jayzhan211 commented on code in PR #11013:
URL: https://github.com/apache/datafusion/pull/11013#discussion_r1700177718


##########
datafusion/functions-aggregate/src/min_max.rs:
##########
@@ -15,103 +15,165 @@
 // specific language governing permissions and limitations
 // under the License.
 
-//! Defines physical expressions that can evaluated at runtime during query 
execution
+//! [`Max`] and [`MaxAccumulator`] accumulator for the `max` function
+//! [`Min`] and [`MinAccumulator`] accumulator for the `max` function
 
-use std::any::Any;
-use std::sync::Arc;
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
 
-use crate::aggregate::groups_accumulator::prim_op::PrimitiveGroupsAccumulator;
-use crate::{AggregateExpr, PhysicalExpr};
+use arrow::array::{
+    ArrayRef, BinaryArray, BooleanArray, Date32Array, Date64Array, 
Decimal128Array,
+    Decimal256Array, Float32Array, Float64Array, Int16Array, Int32Array, 
Int64Array,
+    Int8Array, IntervalDayTimeArray, IntervalMonthDayNanoArray, 
IntervalYearMonthArray,
+    LargeBinaryArray, LargeStringArray, StringArray, Time32MillisecondArray,
+    Time32SecondArray, Time64MicrosecondArray, Time64NanosecondArray,
+    TimestampMicrosecondArray, TimestampMillisecondArray, 
TimestampNanosecondArray,
+    TimestampSecondArray, UInt16Array, UInt32Array, UInt64Array, UInt8Array,
+};
 use arrow::compute;
 use arrow::datatypes::{
-    DataType, Date32Type, Date64Type, IntervalUnit, Time32MillisecondType,
-    Time32SecondType, Time64MicrosecondType, Time64NanosecondType, TimeUnit,
-    TimestampMicrosecondType, TimestampMillisecondType, 
TimestampNanosecondType,
-    TimestampSecondType,
-};
-use arrow::{
-    array::{
-        ArrayRef, BinaryArray, BooleanArray, Date32Array, Date64Array, 
Float32Array,
-        Float64Array, Int16Array, Int32Array, Int64Array, Int8Array,
-        IntervalDayTimeArray, IntervalMonthDayNanoArray, 
IntervalYearMonthArray,
-        LargeBinaryArray, LargeStringArray, StringArray, 
Time32MillisecondArray,
-        Time32SecondArray, Time64MicrosecondArray, Time64NanosecondArray,
-        TimestampMicrosecondArray, TimestampMillisecondArray, 
TimestampNanosecondArray,
-        TimestampSecondArray, UInt16Array, UInt32Array, UInt64Array, 
UInt8Array,
-    },
-    datatypes::Field,
+    DataType, Decimal128Type, Decimal256Type, Float32Type, Float64Type, 
Int16Type,
+    Int32Type, Int64Type, Int8Type, UInt16Type, UInt32Type, UInt64Type, 
UInt8Type,
 };
-use arrow_array::types::{
-    Decimal128Type, Float32Type, Float64Type, Int16Type, Int32Type, Int64Type, 
Int8Type,
-    UInt16Type, UInt32Type, UInt64Type, UInt8Type,
-};
-use arrow_array::{BinaryViewArray, StringViewArray};
-use datafusion_common::internal_err;
-use datafusion_common::ScalarValue;
-use datafusion_common::{downcast_value, DataFusionError, Result};
-use datafusion_expr::{Accumulator, GroupsAccumulator};
-
-use crate::aggregate::utils::down_cast_any_ref;
-use crate::expressions::format_state_name;
-use arrow::array::Array;
-use arrow::array::Decimal128Array;
-use arrow::array::Decimal256Array;
+use arrow_schema::IntervalUnit;
+use datafusion_common::{downcast_value, internal_err, DataFusionError, Result};
+use 
datafusion_physical_expr_common::aggregate::groups_accumulator::prim_op::PrimitiveGroupsAccumulator;
+use std::fmt::Debug;
+
 use arrow::datatypes::i256;
-use arrow::datatypes::Decimal256Type;
+use arrow::datatypes::{
+    Date32Type, Date64Type, Time32MillisecondType, Time32SecondType,
+    Time64MicrosecondType, Time64NanosecondType, TimeUnit, 
TimestampMicrosecondType,
+    TimestampMillisecondType, TimestampNanosecondType, TimestampSecondType,
+};
 
-use super::moving_min_max;
+use datafusion_common::ScalarValue;
+use datafusion_expr::{
+    function::AccumulatorArgs, Accumulator, AggregateUDFImpl, Signature, 
Volatility,
+};
+use datafusion_expr::{type_coercion, Expr, GroupsAccumulator};
+
+pub static STRINGS: &[DataType] = &[DataType::Utf8, DataType::LargeUtf8];

Review Comment:
   Actually udaf and builtin goes to different path. Builtin in 
`coerce_agg_exprs_for_signature`, UDAF in 
`coerce_arguments_for_signature_with_aggregate_udf`. Directly moving the 
builtin signature to UDAF make things complicated.
   
   After you coerce with `user_defined`, `coerce_types` tell you what is 
actually happening. It makes coercion of the function a lot easier and trivial. 
Although ideally, this is only for function that has specialized need, others 
function should use datafusion's builtin signature (which sadly is not easy to 
use yet).
   
   The `coerce_types` is called 
[here](https://github.com/apache/datafusion/blob/3fe18604e8a127dbecf78acff0dce7596790bfe8/datafusion/expr/src/type_coercion/functions.rs#L190-L194)
   
   You can trace the code to understand how the data types are coerced and send 
to `return_type`.
   
   



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