use logical type for signature

Signed-off-by: jayzhan211 <jayzhan211@gmail.com>

datafusion/common/src/types/logical.rs

@@ -98,6 +98,12 @@ impl fmt::Debug for dyn LogicalType {
     }
 }
 
+impl std::fmt::Display for dyn LogicalType {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{self:?}")
+    }
+}
+
 impl PartialEq for dyn LogicalType {
     fn eq(&self, other: &Self) -> bool {
         self.signature().eq(&other.signature())

datafusion/common/src/types/native.rs

@@ -16,15 +16,16 @@
 // under the License.
 
 use super::{
-    LogicalField, LogicalFieldRef, LogicalFields, LogicalType, LogicalUnionFields,
-    TypeSignature,
+    LogicalField, LogicalFieldRef, LogicalFields, LogicalType, LogicalTypeRef,
+    LogicalUnionFields, TypeSignature,
 };
 use crate::error::{Result, _internal_err};
 use arrow::compute::can_cast_types;
 use arrow_schema::{
     DataType, Field, FieldRef, Fields, IntervalUnit, TimeUnit, UnionFields,
 };
 use std::sync::Arc;
+use std::sync::{Arc, OnceLock};
 
 /// Representation of a type that DataFusion can handle natively. It is a subset
 /// of the physical variants in Arrow's native [`DataType`].
@@ -348,6 +349,12 @@ impl LogicalType for NativeType {
 // mapping solutions to provide backwards compatibility while transitioning from
 // the purely physical system to a logical / physical system.
 
+impl From<&DataType> for NativeType {
+    fn from(value: &DataType) -> Self {
+        value.clone().into()
+    }
+}
+
 impl From<DataType> for NativeType {
     fn from(value: DataType) -> Self {
         use NativeType::*;
@@ -392,8 +399,37 @@ impl From<DataType> for NativeType {
     }
 }
 
-impl From<&DataType> for NativeType {
-    fn from(value: &DataType) -> Self {
-        value.clone().into()
+impl NativeType {
+    #[inline]
+    pub fn is_numeric(&self) -> bool {
+        use NativeType::*;
+        matches!(
+            self,
+            UInt8
+                | UInt16
+                | UInt32
+                | UInt64
+                | Int8
+                | Int16
+                | Int32
+                | Int64
+                | Float16
+                | Float32
+                | Float64
+        )
+    }
+
+    /// This function is the NativeType version of `can_cast_types`.
+    /// It handles general coercion rules that are widely applicable.
+    /// Avoid adding specific coercion cases here.
+    /// Aim to keep this logic as SIMPLE as possible!
+    pub fn can_cast_to(&self, target_type: &Self) -> bool {
+        // In Postgres, most functions coerce numeric strings to numeric inputs,
+        // but they do not accept numeric inputs as strings.
+        if self.is_numeric() && target_type == &NativeType::String {
+            return false;
+        }
+
+        true
     }
 }

datafusion/expr-common/src/signature.rs

@@ -19,6 +19,7 @@
 //! and return types of functions in DataFusion.
 
 use arrow::datatypes::DataType;
+use datafusion_common::types::LogicalTypeRef;
 
 /// Constant that is used as a placeholder for any valid timezone.
 /// This is used where a function can accept a timestamp type with any
@@ -109,7 +110,7 @@ pub enum TypeSignature {
     /// For example, `Coercible(vec![DataType::Float64])` accepts
     /// arguments like `vec![DataType::Int32]` or `vec![DataType::Float32]`
     /// since i32 and f32 can be casted to f64
-    Coercible(Vec<DataType>),
+    Coercible(Vec<LogicalTypeRef>),
     /// Fixed number of arguments of arbitrary types
     /// If a function takes 0 argument, its `TypeSignature` should be `Any(0)`
     Any(usize),
@@ -201,7 +202,10 @@ impl TypeSignature {
             TypeSignature::Numeric(num) => {
                 vec![format!("Numeric({num})")]
             }
-            TypeSignature::Exact(types) | TypeSignature::Coercible(types) => {
+            TypeSignature::Coercible(types) => {
+                vec![Self::join_types(types, ", ")]
+            }
+            TypeSignature::Exact(types) => {
                 vec![Self::join_types(types, ", ")]
             }
             TypeSignature::Any(arg_count) => {
@@ -322,7 +326,7 @@ impl Signature {
         }
     }
     /// Target coerce types in order
-    pub fn coercible(target_types: Vec<DataType>, volatility: Volatility) -> Self {
+    pub fn coercible(target_types: Vec<LogicalTypeRef>, volatility: Volatility) -> Self {
         Self {
             type_signature: TypeSignature::Coercible(target_types),
             volatility,

datafusion/expr/src/type_coercion/functions.rs

@@ -23,6 +23,7 @@ use arrow::{
 };
 use datafusion_common::{
     exec_err, internal_datafusion_err, internal_err, plan_err,
+    types::{logical_string, NativeType},
     utils::{coerced_fixed_size_list_to_list, list_ndims},
     Result,
 };
@@ -401,6 +402,10 @@ fn get_valid_types(
             .map(|valid_type| current_types.iter().map(|_| valid_type.clone()).collect())
             .collect(),
         TypeSignature::String(number) => {
+            // TODO: we can switch to coercible after all the string functions support utf8view since it is choosen as the default string type.
+            //
+            // let data_types = get_valid_types(&TypeSignature::Coercible(vec![logical_string(); *number]), current_types)?.swap_remove(0);
+
             if *number < 1 {
                 return plan_err!(
                     "The signature expected at least one argument but received {}",
@@ -415,20 +420,38 @@ fn get_valid_types(
                 );
             }
 
-            fn coercion_rule(
+            let mut new_types = Vec::with_capacity(current_types.len());
+            for data_type in current_types.iter() {
+                let logical_data_type: NativeType = data_type.into();
+
+                match logical_data_type {
+                    NativeType::String => {
+                        new_types.push(data_type.to_owned());
+                    }
+                    NativeType::Null => {
+                        new_types.push(DataType::Utf8);
+                    }
+                    _ => {
+                        return plan_err!(
+                            "The signature expected NativeType::String but received {data_type}"
+                        );
+                    }
+                }
+            }
+
+            let data_types = new_types;
+
+            // Find the common string type for the given types
+            fn find_common_type(
                 lhs_type: &DataType,
                 rhs_type: &DataType,
             ) -> Result<DataType> {
                 match (lhs_type, rhs_type) {
-                    (DataType::Null, DataType::Null) => Ok(DataType::Utf8),
-                    (DataType::Null, data_type) | (data_type, DataType::Null) => {
-                        coercion_rule(data_type, &DataType::Utf8)
-                    }
                     (DataType::Dictionary(_, lhs), DataType::Dictionary(_, rhs)) => {
-                        coercion_rule(lhs, rhs)
+                        find_common_type(lhs, rhs)
                     }
                     (DataType::Dictionary(_, v), other)
-                    | (other, DataType::Dictionary(_, v)) => coercion_rule(v, other),
+                    | (other, DataType::Dictionary(_, v)) => find_common_type(v, other),
                     _ => {
                         if let Some(coerced_type) = string_coercion(lhs_type, rhs_type) {
                             Ok(coerced_type)
@@ -444,15 +467,13 @@ fn get_valid_types(
             }
 
             // Length checked above, safe to unwrap
-            let mut coerced_type = current_types.first().unwrap().to_owned();
-            for t in current_types.iter().skip(1) {
-                coerced_type = coercion_rule(&coerced_type, t)?;
+            let mut coerced_type = data_types.first().unwrap().to_owned();
+            for t in data_types.iter().skip(1) {
+                coerced_type = find_common_type(&coerced_type, t)?;
             }
 
             fn base_type_or_default_type(data_type: &DataType) -> DataType {
-                if data_type.is_null() {
-                    DataType::Utf8
-                } else if let DataType::Dictionary(_, v) = data_type {
+                if let DataType::Dictionary(_, v) = data_type {
                     base_type_or_default_type(v)
                 } else {
                     data_type.to_owned()
@@ -506,14 +527,25 @@ fn get_valid_types(
                 );
             }
 
+            let mut new_types = Vec::with_capacity(current_types.len());
             for (data_type, target_type) in current_types.iter().zip(target_types.iter())
             {
-                if !can_cast_types(data_type, target_type) {
-                    return plan_err!("{data_type} is not coercible to {target_type}");
+                let logical_data_type: NativeType = data_type.into();
+                if logical_data_type == *target_type.native() {
+                    new_types.push(data_type.to_owned());
+                } else if logical_data_type.can_cast_to(target_type.native()) {
+                    let casted_type = target_type.default_cast_for(data_type)?;
+                    new_types.push(casted_type);
+                } else {
+                    return plan_err!(
+                        "The signature expected {:?} but received {:?}",
+                        target_type.native(),
+                        logical_data_type
+                    );
                 }
             }
 
-            vec![target_types.to_owned()]
+            vec![new_types]
         }
         TypeSignature::Uniform(number, valid_types) => valid_types
             .iter()

datafusion/functions-aggregate/src/stddev.rs

@@ -25,6 +25,7 @@ use std::sync::{Arc, OnceLock};
 use arrow::array::Float64Array;
 use arrow::{array::ArrayRef, datatypes::DataType, datatypes::Field};
 
+use datafusion_common::types::logical_float64;
 use datafusion_common::{internal_err, not_impl_err, Result};
 use datafusion_common::{plan_err, ScalarValue};
 use datafusion_expr::aggregate_doc_sections::DOC_SECTION_STATISTICAL;
@@ -72,7 +73,7 @@ impl Stddev {
     pub fn new() -> Self {
         Self {
             signature: Signature::coercible(
-                vec![DataType::Float64],
+                vec![logical_float64()],
                 Volatility::Immutable,
             ),
             alias: vec!["stddev_samp".to_string()],

datafusion/functions-aggregate/src/variance.rs

@@ -29,7 +29,8 @@ use std::sync::OnceLock;
 use std::{fmt::Debug, sync::Arc};
 
 use datafusion_common::{
-    downcast_value, not_impl_err, plan_err, DataFusionError, Result, ScalarValue,
+    downcast_value, not_impl_err, plan_err, types::logical_float64, DataFusionError,
+    Result, ScalarValue,
 };
 use datafusion_expr::aggregate_doc_sections::DOC_SECTION_GENERAL;
 use datafusion_expr::{
@@ -83,7 +84,7 @@ impl VarianceSample {
         Self {
             aliases: vec![String::from("var_sample"), String::from("var_samp")],
             signature: Signature::coercible(
-                vec![DataType::Float64],
+                vec![logical_float64()],
                 Volatility::Immutable,
             ),
         }

datafusion/functions/src/string/bit_length.rs

@@ -79,7 +79,7 @@ impl ScalarUDFImpl for BitLengthFunc {
                 ScalarValue::LargeUtf8(v) => Ok(ColumnarValue::Scalar(
                     ScalarValue::Int64(v.as_ref().map(|x| (x.len() * 8) as i64)),
                 )),
-                _ => unreachable!(),
+                _ => unreachable!("bit length"),
             },
         }
     }

datafusion/functions/src/string/concat.rs

@@ -186,7 +186,7 @@ impl ScalarUDFImpl for ConcatFunc {
                         }
                     };
                 }
-                _ => unreachable!(),
+                _ => unreachable!("concat"),
             }
         }
 

datafusion/functions/src/string/concat_ws.rs

@@ -164,7 +164,7 @@ impl ScalarUDFImpl for ConcatWsFunc {
                     ColumnarValueRef::NonNullableArray(string_array)
                 }
             }
-            _ => unreachable!(),
+            _ => unreachable!("concat ws"),
         };
 
         let mut columns = Vec::with_capacity(args.len() - 1);

datafusion/functions/src/string/lower.rs

@@ -107,7 +107,7 @@ mod tests {
         let args = vec![ColumnarValue::Array(input)];
         let result = match func.invoke(&args)? {
             ColumnarValue::Array(result) => result,
-            _ => unreachable!(),
+            _ => unreachable!("lower"),
         };
         assert_eq!(&expected, &result);
         Ok(())

datafusion/functions/src/string/octet_length.rs

@@ -82,7 +82,7 @@ impl ScalarUDFImpl for OctetLengthFunc {
                 ScalarValue::Utf8View(v) => Ok(ColumnarValue::Scalar(
                     ScalarValue::Int32(v.as_ref().map(|x| x.len() as i32)),
                 )),
-                _ => unreachable!(),
+                _ => unreachable!("OctetLengthFunc"),
             },
         }
     }

datafusion/functions/src/string/upper.rs

@@ -107,7 +107,7 @@ mod tests {
         let args = vec![ColumnarValue::Array(input)];
         let result = match func.invoke(&args)? {
             ColumnarValue::Array(result) => result,
-            _ => unreachable!(),
+            _ => unreachable!("upper"),
         };
         assert_eq!(&expected, &result);
         Ok(())

datafusion/functions/src/unicode/character_length.rs

@@ -128,7 +128,7 @@ fn character_length(args: &[ArrayRef]) -> Result<ArrayRef> {
             let string_array = args[0].as_string_view();
             character_length_general::<Int32Type, _>(string_array)
         }
-        _ => unreachable!(),
+        _ => unreachable!("CharacterLengthFunc"),
     }
 }
 

datafusion/functions/src/unicode/lpad.rs

@@ -162,7 +162,7 @@ pub fn lpad<T: OffsetSizeTrait>(args: &[ArrayRef]) -> Result<ArrayRef> {
             length_array,
             &args[2],
         ),
-        (_, _) => unreachable!(),
+        (_, _) => unreachable!("lpad"),
     }
 }
 

datafusion/sqllogictest/test_files/scalar.slt

@@ -1940,7 +1940,7 @@ select position('' in '')
 ----
 1
 
-query error DataFusion error: Error during planning: Error during planning: Int64 and Int64 are not coercible to a common string
+query error DataFusion error: Error during planning: Error during planning: The signature expected NativeType::String but received Int64
 select position(1 in 1)
 
 query I