SimplifyExpressions errors when simplifying `power` fn

[wolffcm]

Describe the bug

When calling the power function with a constant in the second argument, I get an error:

Internal error: Optimizer rule 'simplify_expressions' failed due to unexpected error: Internal error: The expr has more than one schema, could not determine data type. This was likely caused by a bug in DataFusion's code and we would welcome that you file an bug report in our issue tracker.

To Reproduce

with datafusion-cli:

select power(f, 100) from (values(10.0)) as t(f);

I was also able to reproduce this with a unit test in datafusion/optimizer/src/simplify_expressions/simlify_exprs.rs:

    #[test]
    fn simplify_power() -> Result<()> {
        let schema = Schema::new(vec![
            Field::new("f", DataType::Float64, false),
        ]);
        let table_scan = table_scan(Some("test"), &schema, None)
            .expect("creating scan")
            .build()
            .expect("building plan");

        let plan = LogicalPlanBuilder::from(table_scan)
            .project(vec![call_fn("power", vec![col("f"), lit(1)])?])?
            .build()?;
        let rule = SimplifyExpressions::new();
        let _optimized_plan = rule
            .try_optimize(&plan, &OptimizerContext::new())
            .unwrap()
            .expect("failed to optimize plan");
        Ok(())
    }

Expected behavior

Calling power with a constant is a reasonable thing to want to do, so I would expect this to work.

Additional context

Unless the optimizer is configured with skip_failed_rules set to false, this could manifest in other, or the query might succeed just fine.

Related issue: #4685

I found this specifically when invoking power but this same issue probably occurs when simplifying other expressions.

In IOx we want to run with skip_failed_rules set to false specifically so we can return reasonable error messages to the user: https://github.com/influxdata/influxdb_iox/issues/7330

This test failure seems to happen in simpl_pow when trying to get the data type of the exponent argument:
https://github.com/apache/arrow-datafusion/blob/fcd8b899e2a62f798413c536f47078289ece9d05/datafusion/optimizer/src/simplify_expressions/utils.rs#L403
And then the SimplifyContext can't get the type because there is "more than one schema":
https://github.com/apache/arrow-datafusion/blob/fcd8b899e2a62f798413c536f47078289ece9d05/datafusion/optimizer/src/simplify_expressions/context.rs#L135

[alamb]

I am not sure why this is happening -- I think some debugging is in order.

Maybe one way to start is to figure out what the two schema are:

https://github.com/apache/arrow-datafusion/blob/03851ce6892c4a682058bbc8689dd7d6d7990ad0/datafusion/optimizer/src/simplify_expressions/context.rs#L130-L138

[wolffcm]

I am looking into this

[wolffcm]

For the simple example in the unit test, the plan is:

Projection: power(test.f, Int32(1))
  TableScan: test

And the two schemas in the error message are:

[
    DFSchema { fields: [
        DFField { qualifier: None, field: Field { name: "power(test.f,Int32(1))", data_type: Float64, nullable: true, dict_id: 0, dict_is_ordered: false, metadata: {} } }
    ], metadata: {} }, 
    DFSchema { fields: [
        DFField { qualifier: Some(Bare { table: "test" }), field: Field { name: "f", data_type: Float64, nullable: false, dict_id: 0, dict_is_ordered: false, metadata: {} } }
    ], metadata: {} }
]

The first one is from the Project and the other is from the Scan.

After spending some time looking at this today I think I might have a potential fix, will draft a PR tomorrow.

[alamb]

I believe the upstream fix is now available in IOx after https://github.com/influxdata/influxdb_iox/pull/7630