mapleFU commented on code in PR #466:
URL: https://github.com/apache/parquet-format/pull/466#discussion_r1855484507
##########
LogicalTypes.md:
##########
@@ -684,44 +702,67 @@ 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:
+##### 2-level structure
+
+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.
+
+```
+<list-repetition> group <name> (LIST) {
+ repeated <element-type> <element-name>;
+}
+```
+
+For backward-compatibility, the type of elements in `LIST`-annotated structures
+should always be determined by the following rules if they cannot be determined
+as 3-level structures:
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`
Review Comment:
So, the rule-4 doesn't means like (3), but inner-most element type is
"required" ( not repeated ?)
##########
LogicalTypes.md:
##########
@@ -684,44 +702,67 @@ 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:
+##### 2-level structure
+
+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.
+
+```
+<list-repetition> group <name> (LIST) {
+ repeated <element-type> <element-name>;
+}
+```
+
+For backward-compatibility, the type of elements in `LIST`-annotated structures
+should always be determined by the following rules if they cannot be determined
+as 3-level structures:
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
field's repetition.
Examples that can be interpreted using these rules:
```
-// List<Integer> (nullable list, non-null elements)
+// Rule 1: List<Integer> (nullable list, non-null elements)
optional group my_list (LIST) {
repeated int32 element;
}
-// List<Tuple<String, Integer>> (nullable list, non-null elements)
+// Rule 2: List<Tuple<String, Integer>> (nullable list, non-null elements)
optional group my_list (LIST) {
repeated group element {
required binary str (STRING);
required int32 num;
};
}
-// List<OneTuple<String>> (nullable list, non-null elements)
+// Rule 3: List<List<Integer>> (nullable outer list, non-null elements)
+optional group my_list (LIST) {
+ repeated group array (LIST) {
+ repeated int32 array;
Review Comment:
Still cannot figure out rule3 and rule4 diffrences...
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
