[GitHub] [arrow-rs] liukun4515 commented on a diff in pull request #2446: collation the validate precision code for decimal array

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

liukun4515 commented on code in PR #2446:
URL: https://github.com/apache/arrow-rs/pull/2446#discussion_r945647574


##########
arrow/src/array/array_decimal.rs:
##########
@@ -316,26 +300,67 @@ impl Decimal128Array {
                 scale, precision
             )));
         }
-
-        // Ensure that all values are within the requested
-        // precision. For performance, only check if the precision is
-        // decreased
-        if precision < self.precision {
-            self.validate_decimal_precision(precision)?;
-        }
-
         let data_type = Self::TYPE_CONSTRUCTOR(self.precision, self.scale);
         assert_eq!(self.data().data_type(), &data_type);
 
-        // safety: self.data is valid DataType::Decimal as checked above
-        let new_data_type = Self::TYPE_CONSTRUCTOR(precision, scale);
+        Ok(())
+    }
+
+    // validate all the data in the array are valid within the new precision or not
+    fn validate_data(&self, precision: usize) -> Result<()> {
+        match BYTE_WIDTH {
+            16 => self
+                .as_any()
+                .downcast_ref::<Decimal128Array>()
+                .unwrap()
+                .validate_decimal_precision(precision),
+            32 => self
+                .as_any()
+                .downcast_ref::<Decimal256Array>()
+                .unwrap()
+                .validate_decimal_precision(precision),
+            other_width => {
+                panic!("invalid byte width {}", other_width);

Review Comment:
   I don't test this error.
   Guess this is a runtime error, when use `BasicDecimalArray<OTHER_WIDTH>` to call this method.



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