**How to reproduce**

CH version: `20.5.2 revision 54435` (latest on `apt` at the moment). Cannot reproduce on `20.4.5`, so it's a regression.

Table:

```sql
create table repro_hits (
    date Date,
    metric Float64
) engine=MergeTree() order by date
```

Query:

```sql
SELECT
    date as period,
    1 as having_check,
    min(date) as period_start,
    addDays(max(date), 1) as period_end,
    dateDiff('second', period_start, period_end) as total_duration,
    sum(metric) as metric_
FROM repro_hits
GROUP BY period
having having_check != -1
```

**Error message and/or stacktrace**
```
Received exception from server (version 20.5.2):
Code: 179. DB::Exception: Received from localhost:9000. DB::Exception: Different expressions with the same alias period_start:
min(date) AS period_start
and
date AS period_start
.
```

The error goes away if I opt out of optimization with `SETTINGS enable_optimize_predicate_expression = 0`.
{
    DuplicateOrderByVisitor::Data order_by_data{context};
    DuplicateOrderByVisitor(order_by_data).visit(query);
}
const ASTSelectQuery * getSimpleSubselect(const ASTSelectQuery & select)
{
    if (!select.tables())
        return nullptr;
    const auto & tables = select.tables()->children;
    if (tables.empty() || tables.size() != 1)
        return nullptr;
    const auto & ast_table_expression = tables[0]->as<ASTTablesInSelectQueryElement>()->table_expression;
    if (!ast_table_expression)
        return nullptr;
    const auto & table_expression = ast_table_expression->as<ASTTableExpression>();
    if (!table_expression->subquery)
        return nullptr;
    const auto & subquery = table_expression->subquery->as<ASTSubquery>();
    if (!subquery || subquery->children.size() != 1)
        return nullptr;
    const auto & subselect_union = subquery->children[0]->as<ASTSelectWithUnionQuery>();
    if (!subselect_union || !subselect_union->list_of_selects ||
        subselect_union->list_of_selects->children.size() != 1)
        return nullptr;
    const auto & subselect = subselect_union->list_of_selects->children[0]->as<ASTSelectQuery>();
    if (subselect && subselect->settings())
        return nullptr;
    return subselect;
}
std::unordered_set<String> getDistinctNames(const ASTSelectQuery & select)