feat: Add dynamic literals to ensure schema correctness

crates/polars-core/src/datatypes/_serde.rs

@@ -105,7 +105,7 @@ enum SerializableDataType {
     #[cfg(feature = "dtype-struct")]
     Struct(Vec<Field>),
     // some logical types we cannot know statically, e.g. Datetime
-    Unknown,
+    Unknown(UnknownKind),
     #[cfg(feature = "dtype-categorical")]
     Categorical(Option<Wrap<Utf8ViewArray>>, CategoricalOrdering),
     #[cfg(feature = "dtype-decimal")]
@@ -141,7 +141,7 @@ impl From<&DataType> for SerializableDataType {
             #[cfg(feature = "dtype-array")]
             Array(dt, width) => Self::Array(Box::new(dt.as_ref().into()), *width),
             Null => Self::Null,
-            Unknown => Self::Unknown,
+            Unknown(kind) => Self::Unknown(*kind),
             #[cfg(feature = "dtype-struct")]
             Struct(flds) => Self::Struct(flds.clone()),
             #[cfg(feature = "dtype-categorical")]
@@ -185,7 +185,7 @@ impl From<SerializableDataType> for DataType {
             #[cfg(feature = "dtype-array")]
             Array(dt, width) => Self::Array(Box::new((*dt).into()), width),
             Null => Self::Null,
-            Unknown => Self::Unknown,
+            Unknown(kind) => Self::Unknown(kind),
             #[cfg(feature = "dtype-struct")]
             Struct(flds) => Self::Struct(flds),
             #[cfg(feature = "dtype-categorical")]

crates/polars-core/src/datatypes/dtype.rs

@@ -9,7 +9,22 @@ pub type TimeZone = String;
 pub static DTYPE_ENUM_KEY: &str = "POLARS.CATEGORICAL_TYPE";
 pub static DTYPE_ENUM_VALUE: &str = "ENUM";
 
-#[derive(Clone, Debug, Default)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Default)]
+#[cfg_attr(
+    any(feature = "serde", feature = "serde-lazy"),
+    derive(Serialize, Deserialize)
+)]
+pub enum UnknownKind {
+    // Hold the value to determine the concrete size.
+    Int(i128),
+    Float,
+    // Can be Categorical or String
+    Str,
+    #[default]
+    Any,
+}
+
+#[derive(Clone, Debug)]
 pub enum DataType {
     Boolean,
     UInt8,
@@ -59,8 +74,13 @@ pub enum DataType {
     #[cfg(feature = "dtype-struct")]
     Struct(Vec<Field>),
     // some logical types we cannot know statically, e.g. Datetime
-    #[default]
-    Unknown,
+    Unknown(UnknownKind),
+}
+
+impl Default for DataType {
+    fn default() -> Self {
+        DataType::Unknown(UnknownKind::Any)
+    }
 }
 
 pub trait AsRefDataType {
@@ -144,7 +164,7 @@ impl DataType {
             DataType::List(inner) => inner.is_known(),
             #[cfg(feature = "dtype-struct")]
             DataType::Struct(fields) => fields.iter().all(|fld| fld.dtype.is_known()),
-            DataType::Unknown => false,
+            DataType::Unknown(_) => false,
             _ => true,
         }
     }
@@ -208,7 +228,14 @@ impl DataType {
 
     /// Check if this [`DataType`] is a basic numeric type (excludes Decimal).
     pub fn is_numeric(&self) -> bool {
-        self.is_float() || self.is_integer()
+        self.is_float() || self.is_integer() || self.is_dynamic()
+    }
+
+    pub fn is_dynamic(&self) -> bool {
+        matches!(
+            self,
+            DataType::Unknown(UnknownKind::Int(_) | UnknownKind::Float | UnknownKind::Str)
+        )
     }
 
     /// Check if this [`DataType`] is a boolean
@@ -382,6 +409,32 @@ impl DataType {
         }
     }
 
+    pub fn is_string(&self) -> bool {
+        matches!(self, DataType::String | DataType::Unknown(UnknownKind::Str))
+    }
+
+    pub fn is_categorical(&self) -> bool {
+        #[cfg(feature = "dtype-categorical")]
+        {
+            matches!(self, DataType::Categorical(_, _))
+        }
+        #[cfg(not(feature = "dtype-categorical"))]
+        {
+            false
+        }
+    }
+
+    pub fn is_enum(&self) -> bool {
+        #[cfg(feature = "dtype-categorical")]
+        {
+            matches!(self, DataType::Enum(_, _))
+        }
+        #[cfg(not(feature = "dtype-categorical"))]
+        {
+            false
+        }
+    }
+
     /// Convert to an Arrow Field
     pub fn to_arrow_field(&self, name: &str, pl_flavor: bool) -> ArrowField {
         let metadata = match self {
@@ -490,7 +543,7 @@ impl DataType {
                 Ok(ArrowDataType::Struct(fields))
             },
             BinaryOffset => Ok(ArrowDataType::LargeBinary),
-            Unknown => Ok(ArrowDataType::Unknown),
+            Unknown(_) => Ok(ArrowDataType::Unknown),
         }
     }
 
@@ -591,7 +644,12 @@ impl Display for DataType {
             DataType::Enum(_, _) => "enum",
             #[cfg(feature = "dtype-struct")]
             DataType::Struct(fields) => return write!(f, "struct[{}]", fields.len()),
-            DataType::Unknown => "unknown",
+            DataType::Unknown(kind) => match kind {
+                UnknownKind::Any => "unknown",
+                UnknownKind::Int(_) => "dyn int",
+                UnknownKind::Float => "dyn float",
+                UnknownKind::Str => "dyn str",
+            },
             DataType::BinaryOffset => "binary[offset]",
         };
         f.write_str(s)

crates/polars-core/src/datatypes/field.rs

@@ -114,6 +114,18 @@ impl Field {
     }
 }
 
+impl AsRef<DataType> for Field {
+    fn as_ref(&self) -> &DataType {
+        &self.dtype
+    }
+}
+
+impl AsRef<DataType> for DataType {
+    fn as_ref(&self) -> &DataType {
+        self
+    }
+}
+
 impl DataType {
     pub fn boxed(self) -> Box<DataType> {
         Box::new(self)

crates/polars-core/src/datatypes/mod.rs

@@ -115,8 +115,8 @@ macro_rules! impl_polars_num_datatype {
     };
 }
 
-macro_rules! impl_polars_datatype {
-    ($ca:ident, $variant:ident, $arr:ty, $lt:lifetime, $phys:ty, $zerophys:ty) => {
+macro_rules! impl_polars_datatype2 {
+    ($ca:ident, $dtype:expr, $arr:ty, $lt:lifetime, $phys:ty, $zerophys:ty) => {
         #[derive(Clone, Copy)]
         pub struct $ca {}
 
@@ -128,12 +128,18 @@ macro_rules! impl_polars_datatype {
 
             #[inline]
             fn get_dtype() -> DataType {
-                DataType::$variant
+                $dtype
             }
         }
     };
 }
 
+macro_rules! impl_polars_datatype {
+    ($ca:ident, $variant:ident, $arr:ty, $lt:lifetime, $phys:ty, $zerophys:ty) => {
+        impl_polars_datatype2!($ca, DataType::$variant, $arr, $lt, $phys, $zerophys);
+    };
+}
+
 impl_polars_num_datatype!(PolarsIntegerType, UInt8Type, UInt8, u8);
 impl_polars_num_datatype!(PolarsIntegerType, UInt16Type, UInt16, u16);
 impl_polars_num_datatype!(PolarsIntegerType, UInt32Type, UInt32, u32);
@@ -145,17 +151,18 @@ impl_polars_num_datatype!(PolarsIntegerType, Int64Type, Int64, i64);
 impl_polars_num_datatype!(PolarsFloatType, Float32Type, Float32, f32);
 impl_polars_num_datatype!(PolarsFloatType, Float64Type, Float64, f64);
 impl_polars_datatype!(DateType, Date, PrimitiveArray<i32>, 'a, i32, i32);
-#[cfg(feature = "dtype-decimal")]
-impl_polars_datatype!(DecimalType, Unknown, PrimitiveArray<i128>, 'a, i128, i128);
-impl_polars_datatype!(DatetimeType, Unknown, PrimitiveArray<i64>, 'a, i64, i64);
-impl_polars_datatype!(DurationType, Unknown, PrimitiveArray<i64>, 'a, i64, i64);
-impl_polars_datatype!(CategoricalType, Unknown, PrimitiveArray<u32>, 'a, u32, u32);
 impl_polars_datatype!(TimeType, Time, PrimitiveArray<i64>, 'a, i64, i64);
 impl_polars_datatype!(StringType, String, Utf8ViewArray, 'a, &'a str, Option<&'a str>);
 impl_polars_datatype!(BinaryType, Binary, BinaryViewArray, 'a, &'a [u8], Option<&'a [u8]>);
 impl_polars_datatype!(BinaryOffsetType, BinaryOffset, BinaryArray<i64>, 'a, &'a [u8], Option<&'a [u8]>);
 impl_polars_datatype!(BooleanType, Boolean, BooleanArray, 'a, bool, bool);
 
+#[cfg(feature = "dtype-decimal")]
+impl_polars_datatype2!(DecimalType, DataType::Unknown(UnknownKind::Any), PrimitiveArray<i128>, 'a, i128, i128);
+impl_polars_datatype2!(DatetimeType, DataType::Unknown(UnknownKind::Any), PrimitiveArray<i64>, 'a, i64, i64);
+impl_polars_datatype2!(DurationType, DataType::Unknown(UnknownKind::Any), PrimitiveArray<i64>, 'a, i64, i64);
+impl_polars_datatype2!(CategoricalType, DataType::Unknown(UnknownKind::Any), PrimitiveArray<u32>, 'a, u32, u32);
+
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct ListType {}
 unsafe impl PolarsDataType for ListType {

crates/polars-core/src/series/from.rs

@@ -123,7 +123,9 @@ impl Series {
                 }
             },
             Null => new_null(name, &chunks),
-            Unknown => panic!("uh oh, somehow we don't know the dtype?"),
+            Unknown(_) => {
+                panic!("dtype is unknown; consider supplying data-types for all operations")
+            },
             #[allow(unreachable_patterns)]
             _ => unreachable!(),
         }

crates/polars-core/src/utils/supertype.rs

@@ -1,3 +1,5 @@
+use num_traits::Signed;
+
 use super::*;
 
 /// Given two data types, determine the data type that both types can safely be cast to.
@@ -195,9 +197,9 @@ pub fn get_supertype(l: &DataType, r: &DataType) -> Option<DataType> {
             (Time, Float64) => Some(Float64),
 
             // every known type can be casted to a string except binary
-            (dt, String) if dt != &DataType::Unknown && dt != &DataType::Binary => Some(String),
+            (dt, String) if !matches!(dt, DataType::Unknown(UnknownKind::Any)) && dt != &DataType::Binary => Some(String),
 
-            (dt, String) if dt != &DataType::Unknown => Some(String),
+            (dt, String) if !matches!(dt, DataType::Unknown(UnknownKind::Any)) => Some(String),
 
             (dt, Null) => Some(dt.clone()),
 
@@ -253,7 +255,35 @@ pub fn get_supertype(l: &DataType, r: &DataType) -> Option<DataType> {
                 let st = get_supertype(inner_left, inner_right)?;
                 Some(DataType::List(Box::new(st)))
             }
-            (_, Unknown) => Some(Unknown),
+            #[cfg(feature = "dtype-struct")]
+            (Struct(inner), right @ Unknown(UnknownKind::Float | UnknownKind::Int(_))) => {
+                match inner.first() {
+                    Some(inner) => get_supertype(&inner.dtype, right),
+                    None => None
+                }
+            },
+            (dt, Unknown(kind)) => {
+                match kind {
+                    UnknownKind::Float | UnknownKind::Int(_) if dt.is_float() | dt.is_string() => Some(dt.clone()),
+                    UnknownKind::Float if dt.is_numeric() => Some(Unknown(UnknownKind::Float)),
+                    UnknownKind::Str if dt.is_string() | dt.is_enum() => Some(dt.clone()),
+                    #[cfg(feature = "dtype-categorical")]
+                    UnknownKind::Str if dt.is_categorical()  => {
+                        let Categorical(_, ord) = dt else { unreachable!()};
+                        Some(Categorical(None, *ord))
+                    },
+                    dynam if dt.is_null() => Some(Unknown(*dynam)),
+                    UnknownKind::Int(v) if dt.is_numeric() => {
+                        let smallest_fitting_dtype = if dt.is_unsigned_integer() && v.is_positive() {
+                            materialize_dyn_int_pos(*v).dtype()
+                        } else {
+                            materialize_smallest_dyn_int(*v).dtype()
+                        };
+                        get_supertype(dt, &smallest_fitting_dtype)
+                    }
+                    _ => Some(Unknown(UnknownKind::Any))
+                }
+            },
             #[cfg(feature = "dtype-struct")]
             (Struct(fields_a), Struct(fields_b)) => {
                 super_type_structs(fields_a, fields_b)
@@ -341,3 +371,54 @@ fn super_type_structs(fields_a: &[Field], fields_b: &[Field]) -> Option<DataType
         Some(DataType::Struct(new_fields))
     }
 }
+
+pub fn materialize_dyn_int(v: i128) -> AnyValue<'static> {
+    // Try to get the "smallest" fitting value.
+    // TODO! next breaking go to true smallest.
+    match i32::try_from(v).ok() {
+        Some(v) => AnyValue::Int32(v),
+        None => match i64::try_from(v).ok() {
+            Some(v) => AnyValue::Int64(v),
+            None => match u64::try_from(v).ok() {
+                Some(v) => AnyValue::UInt64(v),
+                None => AnyValue::Null,
+            },
+        },
+    }
+}
+fn materialize_dyn_int_pos(v: i128) -> AnyValue<'static> {
+    // Try to get the "smallest" fitting value.
+    // TODO! next breaking go to true smallest.
+    match u8::try_from(v).ok() {
+        Some(v) => AnyValue::UInt8(v),
+        None => match u16::try_from(v).ok() {
+            Some(v) => AnyValue::UInt16(v),
+            None => match u32::try_from(v).ok() {
+                Some(v) => AnyValue::UInt32(v),
+                None => match u64::try_from(v).ok() {
+                    Some(v) => AnyValue::UInt64(v),
+                    None => AnyValue::Null,
+                },
+            },
+        },
+    }
+}
+
+fn materialize_smallest_dyn_int(v: i128) -> AnyValue<'static> {
+    match i8::try_from(v).ok() {
+        Some(v) => AnyValue::Int8(v),
+        None => match i16::try_from(v).ok() {
+            Some(v) => AnyValue::Int16(v),
+            None => match i32::try_from(v).ok() {
+                Some(v) => AnyValue::Int32(v),
+                None => match i64::try_from(v).ok() {
+                    Some(v) => AnyValue::Int64(v),
+                    None => match u64::try_from(v).ok() {
+                        Some(v) => AnyValue::UInt64(v),
+                        None => AnyValue::Null,
+                    },
+                },
+            },
+        },
+    }
+}

crates/polars-lazy/src/physical_plan/expressions/literal.rs

@@ -93,6 +93,12 @@ impl PhysicalExpr for LiteralExpr {
                 .into_time()
                 .into_series(),
             Series(series) => series.deref().clone(),
+            lv @ (Int(_) | Float(_) | StrCat(_)) => polars_core::prelude::Series::from_any_values(
+                LITERAL_NAME,
+                &[lv.to_any_value().unwrap()],
+                false,
+            )
+            .unwrap(),
         };
         Ok(s)
     }

crates/polars-lazy/src/physical_plan/streaming/convert_alp.rs

@@ -407,7 +407,7 @@ pub(crate) fn insert_streaming_nodes(
                             .iter()
                             .all(|fld| allowed_dtype(fld.data_type(), string_cache)),
                         // We need to be able to sink to disk or produce the aggregate return dtype.
-                        DataType::Unknown => false,
+                        DataType::Unknown(_) => false,
                         #[cfg(feature = "dtype-decimal")]
                         DataType::Decimal(_, _) => false,
                         _ => true,

crates/polars-lazy/src/tests/optimization_checks.rs

@@ -295,12 +295,12 @@ pub fn test_predicate_block_cast() -> PolarsResult<()> {
     let lf1 = df
         .clone()
         .lazy()
-        .with_column(col("value").cast(DataType::Int16) * lit(0.1f32))
+        .with_column(col("value").cast(DataType::Int16) * lit(0.1).cast(DataType::Float32))
         .filter(col("value").lt(lit(2.5f32)));
 
     let lf2 = df
         .lazy()
-        .select([col("value").cast(DataType::Int16) * lit(0.1f32)])
+        .select([col("value").cast(DataType::Int16) * lit(0.1).cast(DataType::Float32)])
         .filter(col("value").lt(lit(2.5f32)));
 
     for lf in [lf1, lf2] {

crates/polars-lazy/src/tests/queries.rs

@@ -550,7 +550,7 @@ fn test_simplify_expr() {
 
     let plan = df
         .lazy()
-        .select(&[lit(1.0f32) + lit(1.0f32) + col("sepal_width")])
+        .select(&[lit(1.0) + lit(1.0) + col("sepal_width")])
         .logical_plan;
 
     let mut expr_arena = Arena::new();
@@ -564,7 +564,7 @@ fn test_simplify_expr() {
         .unwrap();
     let plan = node_to_lp(lp_top, &expr_arena, &mut lp_arena);
     assert!(
-        matches!(plan, DslPlan::Select{ expr, ..} if matches!(&expr[0], Expr::BinaryExpr{left, ..} if **left == Expr::Literal(LiteralValue::Float32(2.0))))
+        matches!(plan, DslPlan::Select{ expr, ..} if matches!(&expr[0], Expr::BinaryExpr{left, ..} if **left == Expr::Literal(LiteralValue::Float(2.0))))
     );
 }