dgraph-io/dgraph · error

empty variable name in function call

Error message

empty variable name in function call

What it means

Error raised by the RDF parser in chunker/rdf_parser.go when a function call references a variable with an empty name (e.g. fn with no variable identifier). Indicates malformed input; fix by providing the variable name inside the function call.

Source

Thrown at chunker/rdf_parser.go:248

}

// 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")
	}
	item := it.Item()
	if item.Typ != itemLeftRound {
		return fmt.Errorf("expected '(' but found %v at facet", item.Val)

View on GitHub (pinned to 759e242be6)

Solutions

1. Supply a real variable name inside the parentheses.
2. Fix the template/generator so the variable placeholder is populated before calling ParseRDF.
3. Strip or skip lines whose function calls have empty variables before parsing.

Example fix

// before
ParseRDF(fmt.Sprintf("<s> <p> uid(%s) .", varName))  // varName == ""
// after
if varName == "" { return errors.New("varName required") }
ParseRDF(fmt.Sprintf("<s> <p> uid(%s) .", varName))

if strings.TrimSpace(varName) == "" {
	return errors.New("variable name must be non-empty")
}

if _, err := parseFunction(it); err != nil {
	if err.Error() == "empty variable name in function call" {
		return fmt.Errorf("populate variable placeholder before parsing: %w", err)
	}
	return err
}

When it happens

Trigger: ParseRDF input where a function call's parentheses contain only whitespace or a token that trims to the empty string, e.g. 'uid( )' or 'uid(\t)'.

Common situations: Templated queries where the variable placeholder was never filled in; generators emitting empty placeholders; accidental deletion of the variable during editing.

Related errors

• NQuad failed sanity check. Subject: %q, Predicate: %q, Objec
• empty facetKeys not allowed
• expected '(', found: %s
• expected variable name, found: %s
• expected ')', found: %s

AI-assisted analysis of dgraph-io/dgraph@759e242be6 (2026-09-01). Data as JSON: /api/errors/c7cae88c00809efc. Report an issue: GitHub.