**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`.
{
    if (!select.select() || select.select()->children.empty())
        return;
    const ASTSelectQuery * subselect = getSimpleSubselect(select);
    if (!subselect)
        return;
    std::unordered_set<String> distinct_names = getDistinctNames(*subselect);
    std::unordered_set<String> selected_names;
    
    for (const auto & id : select.select()->children)
    {
        const auto * identifier = id->as<ASTIdentifier>();
        if (!identifier)
            return;
        String name = identifier->shortName();
        if (!distinct_names.count(name))
            return; 
        selected_names.insert(name);
    }
    
    
    if (selected_names.size() != distinct_names.size())
        return;
    select.distinct = false;
}
void optimizeMonotonousFunctionsInOrderBy(ASTSelectQuery * select_query, const Context & context,
                                          const TablesWithColumns & tables_with_columns)
{
    auto order_by = select_query->orderBy();