Move functionality into BuildInScalarFunction (#6612)

Author: alamb

datafusion/expr/src/built_in_function.rs

@@ -22,9 +22,7 @@ use crate::expr::{
 };
 use crate::field_util::get_indexed_field;
 use crate::type_coercion::binary::get_result_type;
-use crate::{
-    aggregate_function, function, window_function, LogicalPlan, Projection, Subquery,
-};
+use crate::{aggregate_function, window_function, LogicalPlan, Projection, Subquery};
 use arrow::compute::can_cast_types;
 use arrow::datatypes::DataType;
 use datafusion_common::{Column, DFField, DFSchema, DataFusionError, ExprSchema, Result};
@@ -87,7 +85,7 @@ impl ExprSchemable for Expr {
                     .iter()
                     .map(|e| e.get_type(schema))
                     .collect::<Result<Vec<_>>>()?;
-                function::return_type(fun, &data_types)
+                fun.return_type(&data_types)
             }
             Expr::WindowFunction(WindowFunction { fun, args, .. }) => {
                 let data_types = args

datafusion/expr/src/expr_schema.rs

@@ -37,7 +37,6 @@ pub mod expr_rewriter;
 pub mod expr_schema;
 pub mod field_util;
 pub mod function;
-pub mod function_err;
 mod literal;
 pub mod logical_plan;
 mod nullif;

datafusion/expr/src/function.rs

@@ -60,6 +60,48 @@ pub enum TypeSignature {
     OneOf(Vec<TypeSignature>),
 }
 
+impl TypeSignature {
+    pub(crate) fn to_string_repr(&self) -> Vec<String> {
+        match self {
+            TypeSignature::Variadic(types) => {
+                vec![format!("{}, ..", Self::join_types(types, "/"))]
+            }
+            TypeSignature::Uniform(arg_count, valid_types) => {
+                vec![std::iter::repeat(Self::join_types(valid_types, "/"))
+                    .take(*arg_count)
+                    .collect::<Vec<String>>()
+                    .join(", ")]
+            }
+            TypeSignature::Exact(types) => {
+                vec![Self::join_types(types, ", ")]
+            }
+            TypeSignature::Any(arg_count) => {
+                vec![std::iter::repeat("Any")
+                    .take(*arg_count)
+                    .collect::<Vec<&str>>()
+                    .join(", ")]
+            }
+            TypeSignature::VariadicEqual => vec!["T, .., T".to_string()],
+            TypeSignature::VariadicAny => vec!["Any, .., Any".to_string()],
+            TypeSignature::OneOf(sigs) => {
+                sigs.iter().flat_map(|s| s.to_string_repr()).collect()
+            }
+        }
+    }
+
+    /// Helper function to join types with specified delimiter.
+    pub(crate) fn join_types<T: std::fmt::Display>(
+        types: &[T],
+        delimiter: &str,
+    ) -> String {
+        types
+            .iter()
+            .map(|t| t.to_string())
+            .collect::<Vec<String>>()
+            .join(delimiter)
+    }
+}
+
 /// The signature of a function defines the supported argument types
 /// and its volatility.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]

datafusion/expr/src/function_err.rs

@@ -40,8 +40,8 @@ use datafusion_expr::type_coercion::other::{
 use datafusion_expr::type_coercion::{is_datetime, is_numeric, is_utf8_or_large_utf8};
 use datafusion_expr::utils::from_plan;
 use datafusion_expr::{
-    aggregate_function, function, is_false, is_not_false, is_not_true, is_not_unknown,
-    is_true, is_unknown, type_coercion, AggregateFunction, Expr, LogicalPlan, Operator,
+    aggregate_function, is_false, is_not_false, is_not_true, is_not_unknown, is_true,
+    is_unknown, type_coercion, AggregateFunction, Expr, LogicalPlan, Operator,
     Projection, WindowFrame, WindowFrameBound, WindowFrameUnits,
 };
 use datafusion_expr::{ExprSchemable, Signature};
@@ -390,7 +390,7 @@ impl TreeNodeRewriter for TypeCoercionRewriter {
                 let nex_expr = coerce_arguments_for_signature(
                     args.as_slice(),
                     &self.schema,
-                    &function::signature(&fun),
+                    &fun.signature(),
                 )?;
                 let expr = Expr::ScalarFunction(ScalarFunction::new(fun, nex_expr));
                 Ok(expr)

datafusion/expr/src/lib.rs

@@ -45,7 +45,7 @@ use arrow::{
 };
 use datafusion_common::{DataFusionError, Result, ScalarValue};
 use datafusion_expr::{
-    function, BuiltinScalarFunction, ColumnarValue, ScalarFunctionImplementation,
+    BuiltinScalarFunction, ColumnarValue, ScalarFunctionImplementation,
 };
 use std::sync::Arc;
 
@@ -62,7 +62,7 @@ pub fn create_physical_expr(
         .map(|e| e.data_type(input_schema))
         .collect::<Result<Vec<_>>>()?;
 
-    let data_type = function::return_type(fun, &input_expr_types)?;
+    let data_type = fun.return_type(&input_expr_types)?;
 
     let fun_expr: ScalarFunctionImplementation = match fun {
         // These functions need args and input schema to pick an implementation
@@ -2921,7 +2921,7 @@ mod tests {
         execution_props: &ExecutionProps,
     ) -> Result<Arc<dyn PhysicalExpr>> {
         let type_coerced_phy_exprs =
-            coerce(input_phy_exprs, input_schema, &function::signature(fun)).unwrap();
+            coerce(input_phy_exprs, input_schema, &fun.signature()).unwrap();
         create_physical_expr(fun, &type_coerced_phy_exprs, input_schema, execution_props)
     }
 

datafusion/expr/src/signature.rs

@@ -18,7 +18,7 @@
 use crate::planner::{ContextProvider, PlannerContext, SqlToRel};
 use datafusion_common::{DFSchema, DataFusionError, Result};
 use datafusion_expr::expr::{ScalarFunction, ScalarUDF};
-use datafusion_expr::function_err::suggest_valid_function;
+use datafusion_expr::function::suggest_valid_function;
 use datafusion_expr::utils::COUNT_STAR_EXPANSION;
 use datafusion_expr::window_frame::regularize;
 use datafusion_expr::{