FilterPushDown optimization through UNION ALL results in SchemaError

[jonmmease]

Describe the bug
There seems to be an interaction between the FilterPushDown logical optimization and the UNION ALL operator that results in a SchemaError.

Here is the simplest example I was able to identify:

To Reproduce

use std::sync::Arc;
use datafusion::arrow::datatypes::Schema;
use datafusion::datasource::empty::EmptyTable;
use datafusion::prelude::SessionContext;
use vegafusion_core::arrow::datatypes::{DataType, Field};

#[tokio::test]
async fn test_query() {
    let ctx = SessionContext::new();
    let schema = Schema::new(vec![
        Field::new("colA", DataType::Float64, true),
    ]);
    let table = EmptyTable::new(Arc::new(schema));
    ctx.register_table("tbl", Arc::new(table)).unwrap();

    let df = ctx.sql(r#"
WITH
    tbl_1 AS (SELECT "colA" AS "renamedA" FROM "tbl"),
    tbl_2 AS ((SELECT * FROM tbl_1) UNION ALL (SELECT * FROM tbl_1))
SELECT * FROM tbl_2 WHERE ("renamedA" IS NOT NULL)
    "#).await.unwrap();

    let result = df.collect().await.unwrap();
}

called `Result::unwrap()` on an `Err` value: SchemaError(FieldNotFound { qualifier: None, name: "renamedA", valid_fields: Some(["tbl.colA"]) })

Expected behavior
This code block should evaluate successfully to an empty record batch containing the renamedA column.

Additional context
The example executes successfully if UNION ALL is replaced by UNION. And it executes successfully if I comment out the use of the FilterPushDown in datafusion/core/src/execution/context.rs

[jonmmease]

Here is the optimized logical plan for the example above:

    Projection: #renamedA
      Union
        Projection: #tbl_1.renamedA
          Projection: #tbl.colA AS renamedA, alias=tbl_1
            Filter: #renamedA IS NOT NULL
              TableScan: tbl projection=[colA]
        Projection: #tbl_1.renamedA
          Projection: #tbl.colA AS renamedA, alias=tbl_1
            Filter: #renamedA IS NOT NULL
              TableScan: tbl projection=[colA],

It looks like the filter is pushed down too far (below the projection that creates the renamedA column).

[jonmmease]

Possibly related to #1509 and #1781

[jonmmease]

Fix proposed in #3282