[jira] [Created] (ARROW-8508) [Rust] ListBuilder of FixedSizeListBuilder creates wrong offsets

[Christian Beilschmidt (Jira)]

Christian Beilschmidt created ARROW-8508:
--------------------------------------------

             Summary: [Rust] ListBuilder of FixedSizeListBuilder creates wrong 
offsets
                 Key: ARROW-8508
                 URL: https://issues.apache.org/jira/browse/ARROW-8508
             Project: Apache Arrow
          Issue Type: Bug
          Components: Rust
    Affects Versions: 0.16.0
            Reporter: Christian Beilschmidt


I created an example of storing multi points with Arrow.
 # A coordinate consists of two floats (Float64Builder)
 # A multi point consists of one or more coordinates (FixedSizeListBuilder)
 # A list of multi points consists of multiple multi points (ListBuilder)

This is the corresponding code snippet:
{code:java}
let float_builder = arrow::array::Float64Builder::new(0);
let coordinate_builder = arrow::array::FixedSizeListBuilder::new(float_builder, 
2);
let mut multi_point_builder = 
arrow::array::ListBuilder::new(coordinate_builder);

multi_point_builder
    .values()
    .values()
    .append_slice(&[0.0, 0.1])
    .unwrap();
multi_point_builder.values().append(true).unwrap();
multi_point_builder
    .values()
    .values()
    .append_slice(&[1.0, 1.1])
    .unwrap();
multi_point_builder.values().append(true).unwrap();

multi_point_builder.append(true).unwrap(); // first multi point

multi_point_builder
    .values()
    .values()
    .append_slice(&[2.0, 2.1])
    .unwrap();
multi_point_builder.values().append(true).unwrap();
multi_point_builder
    .values()
    .values()
    .append_slice(&[3.0, 3.1])
    .unwrap();
multi_point_builder.values().append(true).unwrap();
multi_point_builder
    .values()
    .values()
    .append_slice(&[4.0, 4.1])
    .unwrap();
multi_point_builder.values().append(true).unwrap();

multi_point_builder.append(true).unwrap(); // second multi point

let multi_point = dbg!(multi_point_builder.finish());

let first_multi_point_ref = multi_point.value(0);
let first_multi_point: &arrow::array::FixedSizeListArray = 
first_multi_point_ref.as_any().downcast_ref().unwrap();
let coordinates_ref = first_multi_point.values();
let coordinates: &Float64Array = 
coordinates_ref.as_any().downcast_ref().unwrap();

assert_eq!(coordinates.value_slice(0, 2 * 2), &[0.0, 0.1, 1.0, 1.1]);

let second_multi_point_ref = multi_point.value(1);
let second_multi_point: &arrow::array::FixedSizeListArray = 
second_multi_point_ref.as_any().downcast_ref().unwrap();
let coordinates_ref = second_multi_point.values();
let coordinates: &Float64Array = 
coordinates_ref.as_any().downcast_ref().unwrap();

assert_eq!(coordinates.value_slice(0, 2 * 3), &[2.0, 2.1, 3.0, 3.1, 4.0, 4.1]);
{code}
The second assertion fails and the output is {{[0.0, 0.1, 1.0, 1.1, 2.0, 2.1]}}.

Moreover, the debug output produced from {{dbg!}} confirms this:
{noformat}
[
  FixedSizeListArray<2>
[
  PrimitiveArray<Float64>
[
  0.0,
  0.1,
],
  PrimitiveArray<Float64>
[
  1.0,
  1.1,
],
],
  FixedSizeListArray<2>
[
  PrimitiveArray<Float64>
[
  0.0,
  0.1,
],
  PrimitiveArray<Float64>
[
  1.0,
  1.1,
],
  PrimitiveArray<Float64>
[
  2.0,
  2.1,
],
],
]{noformat}
The second list should contain the values 2-4.

 

So either I am using the builder wrong or there is a bug with the offsets. I 
used {{0.16}} as well as the current {{master}} from GitHub.



--
This message was sent by Atlassian Jira
(v8.3.4#803005)