wgtmac commented on code in PR #466:
URL: https://github.com/apache/parquet-format/pull/466#discussion_r1859998523
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LogicalTypes.md:
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@@ -684,44 +689,58 @@ optional group my_list (LIST) {
}
```
-Some existing data does not include the inner element layer. For
-backward-compatibility, the type of elements in `LIST`-annotated structures
+Some existing data does not include the inner element layer, resulting in a
+`LIST` that annotates a 2-level structure. Unlike the 3-level structure, the
+repetition of a 2-level structure can be `optional`, `required`, or `repeated`.
+When it is `repeated`, the `LIST`-annotated 2-level structure can only serve as
+an element within another `LIST`-annotated 2-level structure.
+
+For backward-compatibility, the type of elements in `LIST`-annotated structures
should always be determined by the following rules:
1. If the repeated field is not a group, then its type is the element type and
elements are required.
2. If the repeated field is a group with multiple fields, then its type is the
element type and elements are required.
-3. If the repeated field is a group with one field and is named either `array`
+3. If the repeated field is a group with one field with `repeated` repetition,
+ then its type is the element type and elements are required.
+4. If the repeated field is a group with one field and is named either `array`
or uses the `LIST`-annotated group's name with `_tuple` appended then the
repeated type is the element type and elements are required.
-4. Otherwise, the repeated field's type is the element type with the repeated
+5. Otherwise, the repeated field's type is the element type with the repeated
Review Comment:
I don't want to add an example for rule 5 because it is already at line 685
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