ARROW-10042: [Rust] Only compare BufferData's data for equality

And disregard differences in capacity.

rust/arrow/src/buffer.rs

@@ -70,10 +70,6 @@ struct BufferData {
 
 impl PartialEq for BufferData {
     fn eq(&self, other: &BufferData) -> bool {
-        if self.capacity != other.capacity {
-            return false;
-        }
-
         self.data() == other.data()
     }
 }
@@ -855,6 +851,19 @@ mod tests {
         assert_ne!(buf1, buf2);
     }
 
+    #[test]
+    fn buffer_data_equality_checks_data_not_capacity() {
+        let buf1 = Buffer::from(&[0, 1, 2, 3, 4]);
+
+        let mut buf2 = MutableBuffer::new(65);
+        buf2.write_all(&[0, 1, 2, 3, 4])
+            .expect("write should be OK");
+
+        let buf2 = buf2.freeze();
+
+        assert_eq!(buf1, buf2);
+    }
+
     #[test]
     fn test_from_raw_parts() {
         let buf = unsafe { Buffer::from_raw_parts(null_mut(), 0, 0) };

rust/parquet/src/arrow/arrow_writer.rs

@@ -1202,7 +1202,6 @@ mod tests {
     }
 
     #[test]
-    #[ignore] // Binary support isn't correct yet - buffers don't match
     fn binary_single_column() {
         let one_vec: Vec<u8> = (0..SMALL_SIZE as u8).collect();
         let many_vecs: Vec<_> = std::iter::repeat(one_vec).take(SMALL_SIZE).collect();
@@ -1213,7 +1212,6 @@ mod tests {
     }
 
     #[test]
-    #[ignore] // Large binary support isn't correct yet - buffers don't match
     fn large_binary_single_column() {
         let one_vec: Vec<u8> = (0..SMALL_SIZE as u8).collect();
         let many_vecs: Vec<_> = std::iter::repeat(one_vec).take(SMALL_SIZE).collect();