Improve Aggregate with Limit

[waruto210]

Is your feature request related to a problem or challenge?

Currently datafusion supports topk_aggregation(#7192 ), and I've noticed two potential areas for optimization:

1. topk_aggregation only supports ordering by aggregations (order by agg), but doesn't support ordering by columns
2. topk_aggregation cannot be used in cases where there is no order by clause

Describe the solution you'd like

1. For the first one, I think we can directly use the current priority queue solution

2. For the second one:

   The following query which without an ORDER BY clause is a non-deterministic query where returning aggregate results for any 10 keys is valid. Therefore, the simplest optimization method is to make the aggregate operation work in an ordered manner.

   SELECT "UserID", MIN("AdvEngineID") FROM hits GROUP BY "UserID" order by MIN("AdvEngineID") LIMIT 10;

   When using ORDER BY, it runs faster

   > SELECT "UserID", MIN("AdvEngineID") FROM hits GROUP BY "UserID" order by MIN("AdvEngineID") LIMIT 10;
   +---------------------+-----------------------+
   | UserID              | min(hits.AdvEngineID) |
   +---------------------+-----------------------+
   | 8265925904823819813 | 0                     |
   | 4187744066815097140 | 0                     |
   | 7970073217952173230 | 0                     |
   | 1427747163043990597 | 0                     |
   | 844431718317972727  | 0                     |
   | 5777095312382298493 | 0                     |
   | 1726996514541263413 | 0                     |
   | 9126602271142633613 | 0                     |
   | 137961262398427389  | 0                     |
   | 1015195936484711824 | 0                     |
   +---------------------+-----------------------+
   10 row(s) fetched.
   Elapsed 0.389 seconds.
   
   > SELECT "UserID", MIN("AdvEngineID") FROM hits GROUP BY "UserID" LIMIT 10;
   +--------------------+-----------------------+
   | UserID             | min(hits.AdvEngineID) |
   +--------------------+-----------------------+
   | 572919489234519776 | 0                     |
   | 573305205053433738 | 0                     |
   | 573316808606264402 | 0                     |
   | 573764012887855352 | 0                     |
   | 573878311420505425 | 0                     |
   | 574390391777319344 | 0                     |
   | 574747808491966822 | 0                     |
   | 574822330152391359 | 0                     |
   | 574882842092706724 | 0                     |
   | 576132580282803970 | 0                     |
   +--------------------+-----------------------+
   10 row(s) fetched.
   Elapsed 0.632 seconds.

Describe alternatives you've considered

No response

Additional context

Just found that the TopKAggregation only support group by one column, I'm confused.

datafusion/datafusion/physical-optimizer/src/topk_aggregation.rs

Line 57 in 0f5634e

let group_key = aggr.group_expr().expr().iter().exactly_one().ok()?;