What causes "Wrong type %v encountered for func %%" in dgraph-io/dgraph?

Declare the predicate as int (or float) in the schema

Wrong type %v encountered for func %%

Error message

Wrong type %v encountered for func %%

What it means

applyMod returns this error when a modulo (%%) operand has DEFAULT type. Modulo is only defined for int and float typed values in Dgraph's math engine; a DEFAULT type id means the operand carried no usable type. Division-by-zero is reported separately as ErrorDivisionByZero.

Source

Thrown at query/aggregator.go:331

}

func applyMod(a, b, c *types.Val) error {
	vBase := getValType(a)
	switch vBase {
	case INT:
		if b.Value.(int64) == 0 {
			return ErrorDivisionByZero
		}
		c.Value = a.Value.(int64) % b.Value.(int64)

	case FLOAT:
		if b.Value.(float64) == 0 {
			return ErrorDivisionByZero
		}
		c.Value = math.Mod(a.Value.(float64), b.Value.(float64))

	case DEFAULT:
		return errors.Errorf("Wrong type %v encountered for func %%", a.Tid)
	}
	return nil
}

func applyPow(a, b, c *types.Val) error {
	vBase := getValType(a)
	switch vBase {
	case INT:
		c.Value = math.Pow(float64(a.Value.(int64)), float64(b.Value.(int64)))
		c.Tid = types.FloatID

	case FLOAT:
		// Fractional power of -ve numbers should not be returned.
		if a.Value.(float64) < 0 &&
			math.Abs(math.Ceil(b.Value.(float64))-b.Value.(float64)) > 0 {
			return ErrorFractionalPower
		}
		c.Value = math.Pow(a.Value.(float64), b.Value.(float64))

View on GitHub (pinned to 759e242be6)

Solutions

Declare the predicate as int (or float) in the schema
Ensure the stored values are actually numeric; re-set malformed values
Filter out nodes with missing values before the modulo expression

Example fix

// before
math(a % 10) // a untyped
// after
// schema: a: int .
math(a % 10)

Defensive patterns

Strategy: validation

Validate before calling

func isModOperand(v types.Val) bool {
    t := getValType(&v)
    return t == INT || t == FLOAT
}

Type guard

func canMod(a, b types.Val) bool {
    return isModOperand(a) && isModOperand(b) && a.Value.(float64) != 0 || getValType(&a) == INT
}

Try / catch

if err := applyMod(a, b, c); err != nil {
    if strings.Contains(err.Error(), "func %") {
        return fmt.Errorf("operand type %v not supported for %%; declare as int", a.Tid)
    }
    return err // includes ErrorDivisionByZero
}

Prevention

Declare int/float schema types for predicates used with %
Guard against zero divisors before modulo
Filter out missing values before bucketing expressions
Keep bucketing math on int-typed predicates

When it happens

Trigger: math("%", a, b) evaluates where an operand's Tid is DEFAULT — untyped predicate values, empty data, or values whose earlier conversion failed silently.

Common situations: Modulo over an untyped or uid predicate; bucketing (e.g. mod 10) on values that failed to load; missing schema declarations on computed fields.

Related errors

AI-assisted analysis of dgraph-io/dgraph@759e242be6 (2026-09-01). Data as JSON: /api/errors/a8850ce1514e5eb4. Report an issue: GitHub.