Convert nth_value to UDAF

datafusion/expr/src/aggregate_function.rs

@@ -39,8 +39,6 @@ pub enum AggregateFunction {
     Max,
     /// Aggregation into an array
     ArrayAgg,
-    /// N'th value in a group according to some ordering
-    NthValue,
 }
 
 impl AggregateFunction {
@@ -50,7 +48,6 @@ impl AggregateFunction {
             Min => "MIN",
             Max => "MAX",
             ArrayAgg => "ARRAY_AGG",
-            NthValue => "NTH_VALUE",
         }
     }
 }
@@ -69,7 +66,6 @@ impl FromStr for AggregateFunction {
             "max" => AggregateFunction::Max,
             "min" => AggregateFunction::Min,
             "array_agg" => AggregateFunction::ArrayAgg,
-            "nth_value" => AggregateFunction::NthValue,
             _ => {
                 return plan_err!("There is no built-in function named {name}");
             }
@@ -114,7 +110,6 @@ impl AggregateFunction {
                 coerced_data_types[0].clone(),
                 input_expr_nullable[0],
             )))),
-            AggregateFunction::NthValue => Ok(coerced_data_types[0].clone()),
         }
     }
 
@@ -124,7 +119,6 @@ impl AggregateFunction {
         match self {
             AggregateFunction::Max | AggregateFunction::Min => Ok(true),
             AggregateFunction::ArrayAgg => Ok(false),
-            AggregateFunction::NthValue => Ok(true),
         }
     }
 }
@@ -147,7 +141,6 @@ impl AggregateFunction {
                     .collect::<Vec<_>>();
                 Signature::uniform(1, valid, Volatility::Immutable)
             }
-            AggregateFunction::NthValue => Signature::any(2, Volatility::Immutable),
         }
     }
 }

datafusion/expr/src/type_coercion/aggregates.rs

@@ -101,7 +101,6 @@ pub fn coerce_types(
             // unpack the dictionary to get the value
             get_min_max_result_type(input_types)
         }
-        AggregateFunction::NthValue => Ok(input_types.to_vec()),
     }
 }
 

datafusion/functions-aggregate/src/lib.rs

@@ -74,6 +74,7 @@ pub mod average;
 pub mod bit_and_or_xor;
 pub mod bool_and_or;
 pub mod grouping;
+pub mod nth_value;
 pub mod string_agg;
 
 use crate::approx_percentile_cont::approx_percentile_cont_udaf;
@@ -105,6 +106,7 @@ pub mod expr_fn {
     pub use super::first_last::last_value;
     pub use super::grouping::grouping;
     pub use super::median::median;
+    pub use super::nth_value::nth_value;
     pub use super::regr::regr_avgx;
     pub use super::regr::regr_avgy;
     pub use super::regr::regr_count;
@@ -157,6 +159,7 @@ pub fn all_default_aggregate_functions() -> Vec<Arc<AggregateUDF>> {
         bool_and_or::bool_or_udaf(),
         average::avg_udaf(),
         grouping::grouping_udaf(),
+        nth_value::nth_value_udaf(),
     ]
 }