[GitHub] [arrow-rs] HaoYang670 commented on a diff in pull request #2357: [WIP]Change precision of decimal without validation

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

HaoYang670 commented on code in PR #2357:
URL: https://github.com/apache/arrow-rs/pull/2357#discussion_r940106398


##########
arrow/src/compute/kernels/cast.rs:
##########
@@ -1276,8 +1277,17 @@ fn cast_decimal_to_decimal(
             .iter()
             .map(|v| v.map(|v| v.as_i128() * mul))
             .collect::<Decimal128Array>()
-    }
-    .with_precision_and_scale(*output_precision, *output_scale)?;
+    };
+    // For decimal cast to decimal, if the range of output is gt_eq than the input, don't need to
+    // do validation.
+    let output_array  = match output_precision-output_scale>=input_precision - input_scale {
+        true => {
+            output_array.with_precision_and_scale(*output_precision, *output_scale, false)
+        }
+        false => {
+            output_array.with_precision_and_scale(*output_precision, *output_scale, true)
+        }
+    }?;

Review Comment:
   I am still learning the logic. Here is just a nit:
   ```suggestion
       let output_array  = output_array.with_precision_and_scale(
           *output_precision, 
           *output_scale, 
           output_precision - output_scale < input_precision - input_scale)?;
   ```



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