No rows returned by fetch() when for DELETE rewritten to UPDATE using rule

Chưa có ai nhận issue này.

* **asyncpg version**: 0.29.0
* **PostgreSQL version**: 16.2 (`postgres:latest` Docker image)
* **Python version**: 3.12.3
* **Platform**: Tested on macOS and Linux
* **Do you use pgbouncer?**: No
* **Did you install asyncpg with pip?**: Yes
* **Can the issue be reproduced under both asyncio and [uvloop](https://github.com/magicstack/uvloop)?**: Yes

Unexpected behaviour: It seems `asyncpg` doesn't return the rows returned by a DELETE query rewritten to an UPDATE query by a rule. Perhaps because it's optimizing (the query status is `DELETE 0`, so perhaps it thinks it doesn't need to return any rows) or something like that? I didn't dive in any further to check if that is indeed what is happening.

Reproduction

```py
import asyncio
import asyncpg

async def main():
connection = await asyncpg.connect('postgresql://postgres:password@localhost/test')

async def fetch_print(query, *params):
result = await connection.fetch(query, *params)
i = 0
for row in result:
print(f' - {row}')
i += 1
if i == 0:
print(' (no rows returned)')
print('')

# Create table with rule for deletion
await connection.execute('''
CREATE TABLE items (
id serial PRIMARY KEY,
name text UNIQUE,
deleted boolean DEFAULT false
);
CREATE RULE softdelete AS
ON DELETE
TO items
DO INSTEAD
UPDATE items SET deleted = true WHERE id = OLD.id RETURNING OLD.*
;
INSERT INTO items (name) VALUES
('foo'),
('bar')
;
''')

print('Our table has a rule that updates the "deleted" column instead of deleting the row.\n')

# Show contents
print('We start with 2 rows which are not soft-deleted:')
await fetch_print('SELECT * FROM items')

# Try delete (the unexpected case)
print('Deleting with RETURNING should give us a row (it does in psql), but we do not get any in asyncpg:')
await fetch_print('''
DELETE FROM items WHERE name = $1 RETURNING id
''', 'foo')

# Confirm above query worked
print('But the row is now soft-deleted:')
await fetch_print('SELECT * FROM items')

# Workaround
print('If wrapped in a CTE it does work:')
await fetch_print('''
WITH x AS (
DELETE FROM items WHERE name = $1 RETURNING id
) SELECT * FROM x
''', 'bar')

# Confirm above query worked
print('And it is again properly softdeleted:')
await fetch_print('SELECT * FROM items')

print('We now delete the rule.\n')
await connection.execute('DROP RULE softdelete ON items')

# Confirm normal delete without rule returns rows
print('Normal deletion (without the rule) does return rows correctly:')
await fetch_print('''
DELETE FROM items RETURNING id
''')

# Confirm above query worked
print('And now both rows are indeed gone:')
await fetch_print('SELECT * FROM items')

# Clean up table after we are done
await connection.execute('DROP TABLE items')

await connection.close()

asyncio.run(main())
```

Output of reproduction

```
Our table has a rule that updates the "deleted" column instead of deleting the row.

We start with 2 rows which are not soft-deleted:
-
-

Deleting with RETURNING should give us a row (it does in psql), but we do not get any in asyncpg:
(no rows returned)

But the row is now soft-deleted:
-
-

If wrapped in a CTE it does work:
-

And it is again properly softdeleted:
-
-

We now delete the rule.

Normal deletion (without the rule) does return rows correctly:
-
-

And now both rows are indeed gone:
(no rows returned)

```

In contrast the `psql` command line tool *does* show me the resulting rows when the result code is `DELETED 0`.

Output of psql

```
test=# DELETE FROM items WHERE name = 'foo' RETURNING id;
id
----
1
(1 row)

DELETE 0
```

So it is a bit unexpected that `asyncpg` doesn't return any rows.

Bắt đầu bằng cách chạy bản tái hiện bằng Python trong issue trên PostgreSQL 16.2, so sánh DELETE có RETURNING được viết lại bởi rule, workaround bằng CTE và DELETE thông thường. Theo dõi kết quả fetch của asyncpg đối với truy vấn được viết lại trực tiếp; hoàn tất khi truy vấn trả về hàng được psql hiển thị mà vẫn giữ nguyên hành vi hiện có cho các trường hợp khác.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.