Regression: projection pushdown doesn't work as expected in DF50

[xudong963]

• Related to Release DataFusion 50.0.0 (Aug/Sep 2025) #16799

// t1 contains a,b
DF49
> explain select from t1 where t1.a > 1;
+--------------+----------------------------------+
| plan_type    | plan                             |
+--------------+----------------------------------+
| logical_plan | Projection:                      |
|              |   Filter: t1.a > Int32(1)        |
|              |     TableScan: t1 projection=[a] |
+--------------+----------------------------------+
1 row(s) fetched.
Elapsed 0.004 seconds.

DF50
> explain select from t1 where t1.a > 1;
+--------------+-----------------------------------+
| plan_type    | plan                              |
+--------------+-----------------------------------+
| logical_plan | Filter: t1.a > Int32(1)           |
|              |   TableScan: t1 projection=[a, b] |
+--------------+-----------------------------------+
1 row(s) fetched.
Elapsed 0.003 seconds.

[adriangb]

I ran a bisect and found that #17295 introduced this bug