[GitHub] [arrow] alamb commented on a change in pull request #9211: ARROW-11239: [Rust] Fixed equality of variable-sized arrays with offsets.

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

alamb commented on a change in pull request #9211:
URL: https://github.com/apache/arrow/pull/9211#discussion_r558844335



##########
File path: rust/arrow/src/array/equal/mod.rs
##########
@@ -541,6 +541,15 @@ mod tests {
         test_generic_binary_equal::<i64>()
     }
 
+    #[test]
+    fn test_string_offset() {
+        let a = StringArray::from(vec![Some("a"), None, Some("b")]).data();
+        let a = a.slice(2, 1);
+        let b = StringArray::from(vec![Some("b")]).data();
+
+        test_equal(&a, b.as_ref(), true);
+    }
+

Review comment:
       I may be missing something, but I tried a few more test cases and there still seems to be something wrong.
   
   Namely I would expect this test to pass:
   ```
       #[test]
       fn test_string_offset_larger() {
           let a = StringArray::from(vec![Some("a"), None, Some("b"), None, Some("c")]).data();
           let b = StringArray::from(vec![None, Some("b"), None, Some("c")]).data();
   
           test_equal(&a.slice(2,2), &b.slice(0,2), false);
           test_equal(&a.slice(2,2), &b.slice(1,2), true);
           test_equal(&a.slice(2,2), &b.slice(2,2), false);
       }
   ```
   
   But instead if fails 
   
   ```
   ---- array::equal::tests::test_string_offset_larger stdout ----
   thread 'array::equal::tests::test_string_offset_larger' panicked at 'assertion failed: `(left == right)`
     left: `false`,
    right: `true`: 
   ArrayData { data_type: Utf8, len: 2, null_count: 1, offset: 2, buffers: [Buffer { data: Bytes { ptr: 0x7fbc90504480, len: 24, data: [0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0] }, offset: 0 }, Buffer { data: Bytes { ptr: 0x7fbc90504500, len: 3, data: [97, 98, 99] }, offset: 0 }], child_data: [], null_bitmap: Some(Bitmap { bits: Buffer { data: Bytes { ptr: 0x7fbc90504580, len: 1, data: [21] }, offset: 0 } }) }
   ArrayData { data_type: Utf8, len: 2, null_count: 1, offset: 1, buffers: [Buffer { data: Bytes { ptr: 0x7fbc90604700, len: 20, data: [0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0] }, offset: 0 }, Buffer { data: Bytes { ptr: 0x7fbc90604880, len: 2, data: [98, 99] }, offset: 0 }], child_data: [], null_bitmap: Some(Bitmap { bits: Buffer { data: Bytes { ptr: 0x7fbc90604780, len: 1, data: [10] }, offset: 0 } }) }', arrow/src/array/equal/mod.rs:457:9
   note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
   ```




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