[GitHub] [arrow-datafusion] alamb commented on a change in pull request #1554: support mathematics operation for decimal data type

[GitBox <gi...@apache.org>]

alamb commented on a change in pull request #1554:
URL: https://github.com/apache/arrow-datafusion/pull/1554#discussion_r786034055



##########
File path: datafusion/src/physical_plan/coercion_rule/binary_rule.rs
##########
@@ -162,12 +162,141 @@ fn get_comparison_common_decimal_type(
     }
 }
 
+// Convert the numeric data type to the decimal data type.
+// Now, we just support the signed integer type and floating-point type.
+fn convert_numeric_type_to_decimal(numeric_type: &DataType) -> Option<DataType> {
+    match numeric_type {
+        DataType::Int8 => Some(DataType::Decimal(3, 0)),
+        DataType::Int16 => Some(DataType::Decimal(5, 0)),
+        DataType::Int32 => Some(DataType::Decimal(10, 0)),
+        DataType::Int64 => Some(DataType::Decimal(20, 0)),
+        // TODO if we convert the floating-point data to the decimal type, it maybe overflow.
+        DataType::Float32 => Some(DataType::Decimal(14, 7)),
+        DataType::Float64 => Some(DataType::Decimal(30, 15)),
+        _ => None,
+    }
+}
+
+fn mathematics_numerical_coercion(

Review comment:
       This function looks almost the same as `numerical_coercion`  -- which is used for equality
   
   What is the reason for making a new function rather than extending `numerical_coercion` with Decimal support?

##########
File path: datafusion/src/physical_plan/expressions/binary.rs
##########
@@ -235,12 +236,10 @@ fn is_distinct_from_decimal(
 ) -> Result<BooleanArray> {
     let mut bool_builder = BooleanBuilder::new(left.len());
     for i in 0..left.len() {
-        if left.is_null(i) && right.is_null(i) {
-            bool_builder.append_value(false)?;
-        } else if left.is_null(i) || right.is_null(i) {
-            bool_builder.append_value(true)?;
-        } else {
-            bool_builder.append_value(left.value(i) != right.value(i))?;
+        match (left.is_null(i), right.is_null(i)) {

Review comment:
       👍 

##########
File path: datafusion/src/physical_plan/coercion_rule/binary_rule.rs
##########
@@ -162,12 +162,141 @@ fn get_comparison_common_decimal_type(
     }
 }
 
+// Convert the numeric data type to the decimal data type.
+// Now, we just support the signed integer type and floating-point type.
+fn convert_numeric_type_to_decimal(numeric_type: &DataType) -> Option<DataType> {

Review comment:
       maybe this would be better called `coerce_numeric_type_to_decimal`?




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