fix bug with to_timestamp and InitCap logical serialization, add …

…roundtrip test between expression and proto, (#8868)

* add roundtrip test between expression and proto
---------

Co-authored-by: Andrew Lamb <andrew@nerdnetworks.org>

datafusion/proto/Cargo.toml

@@ -54,4 +54,5 @@ serde_json = { workspace = true, optional = true }
 
 [dev-dependencies]
 doc-comment = { workspace = true }
+strum = { version = "0.25.0", features = ["derive"] }
 tokio = "1.18"

datafusion/proto/src/logical_plan/from_proto.rs

@@ -58,8 +58,8 @@ use datafusion_expr::{
     current_date, current_time, date_bin, date_part, date_trunc, decode, degrees, digest,
     encode, exp,
     expr::{self, InList, Sort, WindowFunction},
-    factorial, find_in_set, flatten, floor, from_unixtime, gcd, gen_range, isnan, iszero,
-    lcm, left, levenshtein, ln, log, log10, log2,
+    factorial, find_in_set, flatten, floor, from_unixtime, gcd, gen_range, initcap,
+    isnan, iszero, lcm, left, levenshtein, ln, log, log10, log2,
     logical_plan::{PlanType, StringifiedPlan},
     lower, lpad, ltrim, md5, nanvl, now, nullif, octet_length, overlay, pi, power,
     radians, random, regexp_match, regexp_replace, repeat, replace, reverse, right,
@@ -1585,7 +1585,7 @@ pub fn parse_expr(
                     Ok(character_length(parse_expr(&args[0], registry)?))
                 }
                 ScalarFunction::Chr => Ok(chr(parse_expr(&args[0], registry)?)),
-                ScalarFunction::InitCap => Ok(ascii(parse_expr(&args[0], registry)?)),
+                ScalarFunction::InitCap => Ok(initcap(parse_expr(&args[0], registry)?)),
                 ScalarFunction::Gcd => Ok(gcd(
                     parse_expr(&args[0], registry)?,
                     parse_expr(&args[1], registry)?,
@@ -1742,7 +1742,16 @@ pub fn parse_expr(
                     Ok(arrow_typeof(parse_expr(&args[0], registry)?))
                 }
                 ScalarFunction::ToTimestamp => {
-                    Ok(to_timestamp_seconds(parse_expr(&args[0], registry)?))
+                    let args: Vec<_> = args
+                        .iter()
+                        .map(|expr| parse_expr(expr, registry))
+                        .collect::<Result<_, _>>()?;
+                    Ok(Expr::ScalarFunction(
+                        datafusion_expr::expr::ScalarFunction::new(
+                            BuiltinScalarFunction::ToTimestamp,
+                            args,
+                        ),
+                    ))
                 }
                 ScalarFunction::Flatten => Ok(flatten(parse_expr(&args[0], registry)?)),
                 ScalarFunction::StringToArray => Ok(string_to_array(

datafusion/proto/tests/cases/serialize.rs

@@ -243,3 +243,40 @@ fn context_with_udf() -> SessionContext {
 
     ctx
 }
+
+#[test]
+fn test_expression_serialization_roundtrip() {
+    use datafusion_common::ScalarValue;
+    use datafusion_expr::expr::ScalarFunction;
+    use datafusion_expr::BuiltinScalarFunction;
+    use datafusion_proto::logical_plan::from_proto::parse_expr;
+    use datafusion_proto::protobuf::LogicalExprNode;
+    use strum::IntoEnumIterator;
+
+    let ctx = SessionContext::new();
+    let lit = Expr::Literal(ScalarValue::Utf8(None));
+    for builtin_fun in BuiltinScalarFunction::iter() {
+        // default to 4 args (though some exprs like substr have error checking)
+        let num_args = match builtin_fun {
+            BuiltinScalarFunction::Substr => 3,
+            _ => 4,
+        };
+        let args: Vec<_> = std::iter::repeat(&lit).take(num_args).cloned().collect();
+        let expr = Expr::ScalarFunction(ScalarFunction::new(builtin_fun, args));
+
+        let proto = LogicalExprNode::try_from(&expr).unwrap();
+        let deserialize = parse_expr(&proto, &ctx).unwrap();
+
+        let serialize_name = extract_function_name(&expr);
+        let deserialize_name = extract_function_name(&deserialize);
+
+        assert_eq!(serialize_name, deserialize_name);
+    }
+
+    /// Extracts the first part of a function name
+    /// 'foo(bar)' -> 'foo'
+    fn extract_function_name(expr: &Expr) -> String {
+        let name = expr.display_name().unwrap();
+        name.split('(').next().unwrap().to_string()
+    }
+}