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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2021/04/06 10:26:58 UTC
[GitHub] [arrow] alamb commented on a change in pull request #9897: ARROW-12214: [Rust][DataFusion] Add tests for limit
alamb commented on a change in pull request #9897:
URL: https://github.com/apache/arrow/pull/9897#discussion_r607728739
##########
File path: rust/datafusion/src/execution/context.rs
##########
@@ -1721,6 +1721,46 @@ mod tests {
Ok(())
}
+ #[tokio::test]
+ async fn limit() -> Result<()> {
+ let tmp_dir = TempDir::new()?;
+ let mut ctx = create_ctx(&tmp_dir, 1)?;
+ ctx.register_table("t", table_with_sequence(1, 1000).unwrap())
Review comment:
I am not sure --- I have a program (https://github.com/influxdata/influxdb_iox/pull/1117) that I made for testing some stuff as we roll out IOx and there is definitely a problem with limit, though I haven't figured out if it is a problem in DataFusion or not
For this plan:
```
> explain select * from chunks limit 1;
+--------------+-----------------------------------------------------------------------------------------------------------------------------------------+
| plan_type | plan |
+--------------+-----------------------------------------------------------------------------------------------------------------------------------------+
| logical_plan | Limit: 1 |
| | Projection: #database_name, #id, #partition_key, #storage, #estimated_bytes, #time_of_first_write, #time_of_last_write, #time_closing |
| | TableScan: chunks projection=None |
+--------------+-----------------------------------------------------------------------------------------------------------------------------------------+
1 rows in set. Query took 0 seconds.
```
Produces no rows (and no columns) when there is a limit:
```
> select * from chunks limit 1;
++
||
++
++
0 rows in set. Query took 0 seconds.
```
But there is definitely data in that table:
```
> select * from chunks;
+-----------------------------------+-----+---------------------+---------------------+-----------------+-------------------------------+-------------------------------+-------------------------------+
| database_name | id | partition_key | storage | estimated_bytes | time_of_first_write | time_of_last_write | time_closing |
+-----------------------------------+-----+---------------------+---------------------+-----------------+-------------------------------+-------------------------------+-------------------------------+
| 844910ece80be8bc_05a7a51565539000 | 0 | 2021-04-05 21:00:00 | OpenMutableBuffer | 259733 | 2021-04-05 21:29:38.978576237 | 2021-04-05 21:49:47.995408514 | |
....
| 844910ece80be8bc_eaec8df57a81a1e9 | 1 | 2021-04-05 21:00:00 | OpenMutableBuffer | 6408933 | 2021-04-05 21:44:31.507950286 | 2021-04-05 21:55:37.226659960 | |
+-----------------------------------+-----+---------------------+---------------------+-----------------+-------------------------------+-------------------------------+-------------------------------+
226 rows in set. Query took 0 seconds.
```
I am still looking into it
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