[GitHub] [arrow-datafusion] Jefffrey commented on issue #5444: Expr.alias function not work with count aggregation

["Jefffrey (via GitHub)" <gi...@apache.org>]

Jefffrey commented on issue #5444:
URL: https://github.com/apache/arrow-datafusion/issues/5444#issuecomment-1452440185

   Yeah the reason is that `aggregate_statistics` physical optimizer rule sets the name of the output column like so:
   
   https://github.com/apache/arrow-datafusion/blob/f68214dc6553ede5f23ba54cac6150f4c1e18e8c/datafusion/core/src/physical_optimizer/aggregate_statistics.rs#L192-L196
   
   Ideally would take `casted_expr.name()` instead which would contain the alias you gave it. However what I've noticed is that it can contain the table as part of the name. So if it's switched to `casted_expr.name()` then following code:
   
   ```rust
   ctx
       .table("p")
       .await?
       .aggregate(vec![], vec![count(col("id"))])?
       .show().await?;
   ```
   
   Will output:
   
   ```
   +-------------+
   | COUNT(p.id) |
   +-------------+
   | 7300        |
   +-------------+
   ```
   
   Note the `p.id` instead of just `id`.
   
   P.S. this affects the other aggregate functions too, e.g.
   
   https://github.com/apache/arrow-datafusion/blob/f68214dc6553ede5f23ba54cac6150f4c1e18e8c/datafusion/core/src/physical_optimizer/aggregate_statistics.rs#L224


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