felipecrv commented on code in PR #37877:
URL: https://github.com/apache/arrow/pull/37877#discussion_r1342745111
##########
docs/source/format/Columnar.rst:
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@@ -487,6 +499,102 @@ will be represented as follows: ::
|-------------------------------|-----------------------|
| 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 | unspecified (padding) |
+ListView Layout
+~~~~~~~~~~~~~~~
+
+The ListView layout is defined by three buffers: a validity bitmap, an offsets
+buffer, and an additional sizes buffer. Sizes and offsets have the identical
bit
+width and both 32-bit and 64-bit signed integer options are supported.
+
+As in the List layout, the offsets encode the start position of each slot in
the
+child array. In contrast to the List layout, list lengths are stored explicitly
+in the sizes buffer instead of inferred. This allows offsets to be out of
order.
+Elements of the child array do not have to be stored in the same order they
+logically appear in the list elements of the parent array.
+
+When a value is null, the corresponding offset and size can have arbitrary
+values. When size is 0, the corresponding offset can have an arbitrary value.
Review Comment:
My intention here is to say that an implementation that trusts `offsets[i]`
when `sizes[i] == 0` is non-compliant and unsafe. I consider that being more
strict on what consumers of list-views can do than saying "go ahead and feel
free to dereference any offset". Being stricter on producers of list-views
doesn't make the consumers protected from malicious or bogus producers.
> ...and perhaps specific instrumentations such as ASan / UBsan.
Being able to pass random list-view arrays with wild `offsets[i]` when
`sizes[i] == 0` is how we can fuzz the implementations and get ASan / UBSan to
catch the mistakes. Well-behaved `offsets[i]` will more likely hide issues than
highlight them.
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