Set<Attribute> findAliases(List<NamedExpression> projectList) {
            return mapToSet(projectList, e -> e instanceof Alias ? e.toAttribute() : null, true);
        }
Foreach expression, expands the matching attribute.*'s in `child`'s input for the subtree
rooted at each expression.
indexr-query-opt/src/main/java/io/indexr/query/Analyzer.java