Re: Should we optimize the `ORDER BY random() LIMIT x` case?

[Andrei Lepikhov]

On 5/19/25 12:25, Aleksander Alekseev wrote:
```
-- imagine replacing inefficient array_sample(array_agg(t), 10)
-- with more efficient array_sample_reservoir(t, 10)
SELECT (unnest(agg)).* AS k FROM
(  SELECT array_sample(array_agg(t), 10) AS agg FROM (
    ... here goes the subquery ...
    ) AS t
);
```
... if only we supported such a column expansion for not registered
records. Currently such a query fails with:

```
ERROR:  record type has not been registered
```
I know about this issue. Having resolved it in a limited number of local 
cases (like FDW push-down of row types), I still do not have a universal 
solution worth proposing upstream. Do you have any public implementation 
of the array_sample_reservoir to play with?

--
regards, Andrei Lepikhov