prestodb/presto · error · IllegalArgumentException

Expected exactly one parameter for VARCHAR

Error message

Expected exactly one parameter for VARCHAR

What it means

VARCHAR in Presto is parametric: it takes either zero parameters (unbounded) or exactly one length parameter. This IllegalArgumentException is thrown at type-creation time when the type manager receives a VARCHAR type signature with two or more parameters, e.g. VARCHAR(10, 20).

Solutions

1. Fix the type signature to use VARCHAR(n) with exactly one parameter, or plain VARCHAR for unbounded.
2. Search the connector/plugin metadata or DDL generator emitting the signature and correct the string formatting.
3. Validate signature strings in tests before registering custom types.

Example fix

// before
TypeSignature sig = parseSignature("VARCHAR(10, 20)");
// after
TypeSignature sig = parseSignature("VARCHAR(10)");

boolean isValidVarcharSignature(List<TypeParameter> params) {
    return params.isEmpty() || params.size() == 1;
}

try {
    Type t = typeManager.getType(parseSignature(sigString));
} catch (IllegalArgumentException e) {
    if (e.getMessage().contains("Expected exactly one parameter for VARCHAR")) {
        // fall back to unbounded VARCHAR
    }
}

When it happens

Trigger: Registering or resolving a type signature like VARCHAR(a, b) — more than one type parameter supplied to VARCHAR in DDL, a connector/plugin TypeSignature, or a serialized plan referencing a malformed VARCHAR signature.

Common situations: Hand-written connector metadata with a wrong type signature string, code-generated DDL, query rewrite tools that duplicate parameters, plugin version mismatches producing malformed signatures.

Related errors

• Invalid VARCHAR length
• VARCHAR length must be a number
• CHAR length must be a number
• Expected at most one parameter for CHAR
• TIMESTAMP precision must be in range

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/c9676cb5f3eefea7. Report an issue: GitHub.

Appendix: source

Thrown at presto-main-base/src/main/java/com/facebook/presto/type/VarcharParametricType.java:44

public class VarcharParametricType
        implements ParametricType
{
    public static final VarcharParametricType VARCHAR = new VarcharParametricType();

    @Override
    public String getName()
    {
        return StandardTypes.VARCHAR;
    }

    @Override
    public Type createType(List<TypeParameter> parameters)
    {
        if (parameters.isEmpty()) {
            return createUnboundedVarcharType();
        }
        if (parameters.size() != 1) {
            throw new IllegalArgumentException("Expected exactly one parameter for VARCHAR");
        }

        TypeParameter parameter = parameters.get(0);

        if (!parameter.isLongLiteral()) {
            throw new IllegalArgumentException("VARCHAR length must be a number");
        }

        long length = parameter.getLongLiteral();

        if (length == VarcharType.UNBOUNDED_LENGTH) {
            return VarcharType.createUnboundedVarcharType();
        }

        if (length < 0 || length > VarcharType.MAX_LENGTH) {
            throw new IllegalArgumentException("Invalid VARCHAR length " + length);
        }

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