[GitHub] [arrow] sweb commented on a change in pull request #9047: ARROW-11072: [Rust] [Parquet] Support reading decimal from physical int types

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

sweb commented on a change in pull request #9047:
URL: https://github.com/apache/arrow/pull/9047#discussion_r550468948



##########
File path: rust/parquet/src/arrow/schema.rs
##########
@@ -657,6 +645,22 @@ impl ParquetTypeConverter<'_> {
         }
     }
 
+    fn to_decimal(&self) -> Result<DataType> {
+        let (precision, scale) = match self.schema {
+            Type::PrimitiveType {
+                ref precision,
+                ref scale,
+                ..
+            } => (*precision, *scale),
+            _ => {
+                return Err(ArrowError(

Review comment:
       @sunchao thank you for your review comments! I changed this part as suggested. Do you have an example of an assertion checking for a type? The only thing I could come up with (still quite new to Rust) is something along the lines of
   
   ```
   if let Type::PrimitiveType {ref precision, ref scale, .. } = self.schema {
     DataType::Decimal(*precision as usize, *scale as usize)
   } else {
     panic!("Expected a physical type, not a group type")
   }
   ```




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