map_from_entries: empty subquery returns null map

[maingoh]

Describe the bug

I couldn't create a sample as I don't know how to how to create an empty array of rows. But a query like below return a null map when the subquery return no rows. I expected it to return an empty map instead.

Also, couldn't we simplify the syntax by removing the explicit array() ?

Error message/log

No response

To Reproduce

select map_from_entries(array(select row(foo.id, foo.name) from foo where foo.id=unrelated.id))

Expected behavior

Return an empty map instead of null

How did you deploy RisingWave?

No response

The version of RisingWave

version | PostgreSQL 13.14.0-RisingWave-2.0.4 (2d75798)

Additional context

No response

[xxchan]

It seems to return empty map, instead of null:

dev=> select * from t;
┌───┐
│ x │
├───┤
└───┘
(0 rows)

dev=> select map_from_entries( array( select row(x,x) from t ));
┌──────────────────┐
│ map_from_entries │
├──────────────────┤
│ {}               │
└──────────────────┘
(1 row)

Could you provide a reproduciable example?