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Posted to github@datafusion.apache.org by "2010YOUY01 (via GitHub)" <gi...@apache.org> on 2025/10/31 11:59:13 UTC
[I] Support `reduction_fator` metric (for `EXPLAIN ANALYZE`) in `AggregateExec` [datafusion]
2010YOUY01 opened a new issue, #18410:
URL: https://github.com/apache/datafusion/issues/18410
### Is your feature request related to a problem or challenge?
In the pre-aggregation stage (In datafusion's implementation, `AggregateExec` with `Partial` mode), a `reduction_factor` can be calculated as `output_rows (after partial aggregation) / input_rows` in `AggregateExec`
Background for 'partial aggregation': https://github.com/apache/datafusion/blob/e65dafe7330f0324b28d9037f4e5a73cf12e99ce/datafusion/physical-plan/src/aggregates/row_hash.rs#L303
### Example with `datafusion-cli`
```
> set datafusion.explain.analyze_level = summary;
0 row(s) fetched.
Elapsed 0.000 seconds.
> create table t1(a int, b int);
0 row(s) fetched.
Elapsed 0.007 seconds.
> insert into t1 values (1,10), (1, 20), (2,10), (2,30);
+-------+
| count |
+-------+
| 4 |
+-------+
1 row(s) fetched.
Elapsed 0.011 seconds.
> explain analyze select a, sum(b)
from t1
group by a;
+-------------------+---------------------------------------------------------------------------------------------------------------------------------------------------+
| plan_type | plan |
+-------------------+---------------------------------------------------------------------------------------------------------------------------------------------------+
| Plan with Metrics | AggregateExec: mode=FinalPartitioned, gby=[a@0 as a], aggr=[sum(t1.b)], metrics=[output_rows=2, elapsed_compute=4.67121ms, output_bytes=1088.0 B] |
| | CoalesceBatchesExec: target_batch_size=8192, metrics=[output_rows=2, elapsed_compute=17.875µs, output_bytes=192.0 KB] |
| | RepartitionExec: partitioning=Hash([a@0], 14), input_partitions=14, metrics=[] |
| | RepartitionExec: partitioning=RoundRobinBatch(14), input_partitions=1, metrics=[] |
| | AggregateExec: mode=Partial, gby=[a@0 as a], aggr=[sum(t1.b)], metrics=[output_rows=2, elapsed_compute=1.931542ms, output_bytes=544.0 B] |
| | DataSourceExec: partitions=1, partition_sizes=[1], metrics=[] |
| | |
+-------------------+---------------------------------------------------------------------------------------------------------------------------------------------------+
1 row(s) fetched.
Elapsed 0.018 seconds.
```
You can see for the bottom `AggregateExec` with `Partial` mode, it has 4 input rows, and after the pre-aggregation, the output size has been reduced to 2 rows, so a `reduction_factor` metric can be calculated as `2/4 => 50%`
### Describe the solution you'd like
Add `reduction_factor` metric for `AggregateExec` with `Partial` mode.
Reference PR: https://github.com/apache/datafusion/pull/18406
### Describe alternatives you've considered
_No response_
### Additional context
_No response_
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Re: [I] Support `reduction_fator` metric (for `EXPLAIN ANALYZE`) in `AggregateExec` [datafusion]
Posted by "petern48 (via GitHub)" <gi...@apache.org>.
petern48 commented on issue #18410:
URL: https://github.com/apache/datafusion/issues/18410#issuecomment-3478593734
take
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Re: [I] Support `reduction_fator` metric (for `EXPLAIN ANALYZE`) in `AggregateExec` [datafusion]
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb closed issue #18410: Support `reduction_fator` metric (for `EXPLAIN ANALYZE`) in `AggregateExec`
URL: https://github.com/apache/datafusion/issues/18410
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