etseidl commented on code in PR #466:
URL: https://github.com/apache/parquet-format/pull/466#discussion_r1826156685
##########
LogicalTypes.md:
##########
@@ -648,49 +648,66 @@ 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
-should always be determined by the following rules:
+Some existing data does not include the inner element layer, meaning that
+`LIST` annotates a 2-level structure. In contrast to 3-level structure, The
+repetition of the outer level `LIST`-annotated 2-level structure can be
+`optional`, `required`, or `required`. For backward-compatibility, the type of
Review Comment:
Is this one too many `required`? Or do you mean to add `repeated` as well?
##########
LogicalTypes.md:
##########
@@ -648,49 +648,66 @@ 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
-should always be determined by the following rules:
+Some existing data does not include the inner element layer, meaning that
+`LIST` annotates a 2-level structure. In contrast to 3-level structure, The
+repetition of the outer level `LIST`-annotated 2-level structure can be
+`optional`, `required`, or `required`. 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.
+ elements are required. In this case, `LIST` annotates a 2-level structure.
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`
- or uses the `LIST`-annotated group's name with `_tuple` appended then the
- repeated type is the element type and elements are required.
+ element type and elements are required. In this case, `LIST` annotates a
+ 2-level structure and the element type is a Struct type with multiple
fields.
+3. If the repeated field is a group (not `LIST`-annotated) with one `required`
+ or `optional` field, and is named either `array` or uses the
`LIST`-annotated
+ group's name with `_tuple` appended, then the repeated type (a single-field
+ Struct type) is the element type and elements are required. This is a
special
+ case of 3-level structure where the names are respected.
4. Otherwise, the repeated field's type is the element type with the repeated
- field's repetition.
+ field's repetition. In this case, `LIST` annotates a 2-level structure. Note
+ that the repeated field cannot be a 3-level LIST whose repetition must be
Review Comment:
```suggestion
that the repeated field cannot be a 3-level LIST, as such a list's
repetition must be
```
##########
LogicalTypes.md:
##########
@@ -648,49 +648,66 @@ 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
-should always be determined by the following rules:
+Some existing data does not include the inner element layer, meaning that
+`LIST` annotates a 2-level structure. In contrast to 3-level structure, The
Review Comment:
```suggestion
`LIST` annotates a 2-level structure. In contrast to the 3-level structure,
the
```
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