Hello, there. Run into the problem with DISTINCT expression. It works incorrectly on the main query if it was already applied to one of the subqueries bond with UNION ALL.

**How to reproduce**
Server version: 20.5.4.40. 19.17.6.36 was free of the bug.
Using Datagrip for running queries.
Non-default settings:
```
input_format_defaults_for_omitted_fields: 1
decimal_check_overflow: 0
joined_subquery_requires_alias: 0
```

Consider following query
```
select distinct number
from ((select number from numbers(10)) union all (select number from numbers(20)));
```
It works fine, returning 20 rows as expected.

But if we add distinct to subqueries (it doesn't matter to the first, the second or both)
```
select distinct number
from ((select distinct number from numbers(10)) union all (select distinct number from numbers(20)));
```

Then in 20.5.4.40 we'll see 30 rows with numbers from 0 to 9 duplicated.
However, `count(distinct number)` returns the correct number of rows.

{
        if (!select_query.distinct || !select_query.select())
            return;
        
        for (const auto & elem : select_query.children)
        {
            if (elem->as<ASTSetQuery>() && !elem->as<ASTSetQuery>()->is_standalone)
                return;
        }
        auto expression_list = select_query.select();
        std::vector<String> current_ids;
        if (expression_list->children.empty())
            return;
        current_ids.reserve(expression_list->children.size());
        for (const auto & id : expression_list->children)
            current_ids.push_back(id->getColumnName());
        if (data.is_distinct && current_ids == data.last_ids)
            select_query.distinct = false;
        data.is_distinct = true;
        data.last_ids = std::move(current_ids);
    }
    static bool needChildVisit(const ASTPtr &, const ASTPtr &)
    {
        return true;
    }
};
using DuplicateDistinctVisitor = InDepthNodeVisitor<DuplicateDistinctMatcher, false>;
}