[GitHub] [arrow] kou commented on a change in pull request #12041: ARROW-15203: [GLib] garrow_struct_scalar_get_value() for scalar from C++ returns value

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kou commented on a change in pull request #12041:
URL: https://github.com/apache/arrow/pull/12041#discussion_r776869489



##########
File path: c_glib/arrow-glib/scalar.cpp
##########
@@ -2039,6 +2039,16 @@ GList *
 garrow_struct_scalar_get_value(GArrowStructScalar *scalar)
 {
   auto priv = GARROW_STRUCT_SCALAR_GET_PRIVATE(scalar);
+  if (!priv->value) {
+    auto arrow_scalar =
+      std::static_pointer_cast<arrow::StructScalar>(
+        garrow_scalar_get_raw(GARROW_SCALAR(scalar)));
+    for (auto arrow_element : arrow_scalar->value) {
+      priv->value = g_list_prepend(priv->value,
+                                   garrow_scalar_new_raw(&arrow_element));
+    }
+    priv->value = g_list_reverse(priv->value);
+  }

Review comment:
       This is a idiom in GLib. This is for performance but this will not be needed here.
   
   `GList` is a linked list. `g_list_append()` is O(N) (N is the number of elements). `g_list_prepend()` is O(1). `g_list_reverse()` is O(N).




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