@Override
    public Set<String> names() {
        return indexedBindings.names();
    }
Create a fast lookup context for an expression.
This instance should be reused indefinitely by a single thread.

@param expression the expression to create a context for
@param ignoreUnknownValues whether attempts to put values not present in this expression
                           should fail (false - the default), or be ignored (true)
searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/AbstractArrayContext.java