support indexed fields proto

datafusion/physical-expr/src/expressions/get_indexed_field.rs

@@ -49,6 +49,11 @@ impl GetIndexedFieldExpr {
         Self { arg, key }
     }
 
+    /// Get the input key
+    pub fn key(&self) -> &ScalarValue {
+        &self.key
+    }
+
     /// Get the input expression
     pub fn arg(&self) -> &Arc<dyn PhysicalExpr> {
         &self.arg

datafusion/proto/proto/datafusion.proto

@@ -301,9 +301,16 @@ message LogicalExprNode {
 
     // Scalar UDF expressions
     ScalarUDFExprNode scalar_udf_expr = 20;
+
+    GetIndexedField get_indexed_field = 21;
   }
 }
 
+message GetIndexedField {
+  LogicalExprNode expr = 1;
+  ScalarValue key = 2;
+}
+
 message IsNull {
   LogicalExprNode expr = 1;
 }

datafusion/proto/src/from_proto.rs

@@ -928,6 +928,21 @@ pub fn parse_expr(
             op: from_proto_binary_op(&binary_expr.op)?,
             right: Box::new(parse_required_expr(&binary_expr.r, registry, "r")?),
         }),
+        ExprType::GetIndexedField(field) => {
+            let key = field.key.as_ref().ok_or_else(|| Error::required("value"))?;
+
+            let key = typechecked_scalar_value_conversion(
+                key.value.as_ref().ok_or_else(|| Error::required("value"))?,
+                protobuf::PrimitiveScalarType::Utf8,
+            )?;
+
+            let expr = parse_required_expr(&field.expr, registry, "expr")?;
+
+            Ok(Expr::GetIndexedField {
+                expr: Box::new(expr),
+                key,
+            })
+        }
         ExprType::Column(column) => Ok(Expr::Column(column.into())),
         ExprType::Literal(literal) => {
             let scalar_value: ScalarValue = literal.try_into()?;

datafusion/proto/src/to_proto.rs

@@ -710,8 +710,15 @@ impl TryFrom<&Expr> for protobuf::LogicalExprNode {
                 // see discussion in https://github.com/apache/arrow-datafusion/issues/2565
                 unimplemented!("subquery expressions are not supported yet")
             }
+            Expr::GetIndexedField { key, expr } => Self {
+                expr_type: Some(ExprType::GetIndexedField(Box::new(
+                    protobuf::GetIndexedField {
+                        key: Some(key.try_into()?),
+                        expr: Some(Box::new(expr.as_ref().try_into()?)),
+                    },
+                ))),
+            },
             Expr::QualifiedWildcard { .. }
-            | Expr::GetIndexedField { .. }
             | Expr::TryCast { .. }
             | Expr::GroupingSet(_) => unimplemented!(),
         };