message: Use approx_count_distinct after all
diff: @@ -33,14 +33,6 @@ static unique_ptr<ParsedExpression> SummarizeCreateCountStar() {
  return move(aggregate_function);
  }
  -static unique_ptr<ParsedExpression> SummarizeCreateCountUnique(string column_name) {
  - vector<unique_ptr<ParsedExpression>> children;
  - children.push_back(make_unique<ColumnRefExpression>(move(column_name)));
  - auto aggregate_function = make_unique<FunctionExpression>("count", move(children));
  - aggregate_function->distinct = true;
  - return move(aggregate_function);
  -}
  -
  static unique_ptr<ParsedExpression> SummarizeCreateBinaryFunction(const string &op, unique_ptr<ParsedExpression> left,
  unique_ptr<ParsedExpression> right) {
  vector<unique_ptr<ParsedExpression>> children;
  @@ -87,7 +79,7 @@ BoundStatement Binder::BindSummarize(ShowStatement &stmt) {
  type_children.push_back(make_unique<ConstantExpression>(Value(plan.types[i].ToString())));
  min_children.push_back(SummarizeCreateAggregate("min", plan.names[i]));
  max_children.push_back(SummarizeCreateAggregate("max", plan.names[i]));
  - unique_children.push_back(SummarizeCreateCountUnique(plan.names[i]));
  + unique_children.push_back(SummarizeCreateAggregate("approx_count_distinct", plan.names[i]));
  avg_children.push_back(plan.types[i].IsNumeric() ? SummarizeCreateAggregate("avg", plan.names[i])
  : make_unique<ConstantExpression>(Value()));
  count_children.push_back(SummarizeCreateCountStar());
  @@ -101,7 +93,7 @@ BoundStatement Binder::BindSummarize(ShowStatement &stmt) {
  select_node->select_list.push_back(SummarizeWrapUnnest(type_children, "column_type"));
  select_node->select_list.push_back(SummarizeWrapUnnest(min_children, "min"));
  select_node->select_list.push_back(SummarizeWrapUnnest(max_children, "max"));
  - select_node->select_list.push_back(SummarizeWrapUnnest(unique_children, "unique"));
  + select_node->select_list.push_back(SummarizeWrapUnnest(unique_children, "approx_unique"));
  select_node->select_list.push_back(SummarizeWrapUnnest(avg_children, "avg"));
  select_node->select_list.push_back(SummarizeWrapUnnest(count_children, "count"));
  select_node->select_list.push_back(SummarizeWrapUnnest(null_percentage_children, "null_percentage"));
  