[GitHub] [arrow-datafusion] jackwener commented on a diff in pull request #6250: refactor: separate result type into new file

["jackwener (via GitHub)" <gi...@apache.org>]

jackwener commented on code in PR #6250:
URL: https://github.com/apache/arrow-datafusion/pull/6250#discussion_r1186025382


##########
datafusion/expr/src/type_coercion/binary_result_type.rs:
##########
@@ -0,0 +1,149 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// 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.
+
+//! Coercion rules for matching argument types for binary operators
+
+use arrow::datatypes::DataType;
+
+use datafusion_common::DataFusionError;
+use datafusion_common::Result;
+
+use crate::type_coercion::binary::{
+    any_decimal, bitwise_coercion, decimal_op_mathematics_type, math_decimal_coercion,
+    mathematics_numerical_coercion, string_concat_coercion, mathematics_temporal_common_type,
+};
+use crate::type_coercion::{is_datetime, is_interval};
+use crate::Operator;
+
+/// returns the resulting type of a binary expression evaluating the `op` with the left and right hand types
+pub fn get_result_type(
+    lhs_type: &DataType,
+    op: &Operator,
+    rhs_type: &DataType,
+) -> Result<DataType> {
+    if op.is_numerical_operators() && any_decimal(lhs_type, rhs_type) {
+        let (coerced_lhs_type, coerced_rhs_type) =
+            math_decimal_coercion(lhs_type, rhs_type);
+
+        let lhs_type = coerced_lhs_type.unwrap_or(lhs_type.clone());
+        let rhs_type = coerced_rhs_type.unwrap_or(rhs_type.clone());
+
+        if op.is_numerical_operators() {
+            if let Some(result_type) =
+                decimal_op_mathematics_type(op, &lhs_type, &rhs_type)
+            {
+                return Ok(result_type);
+            }
+        }
+    }
+    let result = match op {
+        Operator::And
+        | Operator::Or
+        | Operator::Eq
+        | Operator::NotEq
+        | Operator::Lt
+        | Operator::Gt
+        | Operator::GtEq
+        | Operator::LtEq
+        | Operator::RegexMatch
+        | Operator::RegexIMatch
+        | Operator::RegexNotMatch
+        | Operator::RegexNotIMatch
+        | Operator::IsDistinctFrom
+        | Operator::IsNotDistinctFrom => Some(DataType::Boolean),
+        Operator::Plus | Operator::Minus
+            if is_datetime(lhs_type) && is_datetime(rhs_type)
+                || (is_interval(lhs_type) && is_interval(rhs_type))
+                || (is_datetime(lhs_type) && is_interval(rhs_type))
+                || (is_interval(lhs_type) && is_datetime(rhs_type)) =>
+        {
+            mathematics_temporal_result_type(lhs_type, rhs_type)
+        }
+        // following same with `coerce_types`
+        Operator::BitwiseAnd
+        | Operator::BitwiseOr
+        | Operator::BitwiseXor
+        | Operator::BitwiseShiftRight
+        | Operator::BitwiseShiftLeft => bitwise_coercion(lhs_type, rhs_type),
+        Operator::Plus
+        | Operator::Minus
+        | Operator::Modulo
+        | Operator::Divide
+        | Operator::Multiply => mathematics_numerical_coercion(lhs_type, rhs_type),
+        Operator::StringConcat => string_concat_coercion(lhs_type, rhs_type),
+    };
+
+    result.ok_or(DataFusionError::Plan(format!(
+        "Unsupported argument types. Can not evaluate {lhs_type:?} {op} {rhs_type:?}"
+    )))
+}
+
+/// Returns the result type of applying mathematics operations such as
+/// `+` to arguments of `lhs_type` and `rhs_type`.
+fn mathematics_temporal_result_type(
+    lhs_type: &DataType,
+    rhs_type: &DataType,
+) -> Option<DataType> {
+    use arrow::datatypes::DataType::*;
+    use arrow::datatypes::IntervalUnit::*;
+    use arrow::datatypes::TimeUnit::*;
+
+    // error on any temporal type
+    if !is_interval(lhs_type)
+        && !is_interval(rhs_type)
+        && !is_datetime(lhs_type)
+        && !is_datetime(rhs_type)
+    {
+        return None;
+    };
+
+    match (lhs_type, rhs_type) {
+        // datetime +/- interval
+        (Interval(_), Timestamp(_, _)) => Some(rhs_type.clone()),
+        (Timestamp(_, _), Interval(_)) => Some(lhs_type.clone()),
+        (Interval(_), Date32) => Some(rhs_type.clone()),
+        (Date32, Interval(_)) => Some(lhs_type.clone()),
+        (Interval(_), Date64) => Some(rhs_type.clone()),
+        (Date64, Interval(_)) => Some(lhs_type.clone()),
+        // interval +/-
+        (Interval(YearMonth), Interval(YearMonth)) => Some(Interval(YearMonth)),
+        (Interval(DayTime), Interval(DayTime)) => Some(Interval(DayTime)),
+        (Interval(_), Interval(_)) => Some(Interval(MonthDayNano)),
+        // timestamp - timestamp
+        (Timestamp(Second, _), Timestamp(Second, _))
+        | (Timestamp(Millisecond, _), Timestamp(Millisecond, _)) => {
+            Some(Interval(DayTime))
+        }
+        (Timestamp(Microsecond, _), Timestamp(Microsecond, _))
+        | (Timestamp(Nanosecond, _), Timestamp(Nanosecond, _)) => {
+            Some(Interval(MonthDayNano))
+        }
+        (Timestamp(_, _), Timestamp(_, _)) => None,
+        // TODO: date minus date
+        // date - timestamp, timestamp - date
+        (Date32, Timestamp(_, _))
+        | (Timestamp(_, _), Date32)
+        | (Date64, Timestamp(_, _))
+        | (Timestamp(_, _), Date64) => {
+            // TODO: make get_result_type must after coerce type.
+            // if type isn't coerced, we need get common type, and then get result type.
+            let common_type = mathematics_temporal_common_type(lhs_type, rhs_type);
+            common_type.and_then(|t| mathematics_temporal_result_type(&t, &t))

Review Comment:
   it's related a comment from @alamb in https://github.com/apache/arrow-datafusion/issues/6223



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