apache/cassandra · error · IllegalArgumentException

Function does not declare an argument with index

Error message

Function does not declare an argument with index ${index}

What it means

getArgumentTypeByIndex validates that the requested index exists in the function's declared argument list; if the index is negative or >= the number of arguments, an IllegalArgumentException is thrown. It backs newArgUDTValue and newArgTupleValue in UDFContextImpl.

Solutions

Use an index within 0..(number of declared arguments - 1)
Prefer the by-name variant (newArgUDTValue("arg_name")) to avoid index drift when signatures change
Update the UDF code whenever the CREATE FUNCTION argument list changes

Example fix

// before (3-arg function)
TupleValue tv = context.newArgTupleValue(3); // out of range
// after
TupleValue tv = context.newArgTupleValue(2); // last valid index

Defensive patterns

Strategy: validation

Validate before calling

// Validate index against the declared argument count:
if (index < 0 || index >= argTypes.size()) throw new IndexOutOfBoundsException("no arg at index " + index);

Type guard

boolean hasArg(int i, int argCount) { return i >= 0 && i < argCount; }

Try / catch

try { TupleValue tv = ctx.newArgTupleValue(i); }
catch (IllegalArgumentException e) {
  if (e.getMessage().contains("does not declare an argument")) { /* clamp index or use by-name lookup */ }
  else throw e;
}

Prevention

Prefer by-name accessors (newArgTupleValue("name")) over indices
Re-verify hard-coded indices whenever the function signature changes

When it happens

Trigger: Calling udfContext.newArgTupleValue(i) or newArgUDTValue(i) with an index outside [0, argCount) — e.g. index 3 in a 3-argument function, or a negative index.

Common situations: Off-by-one errors after changing the function's argument list; hard-coded indices that no longer match CREATE FUNCTION; loops using argCount instead of argCount-1.

Related errors

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/19855db0c631170f. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/cql3/functions/UDFContextImpl.java:136

    {
        if (!(dataType instanceof UserType))
            throw new IllegalStateException("Function argument is not a UDT but a " + dataType.getName());
        UserType userType = (UserType) dataType;
        return userType.newValue();
    }

    private static TupleValue newTupleValue(DataType dataType)
    {
        if (!(dataType instanceof TupleType))
            throw new IllegalStateException("Function argument is not a tuple type but a " + dataType.getName());
        TupleType tupleType = (TupleType) dataType;
        return tupleType.newValue();
    }

    private UDFDataType getArgumentTypeByIndex(int index)
    {
        if (index < 0 || index >= argTypes.size())
            throw new IllegalArgumentException("Function does not declare an argument with index " + index);
        return argTypes.get(index);
    }

    private UDFDataType getArgumentTypeByName(String argName)
    {
        UDFDataType arg = byName.get(argName);
        if (arg == null)
            throw new IllegalArgumentException("Function does not declare an argument named '" + argName + '\'');
        return arg;
    }
}

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