mpurins opened a new issue, #15734:
URL: https://github.com/apache/datafusion/issues/15734
### Describe the bug
Hello, it seems that there is inconsistent behaviour for select queries with
group by on constant when there are no input rows.
When I have no aggregation functions then result of such query is empty, but
as soon as I add some aggregation function I get single row result.
### To Reproduce
Run following query in datafusion-cli
```
> select 'wat' as key, count(1) as count from (select * from
unnest(array[]::text[])) as b(field) group by key;
+-----+-------+
| key | count |
+-----+-------+
| wat | 0 |
+-----+-------+
1 row(s) fetched.
Elapsed 0.004 seconds.
```
### Expected behavior
Empty result
### Additional context
Query with no aggregation functions gives empty result
```
DataFusion CLI v46.0.1
> select 'wat' as key from (select * from unnest(array[]::text[])) as
b(field) group by key;
+-----+
| key |
+-----+
+-----+
0 row(s) fetched.
Elapsed 0.004 seconds.
```
Postgres gives empty results in both cases
```
psql (17.4 (Homebrew))
Type "help" for help.
postgres=# select 'wat' as key from (select * from unnest(array[]::text[]))
as b(field) group by key;
key
-----
(0 rows)
postgres=# select 'wat' as key, count(1) as count from (select * from
unnest(array[]::text[])) as b(field) group by key;
key | count
-----+-------
(0 rows)
```
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