Allow parentheses in GROUP BY

[yuval-illumex]

In TrinoDB, GROUP BY Can have parentheses with multiple values.

Example Query:

SELECT orderstatus,orderpriority,COUNT(*)
FROM tpch.sf1.orders 
GROUP BY (orderstatus,orderpriority)
LIMIT 10;

[alamb]

thank you for the contribution -- sorry for the delay in response @yuval-illumex

So I was playing around with postgres and there is a difference between col1, col2 and (col1, col2). Specifically, I think (col1, col2) is treated as some tuple type.

I think this PR effectively strips off the parenthesis

alamb=# select (t1_id, t1_name), count(*) from t1 group by (t1_id, t1_name);
  row   | count 
--------+-------
 (44,d) |     1
 (77,e) |     1
 (11,a) |     1
 (22,b) |     1
 (33,c) |     1
(5 rows)

alamb=# select t1_id, t1_name, count(*) from t1 group by t1_id, t1_name;
 t1_id | t1_name | count 
-------+---------+-------
    44 | d       |     1
    77 | e       |     1
    11 | a       |     1
    22 | b       |     1
    33 | c       |     1
(5 rows)

Turns out that mysql just rejects this syntax

mysql> select (t1_id, t1_name), count(*) from t1 group by (t1_id, t1_name);
ERROR 1241 (21000): Operand should contain 1 column(s)

I didn't catch it quite in time, but the same thing is true for distinct: #391

I don't have a trino installation around to test -- what does trino do with the syntax above?

[yuval-illumex]

Thanks @alamb

The following syntax works in Trino:

This is the default schemas and tables coming with tirno, so you can tun Trino with docker to play with using this query.

I'm more worried about GroupBy rather then Select - I think the parentheses are more common in GroupBy (and Distinct)
If this PR is a problem. I would love to find a way to make it work in Groupby/Distinct

[alamb]

Thanks @yuval-illumex -- it looks to me like in this case too Trino is treating GROUP BY (a, b) as GROUP BY {set_expr} while the change in this PR effectively ignores the parenthesis and treats GROUP BY (a, b) as GROUP BY a, b

[alamb]

@yuval-illumex can you please look into parsing GROUP BY (a, b) as a tuple / row expr?
https://trino.io/docs/current/language/types.html?highlight=data%20type#row

I think you may be able to parse_tuple: use https://github.com/sqlparser-rs/sqlparser-rs/blob/2614576dbf140824cb659bcc7026b21bd1b82f0a/src/parser.rs#L652

[yuval-illumex]

@alamb parse_tuple do works, but I could use some help.
I don't understand how it goes with parse_group_by_expr:
https://github.com/sqlparser-rs/sqlparser-rs/blob/2614576dbf140824cb659bcc7026b21bd1b82f0a/src/parser.rs#L623

It parses expressions, and I'm not sure how to identify when it should be an expression and when should it be a tuple. as the function must return an expression.

[alamb]

@alamb parse_tuple do works, but I could use some help.

Looking into it

[alamb]

@yuval-illumex this is what I had in mind (it should cover all paren cases): #414

[alamb]

Probably not needed after #414