Various refactors to string functions (#19402)

## Which issue does this PR close?

N/A

## Rationale for this change

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in the issue then this section is not needed.
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your changes and offer better suggestions for fixes.
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Clean up some signatures & unnecessary code in string functions

## What changes are included in this PR?

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is sometimes worth providing a summary of the individual changes in this
PR.
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Various refactors, see comments.

## Are these changes tested?

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Existing tests.

## Are there any user-facing changes?

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No.

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Author: Jefffrey

datafusion/functions/src/string/ends_with.rs

@@ -23,6 +23,7 @@ use arrow::compute::kernels::comparison::ends_with as arrow_ends_with;
 use arrow::datatypes::DataType;
 
 use datafusion_common::types::logical_string;
+use datafusion_common::utils::take_function_args;
 use datafusion_common::{Result, ScalarValue, exec_err};
 use datafusion_expr::binary::{binary_to_string_coercion, string_coercion};
 use datafusion_expr::{
@@ -95,12 +96,7 @@ impl ScalarUDFImpl for EndsWithFunc {
     }
 
     fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
-        let [str_arg, suffix_arg] = args.args.as_slice() else {
-            return exec_err!(
-                "ends_with was called with {} arguments, expected 2",
-                args.args.len()
-            );
-        };
+        let [str_arg, suffix_arg] = take_function_args(self.name(), &args.args)?;
 
         // Determine the common type for coercion
         let coercion_type = string_coercion(

datafusion/functions/src/string/ltrim.rs

@@ -21,7 +21,7 @@ use std::any::Any;
 use std::sync::Arc;
 
 use crate::string::common::*;
-use crate::utils::{make_scalar_function, utf8_to_str_type};
+use crate::utils::make_scalar_function;
 use datafusion_common::types::logical_string;
 use datafusion_common::{Result, exec_err};
 use datafusion_expr::function::Hint;
@@ -115,11 +115,7 @@ impl ScalarUDFImpl for LtrimFunc {
     }
 
     fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
-        if arg_types[0] == DataType::Utf8View {
-            Ok(DataType::Utf8View)
-        } else {
-            utf8_to_str_type(&arg_types[0], "ltrim")
-        }
+        Ok(arg_types[0].clone())
     }
 
     fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {

datafusion/functions/src/string/rtrim.rs

@@ -21,7 +21,7 @@ use std::any::Any;
 use std::sync::Arc;
 
 use crate::string::common::*;
-use crate::utils::{make_scalar_function, utf8_to_str_type};
+use crate::utils::make_scalar_function;
 use datafusion_common::types::logical_string;
 use datafusion_common::{Result, exec_err};
 use datafusion_expr::function::Hint;
@@ -115,11 +115,7 @@ impl ScalarUDFImpl for RtrimFunc {
     }
 
     fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
-        if arg_types[0] == DataType::Utf8View {
-            Ok(DataType::Utf8View)
-        } else {
-            utf8_to_str_type(&arg_types[0], "rtrim")
-        }
+        Ok(arg_types[0].clone())
     }
 
     fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {

datafusion/functions/src/string/split_part.rs

@@ -24,8 +24,11 @@ use arrow::array::{AsArray, GenericStringBuilder};
 use arrow::datatypes::DataType;
 use datafusion_common::ScalarValue;
 use datafusion_common::cast::as_int64_array;
+use datafusion_common::types::{NativeType, logical_int64, logical_string};
 use datafusion_common::{DataFusionError, Result, exec_err};
-use datafusion_expr::{ColumnarValue, Documentation, TypeSignature, Volatility};
+use datafusion_expr::{
+    Coercion, ColumnarValue, Documentation, TypeSignatureClass, Volatility,
+};
 use datafusion_expr::{ScalarFunctionArgs, ScalarUDFImpl, Signature};
 use datafusion_macros::user_doc;
 use std::any::Any;
@@ -60,19 +63,16 @@ impl Default for SplitPartFunc {
 
 impl SplitPartFunc {
     pub fn new() -> Self {
-        use DataType::*;
         Self {
-            signature: Signature::one_of(
+            signature: Signature::coercible(
                 vec![
-                    TypeSignature::Exact(vec![Utf8View, Utf8View, Int64]),
-                    TypeSignature::Exact(vec![Utf8View, Utf8, Int64]),
-                    TypeSignature::Exact(vec![Utf8View, LargeUtf8, Int64]),
-                    TypeSignature::Exact(vec![Utf8, Utf8View, Int64]),
-                    TypeSignature::Exact(vec![Utf8, Utf8, Int64]),
-                    TypeSignature::Exact(vec![LargeUtf8, Utf8View, Int64]),
-                    TypeSignature::Exact(vec![LargeUtf8, Utf8, Int64]),
-                    TypeSignature::Exact(vec![Utf8, LargeUtf8, Int64]),
-                    TypeSignature::Exact(vec![LargeUtf8, LargeUtf8, Int64]),
+                    Coercion::new_exact(TypeSignatureClass::Native(logical_string())),
+                    Coercion::new_exact(TypeSignatureClass::Native(logical_string())),
+                    Coercion::new_implicit(
+                        TypeSignatureClass::Native(logical_int64()),
+                        vec![TypeSignatureClass::Integer],
+                        NativeType::Int64,
+                    ),
                 ],
                 Volatility::Immutable,
             ),

datafusion/functions/src/string/starts_with.rs

@@ -21,6 +21,7 @@ use std::sync::Arc;
 use arrow::array::{ArrayRef, Scalar};
 use arrow::compute::kernels::comparison::starts_with as arrow_starts_with;
 use arrow::datatypes::DataType;
+use datafusion_common::utils::take_function_args;
 use datafusion_expr::simplify::{ExprSimplifyResult, SimplifyInfo};
 use datafusion_expr::type_coercion::binary::{
     binary_to_string_coercion, string_coercion,
@@ -92,12 +93,7 @@ impl ScalarUDFImpl for StartsWithFunc {
     }
 
     fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
-        let [str_arg, prefix_arg] = args.args.as_slice() else {
-            return exec_err!(
-                "starts_with was called with {} arguments, expected 2",
-                args.args.len()
-            );
-        };
+        let [str_arg, prefix_arg] = take_function_args(self.name(), &args.args)?;
 
         // Determine the common type for coercion
         let coercion_type = string_coercion(

datafusion/functions/src/string/to_hex.rs

@@ -21,20 +21,16 @@ use std::sync::Arc;
 use crate::utils::make_scalar_function;
 use arrow::array::{Array, ArrayRef, StringArray};
 use arrow::buffer::{Buffer, OffsetBuffer};
-use arrow::datatypes::DataType::{
-    Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64, Utf8,
-};
 use arrow::datatypes::{
     ArrowNativeType, ArrowPrimitiveType, DataType, Int8Type, Int16Type, Int32Type,
     Int64Type, UInt8Type, UInt16Type, UInt32Type, UInt64Type,
 };
-use datafusion_common::Result;
 use datafusion_common::cast::as_primitive_array;
-use datafusion_common::{exec_err, plan_err};
-
-use datafusion_expr::{ColumnarValue, Documentation};
-use datafusion_expr::{ScalarFunctionArgs, ScalarUDFImpl, Signature, Volatility};
-use datafusion_expr_common::signature::TypeSignature::Exact;
+use datafusion_common::{Result, ScalarValue, exec_err};
+use datafusion_expr::{
+    Coercion, ColumnarValue, Documentation, ScalarFunctionArgs, ScalarUDFImpl, Signature,
+    TypeSignatureClass, Volatility,
+};
 use datafusion_macros::user_doc;
 
 /// Hex lookup table for fast conversion
@@ -201,17 +197,8 @@ impl Default for ToHexFunc {
 impl ToHexFunc {
     pub fn new() -> Self {
         Self {
-            signature: Signature::one_of(
-                vec![
-                    Exact(vec![Int8]),
-                    Exact(vec![Int16]),
-                    Exact(vec![Int32]),
-                    Exact(vec![Int64]),
-                    Exact(vec![UInt8]),
-                    Exact(vec![UInt16]),
-                    Exact(vec![UInt32]),
-                    Exact(vec![UInt64]),
-                ],
+            signature: Signature::coercible(
+                vec![Coercion::new_exact(TypeSignatureClass::Integer)],
                 Volatility::Immutable,
             ),
         }
@@ -231,25 +218,37 @@ impl ScalarUDFImpl for ToHexFunc {
         &self.signature
     }
 
-    fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
-        Ok(match arg_types[0] {
-            Int8 | Int16 | Int32 | Int64 | UInt8 | UInt16 | UInt32 | UInt64 => Utf8,
-            _ => {
-                return plan_err!("The to_hex function can only accept integers.");
-            }
-        })
+    fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
+        Ok(DataType::Utf8)
     }
 
     fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
         match args.args[0].data_type() {
-            Int64 => make_scalar_function(to_hex::<Int64Type>, vec![])(&args.args),
-            UInt64 => make_scalar_function(to_hex::<UInt64Type>, vec![])(&args.args),
-            Int32 => make_scalar_function(to_hex::<Int32Type>, vec![])(&args.args),
-            UInt32 => make_scalar_function(to_hex::<UInt32Type>, vec![])(&args.args),
-            Int16 => make_scalar_function(to_hex::<Int16Type>, vec![])(&args.args),
-            UInt16 => make_scalar_function(to_hex::<UInt16Type>, vec![])(&args.args),
-            Int8 => make_scalar_function(to_hex::<Int8Type>, vec![])(&args.args),
-            UInt8 => make_scalar_function(to_hex::<UInt8Type>, vec![])(&args.args),
+            DataType::Null => Ok(ColumnarValue::Scalar(ScalarValue::Utf8(None))),
+            DataType::Int64 => {
+                make_scalar_function(to_hex::<Int64Type>, vec![])(&args.args)
+            }
+            DataType::UInt64 => {
+                make_scalar_function(to_hex::<UInt64Type>, vec![])(&args.args)
+            }
+            DataType::Int32 => {
+                make_scalar_function(to_hex::<Int32Type>, vec![])(&args.args)
+            }
+            DataType::UInt32 => {
+                make_scalar_function(to_hex::<UInt32Type>, vec![])(&args.args)
+            }
+            DataType::Int16 => {
+                make_scalar_function(to_hex::<Int16Type>, vec![])(&args.args)
+            }
+            DataType::UInt16 => {
+                make_scalar_function(to_hex::<UInt16Type>, vec![])(&args.args)
+            }
+            DataType::Int8 => {
+                make_scalar_function(to_hex::<Int8Type>, vec![])(&args.args)
+            }
+            DataType::UInt8 => {
+                make_scalar_function(to_hex::<UInt8Type>, vec![])(&args.args)
+            }
             other => exec_err!("Unsupported data type {other:?} for function to_hex"),
         }
     }

datafusion/functions/src/string/uuid.rs

@@ -56,7 +56,7 @@ impl Default for UuidFunc {
 impl UuidFunc {
     pub fn new() -> Self {
         Self {
-            signature: Signature::exact(vec![], Volatility::Volatile),
+            signature: Signature::nullary(Volatility::Volatile),
         }
     }
 }

datafusion/sqllogictest/test_files/encoding.slt

@@ -73,7 +73,7 @@ select decode('', null) from test;
 query error DataFusion error: This feature is not implemented: Encoding must be a scalar; array specified encoding is not yet supported
 select decode('', hex_field) from test;
 
-query error DataFusion error: Error during planning: Failed to coerce arguments to satisfy a call to 'to_hex' function
+query error DataFusion error: Error during planning: Internal error: Expect TypeSignatureClass::Integer but received NativeType::String, DataType: Utf8View
 select to_hex(hex_field) from test;
 
 query error DataFusion error: Execution error: Failed to decode value using base64