fix: when extracting metadata from expr, handle CastExpr

datafusion/physical-plan/src/projection.rs

@@ -40,7 +40,7 @@ use datafusion_common::stats::Precision;
 use datafusion_common::Result;
 use datafusion_execution::TaskContext;
 use datafusion_physical_expr::equivalence::ProjectionMapping;
-use datafusion_physical_expr::expressions::Literal;
+use datafusion_physical_expr::expressions::{CastExpr, Literal};
 
 use crate::execution_plan::CardinalityEffect;
 use futures::stream::{Stream, StreamExt};
@@ -246,6 +246,10 @@ pub(crate) fn get_field_metadata(
     e: &Arc<dyn PhysicalExpr>,
     input_schema: &Schema,
 ) -> Option<HashMap<String, String>> {
+    if let Some(cast) = e.as_any().downcast_ref::<CastExpr>() {
+        return get_field_metadata(cast.expr(), input_schema);
+    }
+
     // Look up field by index in schema (not NAME as there can be more than one
     // column with the same name)
     e.as_any()