What causes "expected variable name, found: %s" in dgraph-io/dgraph?

Put a valid variable name inside the parentheses, e.g. uid(var).

expected variable name, found: %s

Error message

expected variable name, found: %s

What it means

Error raised by the RDF/N-Quads parser in chunker/rdf_parser.go when parsing a variable (e.g. in a _var_ context) and the next token is not a valid variable name. The offending token is included via %s. Indicates malformed input; fix by supplying a valid variable name in the RDF data.

Source

Thrown at chunker/rdf_parser.go:245

	}

	return rnq, nil
}

// parseFunction parses uid(<var name>) and returns
// uid(<var name>) after striping whitespace if any
func parseFunction(it *lex.ItemIterator) (string, error) {
	item := it.Item()
	s := item.Val

	it.Next()
	if item = it.Item(); item.Typ != itemLeftRound {
		return "", fmt.Errorf("expected '(', found: %s", item.Val)
	}

	it.Next()
	if item = it.Item(); item.Typ != itemVarName {
		return "", fmt.Errorf("expected variable name, found: %s", item.Val)
	}
	if strings.TrimSpace(item.Val) == "" {
		return "", errors.New("empty variable name in function call")
	}
	s += "(" + item.Val + ")"

	it.Next()
	if item = it.Item(); item.Typ != itemRightRound {
		return "", fmt.Errorf("expected ')', found: %s", item.Val)
	}

	return s, nil
}

func parseFacetsRDF(it *lex.ItemIterator, rnq *api.NQuad) error {
	if !it.Next() {
		return errors.New("unexpected end of facets")
	}

View on GitHub (pinned to 759e242be6)

Solutions

Put a valid variable name inside the parentheses, e.g. uid(var).
If you meant to pass a value, use the syntax supported for that function instead of a bare literal.
Check the input line for truncation that removed the variable token.

Example fix

// before
ParseRDF("<s> <p> uid() .")
// after
ParseRDF("<s> <p> uid(var) .")

Defensive patterns

Strategy: validation

Validate before calling

func hasVariable(fn string) bool {
	open := strings.Index(fn, "(")
	close := strings.LastIndex(fn, ")")
	return open >= 0 && close > open+1 && strings.TrimSpace(fn[open+1:close]) != ""
}

Try / catch

if _, err := parseFunction(it); err != nil {
	if strings.HasPrefix(err.Error(), "expected variable name") {
		return fmt.Errorf("function call requires exactly one variable: %w", err)
	}
	return err
}

Prevention

Never emit empty function calls; always pass a variable.
Use the query-language syntax for literal values instead of functions.
Validate generated function expressions against a name(variable) regex.

When it happens

Trigger: ParseRDF input with a function call containing something other than a variable between the parentheses, e.g. 'uid()' with nothing inside, or 'uid(0x123)' passing a literal UID instead of a variable.

Common situations: Empty function calls copied from templates; passing raw values where a variable is required; lexer splitting a complex expression into non-variable tokens.

Related errors

AI-assisted analysis of dgraph-io/dgraph@759e242be6 (2026-09-01). Data as JSON: /api/errors/23502bf2b6c76a41. Report an issue: GitHub.