@Override
    public DataType setInputType(DataType inputType, TypeContext context) {
        super.setInputType(inputType, DataType.STRING, context);
        return getOutputType(context); // Can not infer int or long
    }
Hashes a string value to a long or int (by type inference on the target value).

@author bratseth
indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/HashExpression.java