Github user yhuai commented on a diff in the pull request:
https://github.com/apache/spark/pull/14014#discussion_r70030569
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetRowConverter.scala
---
@@ -482,13 +482,105 @@ private[parquet] class ParquetRowConverter(
*/
// scalastyle:on
private def isElementType(
- parquetRepeatedType: Type, catalystElementType: DataType,
parentName: String): Boolean = {
+ parquetRepeatedType: Type, catalystElementType: DataType, parent:
GroupType): Boolean = {
(parquetRepeatedType, catalystElementType) match {
- case (t: PrimitiveType, _) => true
- case (t: GroupType, _) if t.getFieldCount > 1 => true
- case (t: GroupType, _) if t.getFieldCount == 1 && t.getName ==
"array" => true
- case (t: GroupType, _) if t.getFieldCount == 1 && t.getName ==
parentName + "_tuple" => true
- case (t: GroupType, StructType(Array(f))) if f.name ==
t.getFieldName(0) => true
+ case (t: PrimitiveType, _) =>
+ // For legacy 2-level list types with primitive element type,
e.g.:
+ //
+ // // List<Integer> (nullable list, non-null elements)
+ // optional group my_list (LIST) { <-- parent
+ // repeated int32 element; <-- repeatedType
+ // }
+ true
+
+ case (t: GroupType, _) if t.getFieldCount > 1 =>
+ // For legacy 2-level list types whose element type is a group
type with 2 or more fields,
+ // e.g.:
+ //
+ // // List<Tuple<String, Integer>> (nullable list, non-null
elements)
+ // optional group my_list (LIST) { <-- parent
+ // repeated group element { <-- repeatedType
+ // required binary str (UTF8);
+ // required int32 num;
+ // };
+ // }
+ true
+
+ case (t: GroupType, _) if t.getFieldCount == 1 && t.getName ==
"array" =>
+ // For legacy 2-level list types generated by parquet-avro
(Parquet version < 1.6.0),
+ // e.g.:
+ //
+ // // List<OneTuple<String>> (nullable list, non-null
elements)
+ // optional group my_list (LIST) { <-- parent
+ // repeated group array { <-- repeatedType
+ // required binary str (UTF8);
+ // };
+ // }
+ true
+
+ case (t: GroupType, _) if t.getFieldCount == 1 && t.getName ==
parent.getName + "_tuple" =>
+ // For Parquet data generated by parquet-thrift, e.g.:
+ //
+ // // List<OneTuple<String>> (nullable list, non-null
elements)
+ // optional group my_list (LIST) { <-- parent
+ // repeated group my_list_tuple { <-- repeatedType
+ // required binary str (UTF8);
+ // };
+ // }
+ true
+
+ case (t: GroupType, _)
+ if parent.getOriginalType == LIST &&
+ t.getFieldCount == 1 &&
+ t.getName == "list" &&
+ t.getFieldName(0) == "element" =>
+ // For standard 3-level list types, e.g.:
+ //
+ // // List<String> (list nullable, elements non-null)
+ // optional group my_list (LIST) { <-- parent
+ // repeated group list { <-- repeatedType
+ // required binary element (UTF8);
+ // }
+ // }
+ //
+ // This case branch must appear before the next one. See
comments of the next case branch
+ // for details.
+ false
+
+ case (t: GroupType, StructType(fields)) =>
--- End diff --
Probably it is good to explain why we are explicitly matching `GroupType`
with `StructType` (because we are trying to determine if `GroupType` represents
a Struct or just a middle layer?).
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