the other.
// 1. Find all unique label sets
// 2. For each unique label set, find a series that matches the label set from each query result

View on GitHub (pinned to 5069bf80b0)

Solutions

1. Simplify the formula to isolate which expression produces the non-float value
2. Ensure all series referenced in the formula are numeric and present (no missing series)
3. Update SigNoz so formula handling matches the frontend's formula grammar

// Ensure all series used in the formula are numeric before querying
for _, s := range series { if s.Values == nil { return errors.New("missing series for formula") } }

func isFloat64(v interface{}) bool { _, ok := v.(float64); return ok }

res, err := qs.processResults(q)
if err != nil {
  if strings.Contains(err.Error(), "expected float64") { return nil, fmt.Errorf("formula produced non-numeric output; check expression %q", formula) }
  return nil, err
}

When it happens

Trigger: A query with a formula whose evaluation yields a non-numeric value — e.g. a formula referencing a string column, a function returning nil, or NaN-producing expressions that escape as other types through custom formula funcs.

Common situations: Complex formulas mixing series of different types, version mismatches where a formula function's return type changed, or division producing nil in some row implementations.

Related errors

• cannot join the given group keys
• timeShiftBy param should be a number
• alpha param should be a float
• threshold param should be a float
• invalid data type, expected string, got %v

AI-assisted analysis of SigNoz/signoz@5069bf80b0 (2026-08-28). Data as JSON: /api/errors/438e96b091bee739. Report an issue: GitHub.