apacheGH-43994: [C++][Parquet] Fix schema conversion from two-level e…

…ncoding nested list
wgtmac · Sep 6, 2024 · 7e6cb6d · 7e6cb6d
1 parent 12dddfc
commit 7e6cb6d
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diff --git a/cpp/src/parquet/arrow/arrow_schema_test.cc b/cpp/src/parquet/arrow/arrow_schema_test.cc
@@ -598,6 +598,26 @@ TEST_F(TestConvertParquetSchema, ParquetLists) {
  arrow_fields.push_back(::arrow::field("name", arrow_list, false));
  }
 
+ // Two-level encoding List<List<Integer>>:
+ // optional group nested_list (LIST) {
+ // repeated group array (LIST) {
+ // repeated int32 array;
+ // }
+ // }
+ {
+ auto inner_element =
+ PrimitiveNode::Make("array", Repetition::REPEATED, ParquetType::INT32);
+ auto outer_element = GroupNode::Make("array", Repetition::REPEATED, {inner_element},
+ ConvertedType::LIST);
+ parquet_fields.push_back(GroupNode::Make("nested_list", Repetition::OPTIONAL,
+ {outer_element}, ConvertedType::LIST));
+ auto arrow_inner_element = ::arrow::field("array", INT32, /*nullable=*/false);
+ auto arrow_outer_element =
+ ::arrow::field("array", ::arrow::list(arrow_inner_element), /*nullable=*/false);
+ auto arrow_list = ::arrow::list(arrow_outer_element);
+ arrow_fields.push_back(::arrow::field("nested_list", arrow_list, true));
+ }
+
  auto arrow_schema = ::arrow::schema(arrow_fields);
  ASSERT_OK(ConvertSchema(parquet_fields));
 

diff --git a/cpp/src/parquet/arrow/schema.cc b/cpp/src/parquet/arrow/schema.cc
@@ -674,6 +674,10 @@ Status ListToSchemaField(const GroupNode& group, LevelInfo current_levels,
  // List of primitive type
  RETURN_NOT_OK(
  NodeToSchemaField(*list_group.field(0), current_levels, ctx, out, child_field));
+ } else if (list_group.field_count() == 1 && list_group.field(0)->is_repeated()) {
+ // Special case for nested list in two-level list encoding
+ RETURN_NOT_OK(
+ NodeToSchemaField(*list_group.field(0), current_levels, ctx, out, child_field));
  } else {
  RETURN_NOT_OK(GroupToStruct(list_group, current_levels, ctx, out, child_field));
  }