pepijnve opened a new issue, #19684:
URL: https://github.com/apache/datafusion/issues/19684
### Describe the bug
When the common subexpression elimination deduplicates aggregations it can
generate aliases for the common expression of the form `__common_expr_<n>`. In
the logical plan explain output this gets output as `<original expr> as
__common_expr_<n>`. In the physical plan explain output though only
`__common_expr_<n>` is printed. The actual expression corresponding to this
alias is no longer visible. This makes the explain output hard to interpret.
### To Reproduce
Here's an example logic plan constructed using the data frame API. The
problematic line is
```
AggregateExec: mode=Partial, gby=[idx@1 as idx], aggr=[__common_expr_1]
```
```
Logical plan
============
Projection: idx, agg, ord
Aggregate: groupBy=[[idx]], aggr=[[sum(column1) AS agg, sum(column1) AS
ord]]
Projection: column1, column2, CASE WHEN column2 <= Int64(0) THEN
Int64(0) WHEN column2 <= Int64(200) THEN Int64(1) WHEN column2 <= Int64(314)
THEN Int64(3) ELSE Int64(4) END AS idx
Values: (Int64(1), Int64(100)), (Int64(2), Int64(200)), (Int64(3),
Int64(314))
Optimized logical plan
======================
Projection: idx, __common_expr_1 AS agg, __common_expr_1 AS ord
Aggregate: groupBy=[[idx]], aggr=[[sum(column1) AS __common_expr_1]]
Projection: column1, CASE WHEN column2 <= Int64(0) THEN Int64(0) WHEN
column2 <= Int64(200) THEN Int64(1) WHEN column2 <= Int64(314) THEN Int64(3)
ELSE Int64(4) END AS idx
Values: (Int64(1), Int64(100)), (Int64(2), Int64(200)), (Int64(3),
Int64(314))
Physical plan
=============
ProjectionExec: expr=[idx@0 as idx, __common_expr_1@1 as agg,
__common_expr_1@1 as ord]
AggregateExec: mode=FinalPartitioned, gby=[idx@0 as idx],
aggr=[__common_expr_1]
RepartitionExec: partitioning=Hash([idx@0], 10), input_partitions=1
AggregateExec: mode=Partial, gby=[idx@1 as idx], aggr=[__common_expr_1]
ProjectionExec: expr=[column1@0 as column1, CASE WHEN column2@1 <= 0
THEN 0 WHEN column2@1 <= 200 THEN 1 WHEN column2@1 <= 314 THEN 3 ELSE 4 END as
idx]
DataSourceExec: partitions=1, partition_sizes=[1]
```
### Expected behavior
Rather than
```
AggregateExec: mode=Partial, gby=[idx@1 as idx], aggr=[__common_expr_1]
```
the explain output should show
```
AggregateExec: mode=Partial, gby=[idx@1 as idx], aggr=[sum(column1@0) as
__common_expr_1]
```
similarly to how the group by expression are printed.
### Additional context
_No response_
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