[GitHub] [incubator-doris] HappenLee commented on a diff in pull request #9856: [feature-wip](array-type) Add array type support for vectorized parquet-orc scanner

[GitBox <gi...@apache.org>]

HappenLee commented on code in PR #9856:
URL: https://github.com/apache/incubator-doris/pull/9856#discussion_r889806014


##########
be/src/vec/functions/function_cast.h:
##########
@@ -1040,6 +1073,69 @@ class FunctionCast final : public IFunctionBase {
         };
     }
 
+    WrapperType create_array_wrapper(const DataTypePtr& from_type_untyped,
+                                     const DataTypeArray& to_type) const {
+        /// Conversion from String through parsing.
+        if (check_and_get_data_type<DataTypeString>(from_type_untyped.get())) {
+            return &ConvertImplGenericFromString<ColumnString>::execute;
+        }
+
+        const auto* from_type = check_and_get_data_type<DataTypeArray>(from_type_untyped.get());
+
+        if (!from_type) {
+            LOG(FATAL) << "CAST AS Array can only be performed between same-dimensional Array, "
+                          "String types";
+        }
+
+        DataTypePtr from_nested_type = from_type->get_nested_type();
+
+        /// In query SELECT CAST([] AS Array(Array(String))) from type is Array(Nothing)

Review Comment:
   here may cast `[Array String]` to `[Array Int]`, but the `string` cast to `int` may lead to `NULL`, how to handle it?



##########
be/src/vec/utils/arrow_column_to_doris_column.cpp:
##########
@@ -236,19 +237,51 @@ static Status convert_column_with_decimal_data(const arrow::Array* array, size_t
     return Status::OK();
 }
 
+static Status convert_offset_from_list_column(const arrow::Array* array, size_t array_idx,
+                                              MutableColumnPtr& data_column, size_t num_elements,
+                                              size_t* start_idx_for_data, size_t* num_for_data) {
+    auto& offsets_data = static_cast<ColumnArray&>(*data_column).get_offsets();
+    auto concrete_array = down_cast<const arrow::ListArray*>(array);
+    auto arrow_offsets_array = concrete_array->offsets();
+    auto arrow_offsets = down_cast<arrow::Int32Array*>(arrow_offsets_array.get());
+    for (int64_t i = array_idx + 1; i < array_idx + num_elements + 1; ++i) {
+        offsets_data.emplace_back(arrow_offsets->Value(i));

Review Comment:
   the offset is offset of `arrow::ListArray`, seems not the correct offset of `data_column` ?



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