@Override
    public String toString() {
        return "fast lookup context for ranking expression '" + rankingExpressionName +
                "' [" + size() + " variables]";
    }
Perform a fast lookup directly of the value as a double. This is faster than get(index).asDouble()
searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/AbstractArrayContext.java