[GitHub] [arrow-rs] alamb commented on a change in pull request #273: Added Decimal support to pretty-print display utility (#230)

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

alamb commented on a change in pull request #273:
URL: https://github.com/apache/arrow-rs/pull/273#discussion_r629255080



##########
File path: arrow/src/util/display.rs
##########
@@ -296,3 +297,48 @@ fn dict_array_value_to_string<K: ArrowPrimitiveType>(
 
     array_value_to_string(&dict_array.values(), dict_index)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{
+        array::ArrayRef,
+        array::{ArrayData, DecimalArray, Int32Array},
+    };
+    use crate::{buffer::Buffer, datatypes::DataType};
+    use std::sync::Arc;
+
+    #[test]
+    fn test_int_display() -> Result<()> {
+        let array = Arc::new(Int32Array::from(vec![6, 3])) as ArrayRef;
+        let actual_one = array_value_to_string(&array, 0).unwrap();
+        let expected_one = String::from("6");

Review comment:
       ```suggestion
           let expected_one = "6";
   ```
   
   I don't think you need to create a `String` you can just compare with the `&str`

##########
File path: arrow/src/util/display.rs
##########
@@ -296,3 +297,48 @@ fn dict_array_value_to_string<K: ArrowPrimitiveType>(
 
     array_value_to_string(&dict_array.values(), dict_index)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{
+        array::ArrayRef,
+        array::{ArrayData, DecimalArray, Int32Array},
+    };
+    use crate::{buffer::Buffer, datatypes::DataType};
+    use std::sync::Arc;
+
+    #[test]
+    fn test_int_display() -> Result<()> {
+        let array = Arc::new(Int32Array::from(vec![6, 3])) as ArrayRef;
+        let actual_one = array_value_to_string(&array, 0).unwrap();
+        let expected_one = String::from("6");
+
+        let actual_two = array_value_to_string(&array, 1).unwrap();
+        let expected_two = String::from("3");
+        assert_eq!(actual_one, expected_one);
+        assert_eq!(actual_two, expected_two);
+        Ok(())
+    }
+
+    #[test]
+    fn test_decimal_display() -> Result<()> {
+        let values: [u8; 32] = [

Review comment:
       This is a pretty low level way to make a `DecimalArray`
   
   What would you think of using the `DecimalBuilder` -- something like the following
   
   ```
           let capacity = 10;
           let precision = 10; // total number of digits
           let scale = 2; // 2 digits after the decimal point
           let mut builder = DecimalBuilder::new(capacity, precision, scale);
           builder.append_value(101).unwrap();
           builder.append_null().unwrap();
           builder.append_value(200).unwrap();
           builder.append_value(3040).unwrap();
   
           let dm = Arc::new(builder.finish()) as ArrayRef;
   ```
   
   
   Note in this case, I would expect the display values to be something like the following (always have 2 decimal places):
   ```
   1.01
   
   2.00
   30.40
   ```
   
   

##########
File path: arrow/src/util/display.rs
##########
@@ -296,3 +297,48 @@ fn dict_array_value_to_string<K: ArrowPrimitiveType>(
 
     array_value_to_string(&dict_array.values(), dict_index)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{
+        array::ArrayRef,
+        array::{ArrayData, DecimalArray, Int32Array},
+    };
+    use crate::{buffer::Buffer, datatypes::DataType};
+    use std::sync::Arc;
+
+    #[test]

Review comment:
       There are a few more tests of `pretty-printing` which uses this display code in https://github.com/apache/arrow-rs/blob/master/arrow/src/util/pretty.rs#L229 
   
   You might find writing tests following that style (perhaps putting the tests in that module) easier

##########
File path: arrow/src/util/display.rs
##########
@@ -296,3 +297,48 @@ fn dict_array_value_to_string<K: ArrowPrimitiveType>(
 
     array_value_to_string(&dict_array.values(), dict_index)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{
+        array::ArrayRef,
+        array::{ArrayData, DecimalArray, Int32Array},
+    };
+    use crate::{buffer::Buffer, datatypes::DataType};
+    use std::sync::Arc;
+
+    #[test]
+    fn test_int_display() -> Result<()> {
+        let array = Arc::new(Int32Array::from(vec![6, 3])) as ArrayRef;
+        let actual_one = array_value_to_string(&array, 0).unwrap();
+        let expected_one = String::from("6");
+
+        let actual_two = array_value_to_string(&array, 1).unwrap();
+        let expected_two = String::from("3");

Review comment:
       ```suggestion
           let expected_two = "3";
   ```




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